I have a Shakespeare Shadow with a ford Essex V6 connected to PP jet drive.
What I would like to know and can’t send to find it anywhere in the www.
Can I run the engine with a sealed cooling system as it would of been run in a a car without drawing in raw water via a heat exchanger and then it being pumped out via the exhaust.
Plan is to fit a a reasonable size alloy cooling rad with oil cooler also both with cooling fans, create some more air vents for more air flow around the engine, the exhaust I have a pair of Capri 3 branch manifold these turned upside down still fit the engine and point the exhaust to the rear, just require extending and raising slightly to bring the outlets to a safe point so no back wash can enter along with some flappers. I don’t see why it shouldn’t work but would like a little advise from anyone who may have tried a similar conversion themselves or know of a similar set up.
Many thanks. Tim

Why bother ?? it's a lot of messing about for little or no return, you have the best cooling system available for free (what the boat is floating in !!) . if it was a good idea some or all the major engine manufacturers would be doing it.........

you would need to move a serious amount of air - so quite a few horsepower for a proper fan and some pretty big trunking - which ideally should not let water into the interior!

Given the pp drive already supplies cooling water to the engine and the exchanger is a sensible size - what possible advantage does air/radiator cooling bring? Even if rotted out marine manifolds are not that expensive.