O'25 motor mount
We also upgraded to a new 9.9 4-stroke (from a Mariner 15), deciding that the original motor mount might not be up to the increased weight/torque of the new outboard. In considering how to mount the new outboard, we discovered in our recently-purchased 1983 O'Day 25 that only the portside of the transom had been strengthened for mounting outboards, and that our transom suffered core-rot/delamination because (20 years ago) a 2" thru-hull for remote-control cables had not been re-sealed to protect from moisture penetration. After soliciting a lot of opinion, we decided to remove completely the old motor mount and start anew. We chose the Garelick Model 71091 motor mount, backed internally with an 18" square of 1/4" aluminum, and externally with 1/2" starboard, attached with six ss bolts, fender washers and locknuts, with liberal 5200 sealant around the mount, backing surfaces and bolts. Our method is not proven by experience because we're still on hard completing other aspects of refit. For what it's worth, we ignored suggestions ranging from 1) keep the old motor mount, 2) move motor to starboard side, 3) use Git-rot, 4) cut-out the rotten core and re-core the transom entirely, or 5) use 3/4" marine plywood or 3/8" stainless large sheets for the internal backplate. We've heard opinion both that we haven't done enough and that we've far exceeded what is necessary - we'll see. Garelick wasn't helpful with advice. We're still working out some issues, such as the remote electric-start and control-cable setup and the recharging plan for the outboard alternator. Good luck!
