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Author Topic:   Repairing Holes in Transom - Caution!
browning20ga posted 02-28-2002 06:52 PM ET (US)   Profile for browning20ga   Send Email to browning20ga  
I finally got a good coat of gelcoat on my transom after filling old motor mounting holes and through-transom holes that were from the original cable steering bolts. Sanded new gel-coat starting with 240 grit working down to 1000 grit. Mounted [Cook Manufacturing Co. Power Tilt and Trim] and lifting eyes; still doing okay. Then I installed 2 SS U-bolts that go through the transom with nuts on the inside, these are located in the area of the old steering holes. (I don't know if these are standard, or an aftermarket item installed by a previous owner). After I tightened the nuts to a point where the lock nut was flush with the end of the bolts like they were before, apparently compressing the foam core, the dowels that I epoxied in the holes pushed out, poking out the gelcoat paste that I had filled the holes with before spraying with gel-coat.

Sorry to be so wordy, but if you are going to plug holes (where there isn't wood core) with dowels, I would suggest using a short piece of dowel inserted in both sides of the hole with air space between (or a material that would compress) that would compensate for compression if installing hardware in the area. Hope my SNAFU helps someone in the future.

reelescape1 posted 02-28-2002 07:07 PM ET (US)     Profile for reelescape1  Send Email to reelescape1     
I'm re-powering my 22' as we speak(?). The glass man did mine this way: He re-drilled the holes a little oversize, ground an area about 2" around the holes, epoxied a HARDWOOD dowel in place (approx. 1/8"-1/4" below flush on both sides), applied a ~2-inch mat with resin over this area (supposed to be the waterproofing step), sanded, finished, filled with some type of putty, sanded, sprayed gel coat.
Tom W Clark posted 02-28-2002 07:29 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
This is a classic mistake and is exactly why I have counseled over and over again NOT to use a dowel. You should ideally plug a hole with whatever used to be in there. The grain should be running in the same direction as the wood it is going into, in the case of plywood, any direction except in/out is OK. If it's the plywood backed portion of the transom, use a plug made from plywood or the wood the plywood was made of (some sort of softwood like fir or even lauan)

In the case of the foam cored portion of the transom, an epoxy patch on both sides but not continuous all the way through the transom will allow the area to maintain the same compressibility it originally had.


You are probably in a better position in that your holes are in the plywood part of the transom, but still, a hardwood dowel is not going to compress as easily as the plywood.

dscew posted 02-28-2002 07:35 PM ET (US)     Profile for dscew    
Tom: is the transom not plywood through the full width? If not, where does it get its strength? I thought most boats had a solid piece of thick plywood running across the entire transom.
Tom W Clark posted 02-28-2002 07:44 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     

No there is not plywood everywhere, only in the motor mounting area, usually the flat center portion of the transom. Refer to your wood locating diagram for your specific hull. There are other pieces of plywood in there as well usually for pony motors, light mounting, ect.

reelescape1 posted 03-01-2002 07:03 AM ET (US)     Profile for reelescape1  Send Email to reelescape1     
I assumed the plywood part is what he was asking about because thats where motor mounting holes would be (unless maybe a kicker bracket). Before I started my re-powering I inquired as to the proper repair also. While I value the advice given on this board I also know that any repair will be A REPAIR....a lot depends on what the repairable part has been through before (water intrusion, poor previous repairs, etc.) Here's what Chuck Bennet at Whaler Service reccomended as the CORRECT ways (2 choices) to repair motor mounting holes in the transom.....this is a cut and paste of his response to my question.

"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 2-oz. 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."

jimh posted 03-01-2002 08:20 AM ET (US)     Profile for jimh  Send Email to jimh     
[Editied posts to improve readability. --jimh]
Chesapeake posted 03-01-2002 12:18 PM ET (US)     Profile for Chesapeake  Send Email to Chesapeake     
Darrell. Sorry to hear of the problem, but also sounds like you are adept to repair well. Thanks for the heads up.

How did the pinhole repair mentioned on your previous post work out? Where you able to ultimately diagnose the problem? Moisture? With all the discussion in Chain Saw Whaler, it has made me think constantly about making repairs to an old hull in light of the likelihood of moisture (significant?) being retained in the hull.

Incidentally, how did you shoot your gelcoat? HVLP or conventional spray equipment? What tip and nozzle sizes, generally speaking, do you use and does Spectrum give you pretty good advice on tip size and thinning?

Kind of curious as I have some repairs in mind. I do most of my finishing with an HVLP gun (and I am thinking of getting one of those little touch-up guns for small repairs).



browning20ga posted 03-01-2002 01:52 PM ET (US)     Profile for browning20ga  Send Email to browning20ga     
First I want to thank Tom W Clark, "reelescape1" and "kingfish" for all your excellent advise. Bob, the second coat went on much smoother but I can't say exactly why, I did reduce the acetone on the second coat from 20% (max. recommended thinning) to about 10% and I did let the transom air dry 24 hrs. (previously dried until it looked dry). As far as equipment I used a middle of the road Craftsman gun (used the tip that came with the gun) and a Craftsman 2hp. compressor equipped with a water trap and a regulator. Shot gel-coat at 35#. From my very limited experience, gel coat is funny stuff to work with, don't think of it as paint. For one thing it doesn't flow like paint, I had a couple spots I wanted to build up so after spraying I brushed some on from the pot, the way it is laid down is the way it stays. Like all repairs the next time around will be a lot easier. Overall I'm very happy with the results I got using gel-coat and would highly recommend Spectrum Color products. Don't be afraid to use gel-coat, and the gel-coat past is great to "top off" holes and if your final sanding of a spot gets a little thin you still have some "color" underneath. And if you sand down to far you won't be into epoxy and leave an ugly spot. The best advice you can get is enclosed right here in this post by Tom and "reelescape1".
Thanks again to all, Darrell
Tom W Clark posted 03-01-2002 02:37 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     

I think you are going to be OK because you are filling the holes from a twin motor installation and installing a single. The new motor mounting bolts are not going to be next to the patched holes.

But if the holes were from an old non-standard bolt pattern motor and you were then installing a new motor with the holes near the repaired holes, then you are going to have a problem. A dowel with the grain running parallel to the clamping force of the bolts is going resist the compression far more than the transom itself and create a hairline crack around the patch if not pop it out right.

Chuck Bennett's advice in exactly this scenario is not so good. The fact that it comes from him and Boston Whaler (and he has given out out lots of good advice) does not mean it is correct, even if that word is spelled with capital letters. His advice represents an opinion like anybody else’s including mine. The fact is, there is no correct nor incorrect advice, just advice some that may be better than others. There are more than one way to accomplish anything.

In the case of using a dowel to fill a hole, it is going to be easier and more convenient to do so because doweling is so readily available. But you have to respect the properties of different materials and sometimes a greater attention to detail is warranted. It is simply more work to use a plug instead of a dowel, but in this scenario, I think it is wise to do so.

Chesapeake posted 03-01-2002 05:29 PM ET (US)     Profile for Chesapeake  Send Email to Chesapeake     
How important is the complete structural integrity of these holes? Would it be reasonable to include an expansion joint in the middle of the hole as one would with concrete or on a long brick wall? If so,hmm, how about cutting a yellow foam ear plug in half and inserting it or some kind of silicone caulk in the middle of the hole and then patching both sides with epoxy? Crazy idea?
reelescape1 posted 03-02-2002 07:27 AM ET (US)     Profile for reelescape1  Send Email to reelescape1     
Thanks Tom, I guess time will tell...I'll definately post if there is an issue in the future.

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