Originally Posted by schultzfactor
SamSam: I was actually thinking of 2X40hp?
I'm thinking you are going to have issues of displacement, which means the size of the hulls weren't designed to float as much weight as you've already added with wood, fiberglass, etc., much less any big motors.
You should put it in the water right now, before you add any more weight, and see how it floats.
Here's a chart that rwatson made on motor weights in kilos
So, put it in the water and have two guys stand on the back transoms to simulate two 40 hp outboards, while you stand where the center counsel is going to be. Plus put two full gas tanks aboard, two batteries, an anchor and equivalent weights for the center counsel and all supplies like a cooler of food, drinks, ice, fish gear, etc. Lay a few pieces of plywood on where the decks will be. If you plan to take any passengers, add some seating weight and have those passengers get on now. The two guys on the transom don't count as passengers, as they are 'outboard motors' for the moment. It would be best to rig a couple lines to the bows so the 'outboard' guys can lean way back over the water and heavily jump up and down on the transoms, better simulating real outboards.
As long as it's glassed and the wood is sealed, clean fresh water won't hurt anything, it will dry off. But it will give you a pretty good idea of how it floats and how much weight you can add, if any, and where you can add it.