Originally published December 2003
*Moved & Edited September 2017

5/20/2022  IMPORTANT UPDATE!

BED -It TAPE  is now distributed by; Sailboatowners.com (link)

Countersunk/Beveled Hole

Over the years, especially in the last few weeks via PM’s/emails, I have been asked how I bed deck hardware with Bed-It Tape. Late one night I was in the barn staring at a cleat, and a small scrap of clear Lexan, hmmmm…… A drill, counter sink, some Bed-It Tape ( butyl based hybrid elastomer that does not cure, harden or crack), my camera and a few minutes later I had the pics I needed. Sorry it took so long, it just needed to “click” the way I wanted to present it..

Here’s how to bed deck hardware with Bed-It Tape:

Step 1 – Countersink the deck holes slightly and then clean everything with Acetone or a similar fast evaporating solvent.  Be sure your cleaning solvent is compatible with your decks finish.

SITE PLUG: After this article was published, we were forced to develop a marine specific butyl based hybrid elastomeric sealant. Bed -It Tape was specifically formulated and tested for marine use. Bed-It Tape can be found at;  Sailboatowners.com.  Please understand that despite our use of the word “butyl” Bed-It Tape is not a standard “butyl-tape”. Bed-It Tape is a hybrid product utilizing Compass Marine Inc. own proprietary formulation.

5/8″ Countersink Bit

Why on earth do I countersink or chamfer the deck side of the skins?

#1   This practice does a lot to prevent gelcoat crazing. By feathering the edge of the gelcoat, through the use of countersink bit, you are now a lot less likely to start a crack or craze mark in the gelcoat. Gelcoat is an un-reinforced product and because of this its prone to cracking. Sharp right angle holes are a good place for these cracks to begin when you tighten the deck hardware and potentially flex the substrate. Beveling the edge of the hole or feathering it limits the ability of the crack to begin or start. This is why you often see holes drilled into plate glass that will have beveled or rounded edges too.

#2   By creating a bevel or countersunk recess in the surface of the deck the butyl tape has a cavity to fill. Without a bevel the hardware would compress the sealant to about 1/64th of an inch thick after the fasteners are tightened. Marine sealants do have some flexibility but not as much as you would guess. Follow me for a moment; Let’s say you have a marine sealant that has a rating of 400% elongation before break on a 1/64″ thick joint. Simple math shows you that 400% of 1/64″ is only 1/16″ of total allowable joint movement before a joint failure or leak starts. In the case of a stamped stainless steel stanchion base, 1/16″ is not much allowable movement before failure.

#3   By countersinking around the bolt holes you increase the maximum thickness of the sealant, at the bevel, to roughly a 3/32″ depth at it’s deepest point. Using the same math as above 3/32″ X 400% gives you a total joint movement before failure of 3/8″. If a mechanically fastened joint is moving 3/8″ you have more problems than just a deck leak! So 1/16″ allowable movement before failure at 400% without countersinking or 3/8″ allowable movement at 400% before failure with countersinking. Even a small bevel will drastically increase max allowable movement before failure. Countersinking to a mere 1/16″ depth will give you 1/4″ total movement around the bolt before failure. You don’t need a deep bevel to make a large difference between a failure and a seal.

#4   Countersinking is a super easy task and has many many benefits. For instance, you can install the fitting and tighten it down now with no waiting and you can seal deck hardware alone.

I am going to inject some strong opinion here so please move on to the next photo if you don’t want to hear it.

I have a high level of disdain the Don Casey “two step“, “wait to tighten until cure and form a gasket” method of bedding deck hardware. Believe it or not but I’m not a conspiracy theorist. I do however feel as if Don Casey wrote that technique to guarantee boatyards future revenue. (grin & wink)

This is NOT to say that it can’t work though. It certainly can and does work.

“So what’s with the angst RC?”

The problem with the two step method & using a marine sealant is this;

Can the average DIY or yard employee get repeatable results that are reliable and consistent?

The answer to that is very often a big fat NO!

This is not about the idea of forming a layer of sealant between the fitting and deck being a bad idea, but rather about the EXECUTION, which can be very difficult to perfect and get repeatable & reliable results, being the bad part of the idea..

Think about it like this;

• If the sealant cures, to form a “gasket”, and you then move the bolt while tightening it down on the “second step”…. It can break the seal and leak…
• If you create a gasket too thick, and then can’t get the mechanically fastened hardware tight enough against the deck, because of compression resistance in the new gasket, the hardware will move, and the sealant will eventually fail and leak.
• If you don’t let the sealant kick/cure just right, which is very difficult, it can all squeeze out and again it can leak. Why is this so difficult with a sealant? Because most commonly used marine sealants are temp and environment cured. This means that humidity & temperature change the duration & rate of cure so it is not easily repeatable.

Honestly, I mean no disrespect to Mr. Casey, he writes excellent, excellent stuff and I am a huge fan. Unfortunately this method for bedding deck hardware is perhaps some of the most difficult to execute advic to achieve in the real world.

I have witnessed far too many cases of core rot due to both DIY & professional “two step” bedding procedures than I would have liked to.

“But RC what makes it so hard?”

The biggest problem is that most marine sealants are moisture cured and you really have no way to know what state of cure they are in. The edges of a fitting may be at the right state but the middle of the fitting still wet & unchanged. Moisture cured sealants change states in a very unpredictable manner.

With a quality marine grade butyl it is more of a “one step” procedure because the consistency of the product is not changing states and all your doing it tightening slowly or over time to let it “displace” out from under the fitting to the point where it stops oozing out.

So where did I lean this countersinking method?

