Plugging Motor Mount and Core Drill Test Holes

[86RinkerV153]

Picking up my new motor today and hoping to start the install. I need to fill two approx. 1/2" holes for the previous outboard mount bolts as well as three 1/4" core test drill holes (bad advice from mechanic to go from outside on those) and a few really small ones from a transducer.

​I have heard on the larger ones to get a matching dowel that fits tight and coat it in 3M 4000 and tap it in, wondering people's thoughts on that?

​Is there another preferred or acceptable technique on the smaller (1/4" and less) holes?

​For the old motor mount ones should I coat and reinstall those bolts and torque them down instead of the dowel method?

Don't have time or experience with fiberglass or harder to get materials, so would prefer simpler solutions if they are safe.

Old motor was a 40 hp, new is a 60 on a 15' fiberglass runabout FYI.

 

[sheboyganjohn]

If you are trying to do cheap and dirty the dowel method would work, but I would use 3M 5200. For the smaller holes find a stick of Marine Tex. It is a two part epoxy stick that you just cut a chunk off, mix and apply. It is the consistency of playdough. Use something to force it into the holes. There will be air in the hole that will keep it from going in if you just try and put a big wad in at once. Might even want to put the dowels in so they sit a bit low in the hole and fill over the top with the marine tex.

 

[gm280]

I have no idea what your present mounts actually look like without any pictures. But if I were doing the project, I may even consider replacing them with all new material being how you talk about a lot of holes in yours now.

If you post a picture or three of your mounts, we can better understand what you are talking about. But rebuilding new mounts couldn't be too difficult and that would be my direction without seeing yours. Then you know they will be solid and absolutely secure as well. No filling holes or using dowels or anything like that, that can possible lead to failure later on. JMHO

 

[86RinkerV153]

I have no idea what your present mounts actually look like without any pictures. But if I were doing the project, I may even consider replacing them with all new material being how you talk about a lot of holes in yours now.

If you post a picture or three of your mounts, we can better understand what you are talking about. But rebuilding new mounts couldn't be too difficult and that would be my direction without seeing yours. Then you know they will be solid and absolutely secure as well. No filling holes or using dowels or anything like that, that can possible lead to failure later on. JMHO

I was probably unclear in that I was referring to two 1/2" holes for outboard mounting bolts that are unlikely to line up with the new motor. So, holes in the transom, not I/O mounts.

 

[gm280]

I was probably unclear in that I was referring to two 1/2" holes for outboard mounting bolts that are unlikely to line up with the new motor. So, holes in the transom, not I/O mounts.

Sorry probably my mistake reading your initial comment. I would mix up some polyester resin Peanut Butter or even epoxy resin Peanut Butter, whatever you like, and mix in some 1/4" or 1/2" chopped fiberglass and even some Cabosil into the mixture and fill in the holes. Then fair them out after they cure. It will be solid as a rock. JMHO