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Author Topic:   Repairing transom holes
DavidM posted 02-11-2002 09:23 AM ET (US)   Profile for DavidM   Send Email to DavidM  
I have four bolt holes through transom into splash well on a 17'. Any suggestions on how best to fill and repair them?
JBCornwell posted 02-11-2002 12:07 PM ET (US)     Profile for JBCornwell  Send Email to JBCornwell     
Best is an opinion thing, but here is what I would do.

1. Coat the inside of the holes with epoxy, let it soak into the wood.

2. Hardwood dowel same size as hole, 1/2" shorter than the depth of the hole. Coat with epoxy and drive it in so that it is 1/4" below the surface at each end. Let cure.

3. Fill 1/4" deep holes with celcoat repair material. Let cure.

4. Sand level and finish with progressively finer grit until the repairs can be polished to match gelcoat.

Red sky at night. . .
JB :)

reelescape1 posted 02-11-2002 12:19 PM ET (US)     Profile for reelescape1  Send Email to reelescape1     
I'm going through the same right now with my 22' OR.....this is from Chuck Bennett at Whaler:

"If you are going to fill the old holes and, most likely, will not be drilling around the same holes, I would recommending filling the old holes with a polyester resin, milled fiber and chopped fiber mix. Allow this to cure and then grind through the gelcoat approx 3/4" all of the way around the old hole and place a layer of 2 oz fiberglass mat into the area (using polyester resin), fair and re-gelcoat. This will prevent the holes from cracking out (due to vibration).

"If you are going to drill the new holes right next to the old holes, you might want to take some hardwood dowels and epoxy or glass them into place and then apply a layer of 2oz fiberglass mat over that.

"When installing a new motor, just make sure the inner and outer areas of the mounting holes are sealed with a good bedding compound or marine sealant. Whaler uses Sikaflex 921 at the factory."

[I added quotations around what I presume is Chuck's material, and eliminated the many inconsistent and hard-coded line breaks, which I abhor because they severely reduce the readability of text--jimh]

kamml posted 02-11-2002 07:26 PM ET (US)     Profile for kamml  Send Email to kamml     
I just had four engine mount holes filled on my Montauk using the dowel method. It appears that the dealer used plastic dowels rather than wood. I intend to seal them up like the previous post suggested. Ken
bwmenemsha posted 02-11-2002 08:05 PM ET (US)     Profile for bwmenemsha    
would this procedure also work for plugging holes in deck through hull where the john was removed on my menemsha???...thanks
Tom W Clark posted 02-11-2002 08:07 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
The (wood) dowel system may work, especially if it is really well sealed with epoxy or resin or whatever, but I still do not like it nor do I recommend it. End grain wood is going to have far less compressibility than the rest of the transom and think there is the risk of having the patches become "highlighted" with a crack all the way around the patch and the patch standing proud. See my comments in this thread:

jimh posted 02-11-2002 09:53 PM ET (US)     Profile for jimh  Send Email to jimh     
I know the Whaler factory advice always mentions making repairs with polyester resin, the same material that the hull was molded with, but I temd to think that this is often because of economic factors for them.

A laminate fabricator (like Whaler) uses resin by the train car load, and thus epoxy's higher price has very significant impact on their costs. They also have literally tons of polyester resin around, so naturally they tend to use it to make repairs, too.

Epoxy is generally acknowledged to be a better adhesive. It is more suitable for repair situations which involve secondary bonds.

Another advantage is the ability of make small batches of it with some accuracy. The chemistry of epoxy is different than polyester resins.

An epoxy mixture needs proper quantities of two reagents to form the final resin.

Polyester resin is in the process of hardening, it is just kicked into overdrive by a catalyst. The reaction proportions are usually ounces to eye drops, a ratio hard to control.

I think the shelf life of epoxy is likely to be better, too. I have a four year old can of polyester resin on the shelf, and I would not be surprised to find it has hardened by itself the next time I open it. This is just my own guess, not scientific analysis.

The water proofing of epoxy is better, too.

The down side to epoxy, other than cost--which does not have a big impact in the quantities we are talking about--it that there is a legend that it is hard to topcoat with gelcoat. This is true if the amine blush is not thoroughly washed away with soap and water.

The other downside to epoxy is potential for allergic reaction. Gloves are recommended when handling epoxy resins.

I also was surprised that the factory recommended grinding out the surfaces and adding layers of cloth (mat) to avoid a brittle area. This same technique could be used with epoxy resin repairs. It may be good advice in areas like the transom with there is the potential for a lot of stress and perhaps some movement.


lhg posted 02-11-2002 10:34 PM ET (US)     Profile for lhg    
As you know Jim, I am a fan of the "easier to use" polyester resin and Marine-Tex type products. It would seem to me that if the boat is made of polyester resin, it should be repaired with it. I particularly like the water solubility and easy clean up of Marine-Tex. When I read Whaler's "official" instructions, I wasn't surprised at all and saw that it related to their prior hull repair instructions.

Adding chopped fiberglass fibers to the resin, to make a "mash" is one of Whaler's tried and true methods, which duplicates the chopper gun glasswork used in the hulls. It hardens to a really tough, non-brittle material. Also, the glass matting over the holes re-inforces the glass skin, much like re-bar in concrete, and is also incredibly tough.

As many know, the full transoms used on the Whaler Drive models are actually "after the mold" shop glasswork, also using additional plywood and polyester resin with woven glass matting, covered with gelcoat. Mine has held up beautifully, completely undetectable as post-mold work on the outside, with no signs of failure at all on the inside, where the polyester resin soaked glass matting is actually exposed. I've often marveled at what a good job the factory did in filling in the original notched transom.

I think their instructions for filling engine bolt holes is probably "ultra professional", the way they would do it at the factory. But it sounds like it is also time comsuming work, more than most do-it-yourselfers are willing to put in.

DavidM posted 02-12-2002 08:57 PM ET (US)     Profile for DavidM  Send Email to DavidM     
Thanks for the detailed advice.

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