I would think cooling system would be important as closed keeps block temps more stable.

RUFSTR had one... They had talked to GM about marine use. it's Not even close. Id be surprised if it gets on plane without 2 speed trans or a ton of prop slip. Its also not even remotely tuned for it..so youre back to running dry exhaust with an 02 sensor and leaving it in closed loop (bad plan) or having it properly tuned. Too much compression for a pump gas marine engine as well. Knock sensors will be going nuts, and knock is very hard to quantify in a boat. The whole thing is a bad plan in a boat.
Still a deeply impressive engine though.

nice experience backed comments! The fact that it MAY not last years and years does not surprise me
but what DOES impress me is the fact you say it might not even get on plane even with 1000 hp!!!
marine engines seems to really need a complete different recipe then street cars!

Johnny,

Rod angle aside, wouldn't a cam swap, properly clearanced bearings and marine appropriate exhaust pretty much solve the issue?

Thanks. Brad.

I would rather have a boat engine in a boat.

Piston to wall clearance, bearing clearance, ring gap, compression ratio, cam, efi mapping, the potential list goes on and on. By the time you're done you'd been better off starting from scratch.

Johnny,

Gotcha. I guess I didn't realize the list of differences was so extensive. I knew about bearing clearances and cam (and obviously the ECM tune along with it), but I didn't realize piston clearances and ring gap would be all that different. I guess that's why someone else is rebuilding my 496, huh?

Carry on.

Thanks. Brad.

Thye might be fine, they might not. 1000hp makes a lot of heat, Im sure there's a decent amount of clearance. BUT. 1000hp with 5+ gears (and coasting) makes way, way, way less heat than a boat that's essentially in 4th gear going up hill all day. You also have to add clearance for cold water marine application and the possibility of no stat. You can run a much tighter piston to wall if you warm the block up too.
It comes down to application. Somebody will bolt this in a 22 donzi or something else that is small and will basically be uncontrolable and get away with it. Anything that could handle sustained WOT pulls and you'll turn it into junk.
Perfect example. GM rates the Gen6 502 block at 700hp. 700SCIs live at wot all day. I have a Stage 4 (850ish hp) 700 in my shop right now out of a 42 fountain that had a massive cylinder wall failure. It would have been fine in a smaller lighter boat. a 42 Fountain with M6 drives? Nah. Happily, we didnt build it lol.

Johnny,

If you HAD built it, it would have been right and wouldn't have failed.

Thanks. Brad.

I think it would work and perform great.

Not sure how long it would last though.

6800rpm redline would let you run a pretty low pitch prop that should work for planing off.

My first concern would be if the valvetrain could live, then if there is enough bearing clearance. Pump gas could be questionable too.

There’s been a couple boats with 1000hp NA big blocks that ran hard. I forgot the screen names, one had a light 41’ Apache that ran 110+ and the other a skater 32B that ran 160mph.