I learned this from a worker at Hinckley Yachts back in the 80’s.. Morris, Sabre and other top quality builders have known this secret for years but many of the big production builders are still either too cheap, or just don’t know about it. This extra step takes all of about 30 seconds per stanchion but apparently it’s too much “extra” work for most builders.

OK I’m done with my rant…for now…

Lifting Eye Backing Plate (outside the boat)

If by chance you’re reading this, and are still not convinced about countersinking, this is a lifting eye I installed in 2002 for an inflatable RIB dinghy. To do this install all I did was bevel the outer hull with a countersink bit, clean the surface with acetone, install the fitting with 3M 101 polysulfide and tighten it down once. I then cleaned up the goop that squished out and called it a day.

This fitting has been bone dry now for fifteen years and resides below water, as in completely submerged, when the dinghy is floating.

EDITED: 2/12/2016: This lifting pad eye us still bone dry and not leaking a single drop, at 15 years, in a fully submerged application. The process you use is a huge part of the success or failure rate.

Morris Yachts Countersinking !

I Also Beveled The Lexan

Press Into Deck Hardware

Install Butyl Cones

Press Hardware Onto Deck

Use Proper Backing Plates!

Click Here: Bed-It Tape

The Electrophysics CT-33 Moisture Meter

I’ve always been a big proponent of boat owners, and more importantly boat buyers, owning a moisture meter. I don’t suggest this because I want every DIY boater to think they are a surveyor, or to try and circumvent the surveying process, that is not my point at all. I suggest it because in all seriousness the meter above paid for its self the first time I used it to rule out just one boat. Essentially, a survey for 30+ footer can run $600.00 or more these days and whether or not the boat passes you pay the surveyor the $600.00+.

More often than not you find a boat and it looks great on paper and on Yachtworld.com. You then meet the broker, bring your spouse and you both get an extreme case of boat buyers lust. “She’s just perfect!” Your heart gets racing and you begin to imagine how much fun it will be to own her. But wait a minute, she looks great on the surface but what’s underneath? Is she in need of hidden big $$$ repairs?

Any good and reputable broker should offer to bring along a moisture meter, if not just ask. Sadly though many less helpful or thorough brokers claim they don’t have one or don’t know how to use one. More often than not they don’t actually own one. This to me is like going to a family practice doc who does not own a stethoscope. If this is the case … well.. your choice? I know many good brokers, who have meters, and who go over the deck and cored hull before even listing a boat. Ask all the questions! If you don’t ask them, you won’t get any answers.

So what can you do to protect your self from paying for surveys on boats with saturated decks or hull core? Buy an Electrophysics CT-33, or its sister meter the J.R. Overseas GRP-33, read this blog and the manual, do a Google search of “moisture meters for fiberglass” and then go for it.

When we bought our current boat I looked at over 50 boats, meter in hand. It did not take me long to rule many of them out due to severe moisture issues. Many times I would not even involve the broker and instead would do a drive by, find a ladder, and at least circle the chain plates and deck fittings near the rail. I don’t suggest boarding any boat without a broker, I didn’t just leaned the ladder up and did some cursory checking, I have been able to rule out many boats this way without wasting a brokers time. Heck on many “drive by’s” I never even had to get out of the car! I saw some nice boats and some basket cases but unfortunately some had some really hidden deck problems even though they were in good cosmetic condition.

The CT-33 is sold by Electrophysics in Canada currently sells for $160.00 and you’ll need a calibration block for another $10.00. The US distributor, J.R. Overseas, has an exclusive deal for all US sales and they sell a meter that is slightly altered, has different scale graphics but that is essentially a very similar meter. The J.R. Overseas GRP-33 sells for $325.00. The CT-33 sells for less.

Electrophysics CT-33 (LINK)

This photo shows the first thing to do when you turn it on. Simply flip it on and hold it vertically in mid air. The needle should read zero. This is an initial calibrations check.

Please DO NOT buy a moisture meter if your intent is to circumvent the survey process. To master the use of one takes time and should be used with soundings, something many DIY’s don’t have the ear for and other measures to cross check the moisture meters findings.. Using one to rule in boats that may be a good candidate for a survey or to rule out boats that have a pegged meter all over is fine and can save you money.

Copper Calibration Block

In this photo the calibration block is laying with the copper face down and away from the meter. This face down orientation is what you use when checking the calibration

Testing The Calibration

When the meter is placed atop the spacer and copper faced calibration block the meter should read exactly 14%. My camera was slightly off center but the meter does read spot on when you are directly over it.

So if the meter reads zero when holding it in mid air and 14% when placed atop the calibration block and spacer it’s ready to use and in perfect calibration.

Meter Reading of Dry Test Panel

Now I know what you’re probably thinking “it’s already wet”? If you thought that you’d be wrong. This 6% reading is actually about as bone dry as you’ll ever get on either solid or cored fiberglass using the CT-33. Using this meter any reading between 0% & 15% is considered dry on fiberglass.

Remember this meter is primarily designed for the many different species of wood. It may also be used on man made materials such as fiberglass. You’ll need to reference the scale found at the end of this page for fiberglass interpretations/translations.

Contrary to popular belief moisture meters don’t actually read moisture. They actually read capacitance. This capacitance reading is then transposed, onto the analog display, into a relative moisture reading.

Reading 5/8″ Solid Fiberglass

Here is a piece of 5/8″ solid fiberglass I laid up to cut thru-hull backing plates from. It is bone dry and has never left my shop or been wet other than atmospheric moisture. As you can see it reads a little over 8%.

Different materials can have different readings. This piece of known dry 5/8″ solid glass actually reads slightly higher than a dry sandwiched balsa core. Both of these chunks have been sitting in my shop for well over two years, stored right next to each other, so the environmental controls were identical. No need to worry though as any reading on fiberglass between 0% & 15% is considered dry with the CT-33..

