75 separator rebuild

I was thinking of going at the transom core from the inside. Use a circular saw to cit through one layer of the glass, use a grinder to bevel both sides of the cut before removing the skin, then gently remove the inside skin. Use the Fein to get under the existing wet ply, but not damage the outer skin. Replace new CPES treated ply a la vacuum bag and epoxy with the filler of your choice. More epoxy on the inside skin after being prepared, pull another vacuum to re-apply the skin. Build up with 1", 2" and 4" tape around the cut referenced at beginning of the post. This was a way I would replaced rotten core under nonskid sections on sailboats. Those patterns were always a challenge to match.

Anyhow, maybe worth a try here?

normally, the first piece of ply goes from corner to corner, the second piece covers the drive hole with extra. i cardboard template the first piece and fit, coat both sides and edges, let dry, scuff with 80, coat ply and use bolts thru gimble holes and tie off holes to clamp along with extended vice grips, at times i will put kickers in from the stringers to the ply to help in clamping

Here is a pic of transom prior to planing! Eric, how am i going to attach the wood to transom. can you give me a step by step and the best products to use , thanks again. and yes this is the best tool for cutting parts out

I vote to leave it.Could it be there for a reason like drain plug support? That is a drain plug there right?

first, how thick is the mounting area? and are there 2 pieces of ply bonded together? normally you'll have a layer of gel, then glass and finally 2, 3/4 pieces of ply back to back
you'll notice the mounting studs on the gimble are 2.5 or so long. rmember the forces that are pushing a 3500 lb boat are all transfered thru the transom unlike an inboard. good qaulity ply...not marine, cpes highly recommended in this area.
As I said, I make my pattern, pre fit the ply, drill my mount holes, coat liberally to waterproof, mix it on the cool side, lay the piece up in there and go to town with clamps, inluding any thru holes i will use pre determined bolt and nuts to clamp, including tie down holes....anything that has a hole...I have long arm vice grips that i will use thru the gimble hole to reach other ares and at the corners I will tie in kickers screwed to the stringers or anything solid

btw, a portable hand planer would whack that down in under a minute

at what age do we become dirty old men?

If the resin in question is simply pooled resin (no glass) then I would say remove it. It will be fairly brittle, as resin doesnt have much strength without the glass fibers. Its most likely a result of a sloppy build process.

Just use standard 3/4" ply. All of the home dpot and lowes plywoods are made with external wood glue. Make sure it is untreated though. Thats what the cpes is for. When I laminated my lift mount and my stringers I used plain resin and a ton of clamps. Use thickened resin for bedding as mentioned by Tim.

the plain resin with hardner will hold them together, thats what your saying, then glass back and sides that goes to boat, then with thickened epoxy attach to hull. all treated with cpes of course then glass over top. how much glass over top, size, and layers? thanks for putting up with my ignorance.

Makes sence what your saying Benj, you just got your post in before i finished typing mine what typ of mat in between boards

it appears that when they built your boat, time wasnt spent on the transom, to me it looks as if they mereley put 2 pieces of ply together in the gimble area only, and thats why i feel you have stress cracks.....spread the load accross the entire transom with the ply on the first piece corner to corner, and then the second piece as big as you can without obstructing any other component that may be back there. You probably have a deck hanging off the back also,
the one pic you have does not show so much in strength, just a mount pad for the gimble, cheesy, normally most wood back on the transoms are never coated, just painted....cost effective when building at the manufacturer....you have the opportunity to build it stronger and add the personal touch and be worry free when running the boat.
post more pics of the transom if you can

eric lavine wrote: ...spread the forces of the outdrive. under power the outdrive has a tendency to pull at the top and push at the bottem of the transom.

On a sterdrive, where does the load of thrust apply on the boat? Is it directly to the transom like an outboard, or is ultimately pushing forward on the motor mounts? I've heard the term "stringer drive" used in reference to OMC sterndrives, just curious how the Mercruisers are set up.

Jeff, hook in the hull has been discussed here at length- try a search.

Edit: nevermind.