The subject is a 74 20 cc with some problems

[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 ?

[optiguy]

The proper backup washer or backing block can only be determined by the comperssion strength of the core material and the thickness of the fiberglass. Some of the most common errors made by people are the use of square washers and round washers that are too small. No matter what size you use, make sure that some type of bedding compound is used. This is most important with square backing plates as the corners have a habit of cutting into the laminate and causing faliures over the long term.
Bill

[Scott]

Great comments ...and guess I'm old school

WOOD IS GOOD [img]/images/graemlins/grin.gif[/img] [img]/images/graemlins/cool.gif[/img] [img]/images/graemlins/grin.gif[/img]

I am curious to see how these composites hold up over the long run ....But it is somewhat daunting to see damage to these composite hulls that are only a few years old [img]/images/graemlins/frown.gif[/img]

[Tarpinmon]

Thanks everyone for your imput I guess I found the common concensus is to go with wood. I read an article that was saying that the delamination factor is greater with a composite,sounds like the resin bites into the wood a little better. Has anyone ever seen this on boats, Ive seen it on surf boards. Well I guess Ill be leaning towards wood, Question though what type of plywood should i be using I heard people say Marine grade Plywood. where do ya get this stuff? Is this the stuff at Home depot treated with cca? thanks again

working on the single boat theory.. [img]/images/graemlins/grin.gif[/img]

[optiguy]

Any good lumber yard should be able to order marine grade plywood. Don't use any other type of plywood as the glues used to make it are not as strong. Also the quality of the plys and void content is better. As far as the resin "biting into the wood better", that's not really true.
Most failures can be attributed to improper use and application. I can go on about this for hours after 30+ years of boat building and repairing. If you have any specific questions, just ask.
Bill