Water Mist Sprayed Onto Surface

I wanted to illustrate just how sensitive these meter are and to impress upon potential meter owners why the deck surface must be bone dry before using a moisture meter.

I simply used a misting bottle of water and sprayed the surface of the cored deck chunk to simulate dew or rain. I then used a terry cloth towel in an attempt to dry the surface before taking a reading. It was clearly insufficient.

The CT-33 Scale For Fiberglass

This is the scale for translating meter data. It’s is fairly straight forward. The scale on the left is for reading wood, or a wood cored laminate and the scale on the right is for reading solid fiberglass. As you’ll notice a 30% moisture saturation in wood or a cored section is only equal to 3% total absorbed moisture on a solid fiberglass with no core.

Core rot, degradation and the physical failure of the core can begin at about a 20% reading on the CT-33, sometimes sooner, which is in the high moist range. A pegged meter is indicating a moisture content in the core of about 35% or more!! If boats were made out of water this would be one thing but a core, with even close to 35% water content is not a good sign.

Some other important things to remember:

Moisture meters read metals and display it as moisture. If you want to take reading bellow the waterline you’ll need to scrape away bottom paint in order to get an accurate reading. This is a bad idea and best left to your surveyor. If you want to check for core moisture bellow the waterline do it from inside the hull on areas around seacocks etc.. I do not suggest that you use your meter for bellow water applications, with a solid un-cored hull, as these readings can be very misleading and are best left to a pro to interpret.

Moisture meters can not read frozen water. There is no benefit in even bringing your meter to a boat in the dead of winter. Along those same lines if a surveyor says he can survey a boat for you at 20 degrees F and get moisture readings walk away. Temps should be well above freezing, for a while, before even considering moisture readings.

Always find the lowest reading you can on the boat to use as a baseline. Many times on sailboats you’ll find some dry core right above the wind speed & depth gauges if they are mounted on the cabin.

Look for differences in deck moisture readings. Diminishing changes in readings as you move away from a deck fitting are good indicators that the deck is wet around the fitting and that it is leaking or has leaked.

Most every boat has some deck moisture so don;’t be too alarmed at some “moist” readings. Readings in the moist range are certainly areas of concern but I would suggest bringing in a surveyor if you like the boat. If on the other hand the meter is pegged in multiple areas sch as mast bases, chain plates, genny tracks, bulkheads and other high load areas this is a boat that is probably safe to walk away from and continue looking.

Remember this is not for you to become an expert just to prevent you from spending $600.00 needlessly on a basket case boat. A few years ago I knew of a boat that had been surveyed almost ten times in two years on the market. She had wet decks, a saturated rudder and hull core moisture around the thru-hull penetrations. Each time the potential buyer either paid a discounted rate to “buy” the previous survey usually half price but it varies or to have a new one performed. A simple CT-33 purchase for under $200.00 would have saved these buyers some serious money. Each buyer could have ruled this boat out rather quickly with a little knowledge.

If you don’t feel comfortable buying and using a moisture meter by all means please don’t. A little common sense goes a long way and is all that’s necessary. Buying a meter when buying a boat will get you well on your way to saving money on unnecessary surveys.

If the $179.00 price tag (varies with exchange rate) is still killing you it is very easy to sell it when your done by listing it on any of the sailing forums.

How many times do you need to fork over $600.00+ when looking for a boat before you invest in a moisture meter. Don’t laugh I know some who have coughed up close to 2k in the search for a new vessel and the surveyors loved every penny of it.

WARNING: Use of a moisture meter, by a DIY, should only be done to determine if the boat is worthy of  continuing on with a full survey or to track changes in your own vessels decks or hull. This article is not, and was not written, nor intended, as a means for you to replace or circumvent a professional survey. This article is intended to help you use a moisture meter to potentially uncover boats which are clear lemons and separate them from vessels that are worthy of pursuing further.

High Moist

This is an example of a high moist range reading on an O’Day. This deck is not yet destroyed but any further leaking needs to be curtailed asap or it will be ruined shortly. Because of the critical location, next to a chain plate, this should be attended to and the core removed and repaired sooner rather than later. There are some ares of a boat that you certainly don’t want wet or even high moist.

Utterly Saturated Reading

This is a very bad example of exactly what you don’t want to see, a totally saturated core. This boat lives on a mooring and this is one of the primary mooring cleats. Most would assume there is likely some serious delamination going on and a degrading or degraded core.

When this core was dug into  by the owner it was found to be less damaged than would have been expected based on the reading. It was only dug into after spot soundings indicated some delamination. Meters can read metals and in this case a backing plate so this reading was not as accurate as one would like it to be. This is a prime example of why you need to practice with the meter and confirm what lies beneath.

Remember the degradation and physical rotting of the core begins at around 20% on the CT-33. The longer it has been above 20% the more likely are the odds for a total failure and delamination of the skins but this can still take a very long while. I have seen decks with 25% readings going back 10+ years be taken apart only to find that they were damp, but still very, very structurally sound. Always incorporate spot soundings and core samples before digging into a deck.

Saturated Core

This is an example of what a saturated core looks like during the rotting process. If you look ahead of the chisel you can see how the balsa just turns to mush when you touch it with the chisel. This was a deck penetration under a teak hand rail that leaked due to improper bedding.

30% Wet Core Reading

This is the adjoining deck section to the photo above with the chisel. As you can see the color of the balsa is telling you how wet it is. If you scrape out this core and compress it between your fingers it drips water like a sponge would.

At this stage of rot (early) the core is still tightly bonded to the skins. If this moisture were allowed to continue the color of the balsa would continue to darken and literally rot away leaving no structural strength.

