Hi all
im running a 5.7 Mercruiser v8 in my 22ft speed boat, power is around 250hp and she hits 60mph gps with a 23p prop and Yamaha leg ratio about 1.8
I’m on a budget and been offered a cheap 400hp v8 from a car.
I didn’t fancy pulling cam and all the stuff that goes with it, so I’m wondering if a road cam (not sure of the cam spec, but I know it’s not a truck or Rev application) would work ok without any water being pulled back with the stock Mercruiser manifolds and risers.
Thanks for your time and input in advance

Might, or might not. You need to know cam specs, or it will be a blind guess at best.

What Underpsi68 said ... you really need to know more detail. Also some exhaust setups will prevent reversion better than others. As a VERY general rule, lobe separation on a lot of cams chosen with preventing reversion in mind tend to be 112 degrees or more ... BUT there really are more details to be considered. It shouldn't be too hard to get cam specs unless they are custom grinds and paperwork is lost ... good luck!

This never ends well...
What is wrong with the original 350? Why are you replacing it with an unknown asset?

Chances are if its a hot rod engine out of a car, which almost all SBC 400's were, it will revert water.

unless i read it wrong the op said a 400hp engine but did not state what cu in the engine is.

It’s still a 5.7 350 ci V8 with 400bhp
has modified heads, cam, intake, Holley carb etc.

3/4 road cam maybe ?

Pssst: I'm just playin' OP. Not ennough info. We need cam part # and/or specs . What size and who's V8. That was not even mentioned, so figured I'd add a laugh or two.

A 5.7l with large enough cam to make 400hp is going to revert h20 with stock merc exhaust.