[abl1111]

Will that's a damn good question ! I have an I/O and did not have to worry about bolting an outboard thru the transom.

I cannot answer your question because I do not know how the epoxied holes would handle the strain of an outboard motor. The epoxy is string as sh_t, the larger washers seem like a good idea; but I would not do anything like what you're talking about until I got a solid confirmation from someone who is 'in the know'.

Actually, rather than the washers, I would think that (2) 1/4" stainless plates or (4) 4"x4" stainless plates would give a lot more support than the washers.

It is an interesting question though - anyone have an opinion ?