The Epoxy Supplies

Most all boats have some sort of “core” in the decks. Whether it’s balsa, plywood or some of the foam cores all can eventually absorb water from a leaking deck penetration. A leaking deck, especially with wood cores, can lead to core rot and eventually delamination of the deck and loss of structural rigidity.

Sailboats especially can have hundreds of holes drilled into the deck for cleats, stanchions, blocks, winches, genoa tracks or many other mechanically fastened and through bolted or screwed in items.

Unfortunately most builders do not take the time, nor have the patience, to protect the core from moisture. Most builders also fall short in their bedding techniques, choosing in favor of cost cutting measure that you get to deal with a few years beyond the warranty. The “can’t be seen, must not be there” mentality certainly rings true in the category of deck hardware installations.

The re-bedding of deck hardware is a time consuming task but one that can save your five, six or seven figure vessel from loosing 25% to 50% of it’s market value due to saturated and rotted decks.


 There is no method better than potting the holes with thickened epoxy to prevent core damage, if you have core where hardware passes through it. This project  is easy but also quite time consuming. Once done correctly you will never have to worry about water getting into your core again.

These are the epoxy products I often use to pot deck holes. I sometimes use System Three Epoxy products too but for this article I used West System. West System epoxy products are very easy to find and use. I use a #205 hardener #105 resin & Colloidal Silica or “Cabosil” as the filler or thickening agent.

In order to inject the resin into the holes I use the West System syringes.

Brad Point Drill

When drilling into fiberglass the proper tool is a must. This is a brad point drill and it will create a clean, no chip hole in gelcoat provided you use a few tricks.

TIP: The main trick with brad points into gelcoat is to start the drill in reverse. This trick also works well with hole-saws. By starting in reverse it allows the outer cutting edges of the drill to cut cleanly through the gelcoat. Once through the gelcoat you can then switch the drill to forward and complete the hole without chipping any gelcoat off the surface.

Dremel Bit #115

This is one of two bits I use to remove the core. It is a 5/16″ diameter head with a 1/8″ shank. It allows a just right amount of core removal to seal the deck from moisture.

Enlarging An Existing Hole

In order to complete this article I used a scrap piece of end grain balsa deck structure. I wanted to use a scrap piece so that I could make cut-a-ways to show the inner workings and what actually happens on the inside of the deck.

Here I’ve drilled three holes;

• One hole for the #115 bit,
• One hole for the #654
• One hole that will remain as 1/4″ with no epoxy fill.

The center hole, as you can see, has been counter sunk. This was originally a 1/4″ hole that I over sized to 5/16″ to make the #115 bit fit into it. Over sizing holes in fiberglass can often result in an “oops” and some serious deck chipping.

TIP: Here’s the trick to over sizing holes:

#1 Countersink/chamfer the hole to just barely beyond the width of the drill you will use for the over sizing, in this case 5/16″. If your countersink bit is new and sharp get in the habit of using reverse, not forward, when countersinking fiberglass. Forward will remove too much material, far too fast, if you are not careful.

#2 Place your brad point drill in the chamfered hole and start in reverse. You will cut through the top skin only and have a nice clean hole. You do however need a brad point drill set. You won’t find them at Home Depot and will find them a Rockler or on line. This is the quickest and cleanest way to bore the top skin without the drill wandering or causing serious gelcoat chipping.

Drill For Making Over Sized Hole

Here’s my 5/16″ bit that I used to enlarge the hole on the top skin. Again, do not drill all the way through the deck just drill through the top skin.

Bottom Holes

This photo illustrates that all the holes below deck are still 1/4″ even though the middle hole has a 5/16″ diameter on the decks surface. This leaves as much of the deck skins intact is as humanly possible.

Inject Non-Thickened Epoxy First

I know I said “thickened epoxy“, and we’ll get there, but first it’s a good idea to inject clear mixed non-thickened epoxy into each hole. By doing this you allow the less viscous, resin only, without thickener, to penetrate the surface pores of the core. this creates a better and stronger final bond.

In order to do this I inject straight mixed epoxy into each hole with a syringe. I then let it sit in each hole for about 3-4 minutes, suck it back out with the syringe and then squirt it back into the mixing cup where I add Cabosil (colloidal silica) to thicken it.

Remove Trapped Air Bubbles

Here I have re-injected the holes with my West System syringe. I did cut about .5 cm off the tip of the syringe which makes the hole bigger to accommodate the more viscous thickened epoxy.

TIP: The green stick you see is simply a piece of weed-whacker line. This is a very simple and cheap tool for popping any trapped air bubbles and aiding in migrating bubbles to the surface so you leave behind any voids.

All you do is move the weed-whacker line in, out and around the hole until you have no more air bubbles rising to the surface.

Wipe It Down

Of course if I were doing this on an actual boat I would have first pre-taped over the holes, like the photo above, & then used my countersink bit between my fingers to remove the tape from the holes. This method protects the deck and the countersink carves out a nice clean hole in the tape.

In this photo I simply used a rag with Acetone to wipe away any over flow. Use tape and it will go much smoother and cleaner. I simply forgot when photographing this..

#654 Bit – Cut-A-Way of Potted Deck Hole

After I removed the tape I re-drilled each of the holes with my 1/4″ drill and then counter sunk the two holes that had been potted.

This is a picture of the hole I made with the 1/4″ #654 Dremel bit. The hole is clean and precise with plenty of separation between the epoxy and the core. Both the top and bottom holes through the deck skins remained at 1/4″ for a factory original look and feel yet this is much better than how it would have come from the factory.

Explanation of Countersinking

“RC why on Earth do you countersink or chamfer the deck?”

#1 It does a lot to prevent gelcoat crazing. By feathering the edge of the gelcoat, through the use of countersink bit, you are less likely to start a crack or craze mark in the gelcoat.

