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Author Topic:   Filling bolts holes in Transom of 16'7 hull
NHKatama posted 11-11-2002 10:22 AM ET (US)   Profile for NHKatama   Send Email to NHKatama  
I have removed the old engine from my 16' 7 hull and have two engine bolt holes and 4 from an old steering cable bracket (ouch). I need to fill these holes before I have the boat Gelcoat nicks patched and Hull buffed. I am not sure of the bestway to address this. I thought of using epoxy with hardwood dowels to fill the holes, but have heard that gelcoat will not stick to the epoxy. The other thought was to just fill the holes with 3M 5200., but not sure that is the best way either, I am now thinking of using Poly Resin with the dowels. Anyone out there have experience with filling holes in their transom, I would like your opinion on the best way to fill these. Thanks ~~PT
newt posted 11-11-2002 11:10 AM ET (US)     Profile for newt  Send Email to newt     
NHKatama, do a search on this topic. There are countless (some very recent) threads about filling holes.

I would fill with epoxy. It's easy, strong, and I have not experienced a problem with gel coat adhesion. If it matters, I have only used the spectrum patch kit - never tried other gel coats.

Tom W Clark posted 11-11-2002 11:53 AM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     

There are probably many different ways to fill those holes, some better than others. In a perfect world you would be able to wave your magic wand and restore the transom to its condition before the holes were drilled. In reality you can patch the holes by thinking of how the transom is constructed and using the same materials to fill the holes.

The transom is made of a core of two layers of 3/4" plywood covered by fiberglass skins on both sides. This plywood is a marine grade most likely made of Douglas Fir, a relatively soft wood. You do not want to use a hardwood dowel to plug the hole because it will not compress at the same rate as the plywood transom.

What you do want to do is glue in a plug of wood so the grain of the plug is running sideways and not in and out as it would with a section of dowel.

If it were my I would cut some plugs from some 3/4” plywood or some 3/4” solid stock. I really don’t think it matters too much what kind of wood you use but I probably would not use something hard like like oak or maple. If you just have a scrap of a 2 x 4 laying around that would be fine too if it was fir, hemlock, larch or something similar.

The reason this is so important is that it is very common for the transom to compress when the outboard mounting bolts are installed. Look at the mounting holes you have now and see it the is some dimpling where the old bolts were. You do not want to patch the holes with a dowel, drill new holes and install your new outboard and then then tighten the bolts up and watch the carefully patched gel coat pop out because the dowels are resisting the compression.

When you glue the plugs in you want them to be wetted on all surfaces so they form a solid mass with the transom itself. You can use almost any kind of glue you have. 5 minute epoxy would be nice because it sets so fast. Polyurethane glue like Gorilla Glue would be good too. You could also mix up some polyester resin and use that.

Gel coat will stick to epoxy so long as the amine blush is scrubbed off with soap and water. All in all it might just be easier to use polyester resin if that is what you have laying around. Fill the holes all the way to the surface of the transom and then route out to a depth of maybe 1/16” the area over the hole and a little of the surrounding surface. Fill this area with gel coat patch paste and level, sand and then buff out to the same sheen as the rest of the transom.

Gel coat patch paste is NOT epoxy (not to be confused with MarineTex, which is an epoxy putty). Gel coat or gel coat patch paste is polyester and very easy to work with. The color matched patch paste kits from Spectrum would be just right for finishing off these holes in your transom.

NHKatama posted 11-11-2002 09:59 PM ET (US)     Profile for NHKatama  Send Email to NHKatama     
What is the best way to search for a topic on this forum, I looked for a search area but did not see one.

Thanks, ~~~PT

acassidy posted 11-12-2002 07:13 AM ET (US)     Profile for acassidy  Send Email to acassidy     
At the top of each forum, there is a drop down bar with topic from up to the last 2 year. Click that and click the button, wait a few seconds for it to load, and then ctrl + F for find.
DJS posted 11-12-2002 09:55 AM ET (US)     Profile for DJS  Send Email to DJS     
Try this for searching.

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