Wondering about the best way to plug old motor mount holes in an inflatable with a stainless curtain over fiberglass/plywood transom.

Should I fill with MarineTex, and call all's well?

Or should I coat holes with MarineTex, and smear stainless bolts with same, set, and rest easier?

Temps are well below ideal for using MarineTex, but can apply a space heater if need be. Should I be looking at another product?

Have used MarineTex with excellent results on fiberglass transom repairs in the past, but the stainless transom curtain on this inflatable gives me pause...

Any advice is most appreciated.

Or should I coat holes with MarineTex, and smear stainless bolts with same, set, and rest easier?

This is what I would do..not much work for a better piece of mind.

I just went to their website and it explains in detail what products to use for different applications.. I need to repair some loose fasteners on my Whaler rails and this sounds like the correct product line.

The marine tex will do just fine under compression not so well under tension. Whatever you use be sure that the plywood is dry. If it is not take the time to dry it. Then slighty thin some epoxy resin with acetone and coat the inside of the holes, after that sets up coat them with unthined resin and let that set up before you apply the filler.
By the way remember that you can apply epoxy over polyester but not the other way around.

You don't say if you plan on re-using the same holes. I'll assume you are. Dry is a must (like blackmouth said). But as important is that you must be into good wood. If the hole(s) had silicone or other sealer originally you'll need to redrill or sand the inside of the hole to remove the old sealer. Once that is done, marinetex will work. You can heat the holes one at time with a hair dryer and then a lamp after if you like. The stuff is great if prepared correctly. I have even used it (more than once) to rebuild broken aluminum transmission cases with success.

Thanks much for the excellent advice. Wood is in excellent shape from what I can see in the holes, and dry, and I've prepared holes in accordance with the Marinetex website's recommendations. Excellent info there--thanks for the tip. Should've thought of that myself.

Holes won't be reused. But: there's a speedo cable running over the top of the transom and I'm wondering if I should run it through one of the holes before applying epoxy. Mixed feelings...probably won't.

Plan to leave an electric oil radiant heater next to transom for 24 hours or so before plugging holes, to raise ambient temperature. Garage is airtight enough that it should do the trick.

Motor to be mounted is hanging there; I'm guessing I should also drill new holes (doesn't match with old holes) and mount it at the same time, all one one fell swoop of epoxy application. Hmm...how far will a 2 oz. container of Marinetex go?

--mja

I wouldn't use the marine tex on the new holes, but would plug the old with it. The new holes can be sealed with a flexible sealant. There are numerous ones available...silicone is probably the most commonly used, but not the strongest, if strength is an issue. 3M makes marine sealant (5200 fast cure....or 4200 slow cure) awesome stuff but spendy. Just coat the inside surface of the new hole(s) with the sealant of your choice, then a thin coat on your new clean bolt shafts....you're sealed. I'd leave the cable over the top, but whatever. Good Luck