#2 By creating a bevel or countersunk recess in the surface of the deck the marine sealant or Bed-It Tape has a cavity to fill. Without a bevel the hardware would compress the sealant to about 1/64th of an inch thick after the fasteners are tightened. Marine sealants do have some flexibility but not as much as you would guess.

Follow me for a moment:

Let’s say you have a marine sealant that has a rating of 400% elongation before break on a 1/64″ thick joint. Doing the math shows us that 400% of 1/64″ is only 1/16″ of total allowable joint movement before a joint failure or leak starts. In the case of a stanchion base 1/16″ is not much allowable movement before a sealant failure.

By countersinking around the bolt holes you’ll increase the maximum thickness of the sealant, at the bevel, to roughly a 3/32″ depth at it’s deepest point. Using the same math as above 3/32″ X 400% gives you a total joint movement before failure of 3/8″. If a mechanically fastened joint is moving 3/8″ you have more problems than just a deck leak. So, 1/16″ allowable movement before failure at 400% without countersinking or 3/8″ allowable movement at 400% before failure with countersinking.

Even a small bevel will drastically increase max allowable movement before a sealant failure. Countersinking to a mere 1/16″ depth will give you 1/4″ total movement around the bolt before failure. You don’t need a deep bevel to make a large difference between a failure and a seal.

#3 Countersinking is really a very simple step and has numerous benefits. For instance, you can install the fitting and tighten it down now with no waiting. This means you can seal deck hardware alone and not wait for a marine sealant to change states or cure.

I am going to inject some strong opinion here so please move on to the next photo if you don’t want to hear it. I would discourage anyone from using the Don Casey “two step“, “wait to tighten and form a gasket” method of bedding deck hardware with a curing marine sealant.

Is this because it can’t or won’t work? Absolutely not? Is it because I don’t like Don Casey? Absolutely not! Don is a great guy and tremendous asset to the boating community. Then why?

In my experience this method is probably one of the leading causes of deck core rot on the planet. This is NOT to say that when done properly it won’t work, just that it is VERY, VERY, VERY, VERY difficult to actually do this properly. Many a DIY and pro have messed this up and ruined decks as a result.

Think about it:

If the sealant cures, to form a gasket, and you then move the bolt while tightening it down on the second step…. You will likely lose. If you create a gasket too thick, it cures, and then you can’t get the mechanically fastened hardware tight enough, against the deck, because of compression resistance, the hardware will move, flex and also fail, so again, you lost the battle.

I mean no disrespect to Mr. Casey, he writes tremendous marine books and articles, but the method he made popular is very difficult to nail down repeatably because cure-rates change with humidity, temp and far too many factors to get a good reliable procedure you can easily repeat.. I have witnessed far too many cases of core rot due to DIY & professionals using a two-step bedding procedure than I would have liked to.

So where did I lean this countersinking method? I learned it from Hinckley Yachts… Sure this extra step takes all of about 30 seconds per stanchion but apparently it’s too much extra work for most production builders.

Not Much Stretch

This bolt hole has no bevel at the deck level. It was loosened and raised the same amount as the previous bolt, to illustrate how much difference in allowable movement one can attain through the simple step of countersinking.

Alternative Methods

This photo represents two other ways of doing the same job. Personally I’m not a huge fan of either one as much as the previously mentioned methods using the Dremel bits.

Why don’t I like these methods as much?

#1 In method #1 I drilled an over sized 1/2″ hole clean through the deck and then filled it with thickened epoxy. By over drilling the entire thickness you have removed the deck skins which are the major structural component in the I-beam. End grain balsa has very little strength along the grain, which is where the epoxy adheres to in an over drill. Picture splitting fire wood. You split with the grain and if flakes off nicely. Epoxy adhered along the grain can do the same.

If you tried to split across the grain or pull balsa apart via the end grain it would be very, very difficult and this is why it is called end grain balsa and why the deck skins are laminated to the end grain not parallel to the grain of the wood.

The areas highlighted in red, the deck skins, are thinner than they appear in this cropped photo, especially on light weight sailboats. In this example your only means of structural support are the circumferential bond between the top and bottom skins as the area in green is very, very weak comparatively speaking and would really rely on the backing plate.

I have seen two failures of total over drills in my life. Theoretically speaking, when used with proper backing plates it should hold but if your balsa is even just moist your entire bond will only be the thin area of the two skins. It should be noted that epoxy does not adhere well to wet core this is why it is critical to seal the deck before it gets wet.

#2 In method #2 I have only over drilled the top skin but left the bottom skin intact. This is stronger than method #1. With the top skin gone it too is less strong than leaving most or all of the top and bottom skins intact and creating a captured plug.

#3 Using either method #1 or #2 leaves you with a larger hole on the UV side of the deck. Some stanchion bases or hardware may not entirely cover the larger hole completely and epoxy does not like UV. This means an additional step of gel coating the repair.

It’s entirely up to you how you seal your decks all I can do is present the pro’s and cons, as I see them. Of these two methods I prefer method #2 but I still prefer the Dremel procedure far and above both methods #1 & #2.

That said ANY of these methods is far superior to not sealing the core off from potential leaks.

New Port Lights For an Older Boat

Choosing to install new portlights sounds easy but can be a complicated decision process. There are numerous companies out there building poor products that sell for big money and others building beautiful products that sell for a reasonable amount. My decision involved lots of research and investigation into the minute details of portlight construction. Many of the larger, well known, companies did not stack up when I began to dig into the small details. In the end I chose New Found Metals as my portlight supplier.

This project is not for the boater who barely knows the difference between a Phillips head and a slotted head screw driver and is about a 5-6 on the 1 to 10 complexity scale. The task is straight forward and does not require artist like skills, akin to blending and color matching gelcoat, but this is a long and time consuming task.

