Hi Bill, After reading all the stories about the problems of installing a lift motor mount in an M15, I decided to do it the easy way and cut an access hole and install a port. What I did was install a rectangular access hatch between the aft end of the sail locker and the end of the cockpit. It gave me excellent access to the area of the stern where I installed a backing plate (plywood) and then the Fulton lift motor mount.
From reading other postings, a smaller round hatch would probably have done the job as well, however:
how do you install a backing plate through a 8 inch diameter hole? Isn't it a lot easier to work through a larger area? My large hatch now give me a second sail locker for access to items stuck all the way aft. I keep my fenders there; my cleaning bucket and cleaning materials; and I find it a big improvement, because formerly all those items lived in the same space but were hard to get. Now it is just open the lid and reach in.............. I don't remember exactly whose hatch I picked, but WEST Page 467 - Bomar Inspection Hatches - Model 411597 10 1/4" x 14 1/4" flange OD will give you the idea. My feeling was: if I am going to have to cut an access hole to do the motor mount installation, then let's increase utility by making it another sail locker lid. Connie M15 #400 LEPPO