My 24' pontoon is rated for 115hp. It currently has 40hp. I am tempted to beef up the transom with some triangulated braces that would carry the forces better to the pontoons. My target top speed is 30mph, and I do not think 115hp would do it. From reading other posts it looks like 24mph is what I would get with 115hp.
Considering the size of the boat and after seeing the massive engines that are put on fishing boats, I am convinced the coast guard hp limit is only related to the transom strength and not a safety issue from over powering a small boat.
My first thought is to install a brace between the bottom engine mount on the transom to the upper portion of the pontoon. This would keep the transom from twisting when turning the boat. I figure the transom is already secure enough when the boat is going straight. Its the forces put on the transom when turning that make me concerned. Thoughts?
My other concern is that 150hp won't be enough motor to push the boat to 30 mph. If I can't reach that speed, I do not think the extra $2000 in motor and time for fabing would be worth it. Adding a third pontoon would be great but out of my price range, especially since I would need to get a new trailer. All comments appreciated, and thanks for looking!