Our boat has 8 ports and I figure this project took me a little over 45 hours of time. Hopefully this article will save you some time and you can learn from any my mistakes and use my time saving tips. I figured each port would take about two hours but I was a little off.

I do hope this article helps someone considering new ports or who needs some guidance installing NFM portlights.

As always click on any photo to make it larger. This article is quite long and includes more than 40 photos.

Reading Exterior Offset

Before moving on to the next measurement you need to write down your measurement or transpose it, as I did, to my calipers. The exterior offset reading was rounded up to 13.5mm.

The picture shows the accuracy a little bit off but it was hard to hold the caliper and square in one hand and the large Nikon DSLR in the other and keep it perfectly in place..

Reading Interior Offset

Do the same for the interior offset and write this number down. I rounded this up to 9mm.

Measuring Port Total Thickness – Exterior View

You can see the caliper clamped to the widest point of the port in this exterior view.

Actual Depth

My caliper shows this hole at 7/16 but most of the others were 5/16 just as NFM says they are. Plan on a quarter inch of room, as a safety margin, and you’ll be fine. This bolt depth measurement obstacle is a bit tedious but it prevents any screws from being visible on the out side of the portlights. It also minimizes the chance of leaks by having less exposed holes in the trim ring..

Step 2 – Removing The Old Ports

Lucky for me, the Beckson ports had been installed with butyl tape and a double sided foam weather stripping, and not one of the high tenacity polyurethane sealants like 3M 5200. All I needed was to pry the trim rings off the cabin sides and then apply a constant pressure to slowly stretch the butyl and remove the ports. keep in mind these ports were installed in 1979 and this boat has been nearly all the way around the world and back. Interestingly enough it was the Beckson gaskets that had been leaking and not the butyl tape.

For removal of the trim rings I used a heavy duty putty knife. Prior to using this putty knife that I have softened / dulled the sharp edges so I would not scratch the cabin sides.

If your ports were installed with 3M 5200 please be very, very careful removing them. The tensile strength of 5200 is anywhere from 40-700+ PSI and the fiberglass to gelcoat bond is roughly 400-500 PSI. If you are not careful and you try to force the ports off the boat you can literally tear the gelcoat clean off the substrate.

In my opinion, garnered over many years of removing this stuff, 3M 5200 has no place being used to hold a portlight into a boat! Use products like 3M 5200 at your own risk..

If you’re at a loss with 5200 you can try using products such as De-Bond to soften it. Sometimes heat will help to soften the 5200 too but do be careful using heat guns. They can burn the gelcoat if not used carefully and kept moving at all times.

Clean Up The Surface

To clean up the residue I used my boat chisel. My boat chisel has been tuned to minimize scratching the surface. If you’re not skilled in the use of a chisel or dulling or sharpening them the right amount, find another way of removing the vast amount of sealant or you could scratch your hull.

Once I had the majority of the surface clean I used mineral spirits, it works well on butyl.I then followed up with Acetone, wearing chemical resistant gloves, to do a final cleaning.

Taping Off The Inside

Here’s the Gorilla Tape (duct tape) I used when compounding the cabin sides to prevent any messes inside the boat..

Temporary Duct Tape To Cover The Openings

TIP: This is for keeping your boat dry while the work is in process. I chose to remove all the old ports then prep, cut, drill, chamfer and bore the openings all at the same time but needed a way to keep the boat dry as I was going through the installation process.

I have been using Gorilla Tape, from the makers of Gorilla Glue, and it is far and away the finest duct tape I have found for this. It’s thick, does not leave much if any residue, and sticks tenaciously to just about anything.

To seal the port openings, until you can install the ports, start at the bottom of the port opening and work your way up like clapboards on a house overlapping each seam by about 1/2″. If you worked your way down water will get in but if you tape from the bottom up the seams over lap so they don’t drain into one another.

Even though the boat was covered I didn’t want to take any chances, and yes Gorilla Tape will keep rain out.

Why I Needed to Replace These Ports #2

As I said some were worse.. This hinge literally crumbled apart after I removed the port. In defense of Beckson these plastic ports lasted about 30 years, but ideally should have been replaced about ten years ago.

These Beckson ports were no longer safe for any sort off-shore sailing. One big wave surely could have broken them, in the brittle state they were in, and allowed the boat to take on green water.

Step 5 – Template/Jig & Hull

For this step I needed to cut the openings for the NFM ports slightly larger than the Beckson’s had been. The new opening also needed to accommodate for the portlight spigot. I used the NFM template (shown in the previous photo). As I mentioned earlier this is really a should have item for this job.

To cut the openings I chose to use the NFM template as my router guide and use my Ryobi laminate trimmer with a bearing guided flush cut bit. Using a jig saw, hand saw or sanding drums just seemed like an awful lot of work, though some have actually done it this way.

This photo shows the template clamped to the inside of the cabin sides.

Vacuum Tip

I know this has nothing to do with NFM portlights but the little Rigid 6 Gallon wet dry vacuum, from Home Depot, at $39.00 is a great investment for working on your boat. I actually got rid of my big shop vacs and now have three of these little 6 gallon models. One for the barn, one for the garage and one for working on boats. It’s tiny, powerful and easy to lug up and down ladders.

TIP: I generally ditch the hoses that come with shop vac’s and visit a local vacuum shop for an adapter and about 20 feet of central vac hose. This makes using a cumbersome shop vac a pleasure. The home attachments are better too. The horse hair brush (pictured) is one of my favorites. Within 25 minutes I had totally cleaned the interior of all the routing dust with the horse hair brush and the central vacuum hose. It’s a handy little combo for sure.

