Re: Opinions on a project..
Re: Opinions on a project..
I already have the 355 sitting in my garage, was meant for a 69 c10 i got rid of, and mounts i wouldnt think would be too hard, but i didnt know id have to re gear the outdrive and re balance the boat. Anyone have any references on how to do something like that? Also, so in theory could a boat handle that power? I understand the drive can but, i guess i am asking what i forgot or didnt know to take into account, I just assume i could swap almost anything in and go like my old trucks?
You can, but as you mention you may exceed the power rating for the boat. The coast guard formula for that is basically lengthXwidth for smaller boats but for a 19 footer it will depend on the height of the transom and whether you have power steering. Horsepower up to the max for the drive (in the 300-400 hp range) wouldn't be insane for a boat that size, but you will pay for the privilege in insurance costs.
Plus if you upgrade the engine for reasons other than "it's broken" then get in an accident that'll count against you... the other lawyer will argue your hopped-up boat is a speed demon, etc.
FYI, boat performance depends far more on torque than overall HP or rpm, so your 355 won't significantly outperform a regular stock 350, even if you add on accessories that would increase HP in a truck or car. There's a noticeable difference between 305 and 350 power, but the next step that you "feel" is a 454.
Re-gearing the outdrive is needed because A) Boats don't have transmissions and B) Your prop is sized largely based on torque. The fixed gearing on the drive is designed to transform the engine torque into the minimum needed to get moving while preserving the largest RPM range posssible. For most engines in the four cylinder range the drive is at about a 1.3:1 ratio, for a V-8 it'll be about 1.5:1. If you don't re-gear you lose much of the advantage of the bigger engine, and worse you may be outside the "good" performance envelope for the prop, resulting in stuff like not being able to get on plane in a reasonable amount of time.
To rebalance the boat is simple. Build the boat out according to your plan, then put it in the water. At the dock, note whether it floats on its lines (evenly in the water) or is stern or forward heavy. Move weight forward or back (in significant amounts) to balance it. Ideally you should do this with math before you build it, since you may not be able to move enough weight around to make the difference you need.
If you have specific questions about the drive, gearing, and what you need to do, I'd post them in the Sterndrives section here, and keep your main project thread in the restoration section.
Keep posting and good luck,
Erik