The Laminate Trimmer

This little battery operated laminate trimmer was a $49.00 bargain. As a marine business we own lots of heavy-duty professional grade tools from Hitachi, Porter Cable, Milwaukee, Makita & DeWalt but I often find my self reaching for this inexpensive Ryobi. This article was even written well before Li-Ion batteries came out and this little trimmer worked well even without a Li-Ion battery.

I have yet to kill one of these budget level tools, and I actually use some of the Ryobi stuff professionally.

Whether you chose to use a Ryobi, DeWalt, Hitachi, Bosch etc. a small laminate trimmer, vs. a router, is the way to go.

The NFM $29.00 Counter Bore Is Worth It

Once you’ve drilled the 3/8″ holes you’ll need to counter bore into the cabin side exterior 1/2″ deep to accommodate the bolt studs on the trim ring. My cabin sides were 1/2 inch deep so I had to go all the way through, which is fine.

The NFM counter bore has a 3/8″ guide pin, to match the previous 3/8″ holes you drilled, and it bores it out to 5/8″. It is well worth the $29.00 and is a very high quality & clean cutting tool.

45 Degree Bearing Guided Chamfer/Bevel Bit

Having learned the art of bedding fittings from some of the guys at Hinckley Yachts I believe in the bevel/chamfer and tighten once method for most things. I don’t generally subscribe to the “tighten over a few days to create a gasket” method.

Beveling the edges of the holes does a few things:

• 1)It forces bedding compounds into the hole, like a funnel, as you tighten the fitting.
• It creates an o-ring of sealant that is about 6-8 times the thickness of what would be there without a bevel.
• It allows you to tighten the fitting all the way down without coming back days later to do so which can break the seal that has already cured around the bolts threads.
• It creates a surface area that forces sealant against and around the bolts threads or shank.
• It prevents gelcoat crazing and checking around the bolt holes.

To use the bevel method for the ports I again used a laminate trimmer and a 45 degree bearing guided bevel/chamfer router bit. The router bits guide bearing fits in the 5/8″ hole so I used the laminate trimmer for those holes too.

On these ports, using the butyl, it is very, very difficult to tighten them down all the way at once. I tightened the ports over two days, which is short enough so my polysulfide sealant did not fully harden, but long enough to fully compress the butyl.

IMPORTANT: I differ from the NFM instructions on this particular procedure. NFM says to tighten over a few days letting the sealant harden to form a “gasket”. Here is my explanation of why I do it the way I do:

I’ve been bedding fittings, tighten once or before the bedding is dry, this way for a very long time and never once had a re-leak. The idea that tightening a fitting all the way down squeezes out all the sealant is just not true. Take for example the aluminum valve cover on the Volvo 5 cylinder engine used in the V-70 series and others. This valve cover uses no gasket and only a thin layer of Permatex (Silicone) is required to seal it. You apply the Permatex, install the valve cover, and torques the bolts. Valve cover gaskets are under positive crank case pressure and deck fittings or ports are not.

I have used the above method (bevel then tighten at once) on underwater fittings as well and still never had a leak. It’s your choice as to how you seal your ports and I’m merely telling you how I differ from the manufacturer on this one point.

EDIT: If I had to do this job over again I would not use the NFM black butyl tape. I would instead use Bed-It Tape which is gray and is formulated not to “bleed” or do what is called “cold flow”. Using Bed-It Tape will completely eliminate the need to use both a sealant and a tape. The light-gray color of Bed-It Tape is far less messy than the black tape from NFM and it does not stain.  Bed-It Tape is also specifically formulated to resist cold flow or creep in warm temps. Bed-It Tape was specifically formulated for bedding marine deck hardware, after this article was written back in 2005. Bed-It Tape offers a wider working temp range, has much less propensity for cold flow or creep/bleeding, has a higher level of chemical resistance and more elongation before failure than cheap “butyl tapes”.

The Chamfer / Bevel

Here is a close up of the beveling or chamfering. It runs all the way around the port and around each bolt hole. Every bedded fitting on the entire boat is, or will be, as I get to them, bedded using this method.

Most times I just use a drill and countersink bit but for big holes like this a laminate trimmer is a good option. While that bevel may look big it’s really only about 1/16 of an inch.

Dry Fitting & Leveling The Ports #2

Checking the left side of the port for level. You can see, when the camera pulls away, how slight the bevel is. It’s there but hard to see in this photo.

IMPORTANT: On a boat with no clear cabin line, for the ports to align with for level, you may need to set up a ladder and back away from the vessel.  Climb the ladder and use the old-school MK I eye ball as your determination of what looks level.

TIP: Click any photo to make it larger.

NFM Teak Trim Rings

These are the NFM teak spacers. They run about $40.00 each but are well worth it. Do yourself a favor and do any finish work or varnishing before you install them.

Ready For Butyl

In this photo I’m getting ready to level the port and clamp it down in order to begin applying the butyl.

Wrapping The Butyl

EDIT: When this article was written Bed-It Tape did not yet exist. One of the main reason Compass Marine Inc. developed Bed-It Tape was due to the low quality and continual bleeding and staining of the NFM black butyl. The NFM butyl tape is a cheap run-of-the mill butyl formulation.

If I were doing this job today, it would be done using only Bed-It Tape and no marine sealant. Bed-It Tape can be purchased at the link below.

Purchase Bed-It Tape

In this picture I’ve already forced one round of the NFM butyl into the gap and I’m working on my second round. I found a silicone kitchen tool that worked really well for forcing the butyl into the grove without it sticking to the tape.

With the teak spacers it’s very difficult to wrap the ports spigot first, as NFM illustrates in their instructions, before inserting it. Instead, I chose to clamp the port, level it, then install the butyl from the outside.

Again, I varied from the NFM instructions on this issue and installed the butyl from the outside, not the inside, but both methods will work.

TIP: I applied the butyl from the outside for one major reason. I don’t believe in sealing any fitting, installed on a boat, from the interior side of the vessel. If you do get an external leak, between the fitting and hull, you’ll want to know about it.

If I sealed or bedded the cabin side (inside the boat) of the fitting I may be trapping water or worse diverting it somewhere else because it can’t escape out the back side of the fitting. Diversion of water by, internal sealing, creates an almost impossible scenario for tracing external leaks.

Even though this boat does not have cored cabin sides, kudos to CS-Yachts for this move, I still chose to only seal from the front of the port to prevent trapping any water in there that could potentially freeze, expand and do damage in the cold Maine winters..

In short, I did not want any sealant between the ports inside flange and the hull only the outside flange, trim ring and the spigot. I was able to get about five pieces of butyl around the spigot drain and two laps of butyl around the rest of the port, but I can assure you, this was NOT easy.

Squeezing in the butyl and seating it took almost 50 minutes per port before I even began to install the trim ring and bolts or clean up the “squeeze out”.

If your previous ports were installed with silicone you should, at a minimum, wet sand until you get NO water beading when you spray the surface with water. There is no chemical that will remove the embedded silicone from the gelcoat other than sanding. If anyone knows of one please email me! I’ve already tried just about every chemical known to man, even stuff only body shops can buy that is specifically intended for removing silicone. IT DOES NOT WORK ON FIBERGLASS either because it’s too porous or it eats the gelcoat.

TIP: If water beads around where the trim ring is to seal it’s not clean. I use a spray bottle filled with water for this test and do it every time I re-bed a fitting. Do not skimp on this detail.

Second Round Seating The Butyl

In this photo the second round of butyl is just about ready. You do not want to leave the butyl too thick here or it will squeeze out the outer edges of the trim ring and make a huge mess..

I had to redo my first port because I used too much butyl when installing it.

EDIT: If you use a gray butyl tape like Bed-It Tape there will be no need for the marine sealant.

You need enough to make a seal, and to squeeze out between the trim ring and the spigot, but not so much that is squeezes out the outer edge of the trim ring..

Prepping The Trim Ring – Butyl

Before you can even begin to install the trim ring there are three steps that need to be taken.

The first is to actually clean the trim ring as stated above. The second, pictured, is to wrap butyl around each of the trim ring studs. I found out the hard and messy way that you do not want HUGE globs of butyl around the studs or it will squeeze out the top of the trim ring and make for some messy clean up. I actually re-did my first port because of this.

Seeing as I countersunk each hole I wanted just enough to fill the bevel and a touch more, that’s it.

To make the butyl thinner I simply rolled it between my fingers while pulling slightly at the same time, like you would do with a joint, If your not familiar with this action a visit to any college campus will teach you. I then cut it using a knife and a silicone cutting board and wrapped it around each stud.

Setting The Trim Ring

Once the butyl is in place and you’ve prepped the trim ring with a polyurethane or polysulfide, of your comfort and choosing, it’s time to set the trim ring.

If you used the method I outlined it is possible to remove the clamps, for a brief period, after you’ve seated the butyl tape so you can install the gooped up trim ring.

Once the clamps have been removed slide the trim ring over the ports spigot/flange and re-set the clamps. Do not over tighten them and use just enough pressure to get the machine screws started from the inside.

The DAP CAP

TIP: This handy little item is called a DAP CAP and it’s available in the Home Depot paint department. It serves two purposes.

1- It can be used to clean up the excess sealant that squeezes out.

2- It fits over the end of an open tube of caulk to seal it for future use.

NOTE: The DAP CAP does not fit Sikaflex nozzles but does work on 3M brand tubes.

Tighten The Machine Screws

This photo shows the clamp still in place and the bolts inserted about two to three turns. At this point, if you have subscribed to this particular installation method, you may now begin tightening the machine screws in an alternating pattern. If you subscribed to the NFM method of creating a “gasket” follow their instructions.

It’s important for the seal, and even distribution of sealant under the trim ring, using either method, to tighten the machine screws so the trim ring compresses as evenly as possible.

I find it considerably easier to tighten until you meet some resistance, then stop, wait and repeat in 15 minutes or so. I would move onto another project and come back fifteen minutes later and take another few turns. Torquing the trim ring screws slowly allows the butyl to compress slowly and evenly rather than force tightening all the screws immediately.

You’ll notice the Tef-Gel around the bolt head which made for easy turning with minimal grabbing of the two surfaces. Once done, I simply wiped this excess up with paint thinner.

After the Chisel

By letting the 3M 101 set up overnight it was pliable enough to remove with the chisel and yet still soft enough to get a clean edge with a solvent wipe down..

The Final Result

Now that the ports are in I was finally able to remove the cover and snap a photo.

TIP: Since I installed these NFM ports, I’ve treated the port gaskets religiously with 303 Aerospace Protectant. This has resulted in rubber gaskets that look and perform as well today was when they were installed 14 years ago. There has been absolutely no sticking of the gasket to the frame thanks to the judicious use of 303 Aerospace Protectant. Each time I open the ports I squirt a bit onto a rag and wipe the gasket before closing the ports. It adds minimal time but ensures the port gaskets will last for a good long time.

EDIT: It has now been 15 years since this project was completed and the ports look as good today as the day they were installed. They have performed flawlessly, never leaked a drop of water, and really lead to a lot of aesthetic compliments. The only gripe I have about this installation is the cheap black-butyl tape from NFM. It is low quality, stains and bleeds in hot weather. If Bed-It Tape had been used, none of these issues would exist.

Good luck and happy boating!