Hi,im new to this jet boat game..I would like some advice..Im looking for a gig block chev...I found some marine and some street......whats the deal...can i use a street motor without tearing it down replacing gaskets and some other things I was told...or just buy a used marine 4 my first motor to blow up......lol thanks i run rivers and lakes on east coast no salt water..
As Kreg said the biggest difference is clearances. I would normally use bearing clearances close to .003" on a big block, additional piston to wall clearance, since the block temperatures run cooler in a boat, and the pistons are usually going to be hotter from being run harder. Since marine engines are typically run at double the RPM of a normal street engine (I run 80 MPH on the freeway at 2500 RPM), most engine builders would recommend forged pistons, rather than factory cast pistons. Also, for the same reason, higher rpm range, you would normally run a larger duration camshaft.
One other big point would be to make sure to use a marine oil pan, partially due to rpm range, but also all the bouncing around a boat does, it's important to keep oil around the oil pump pickup.
You can drop a used street engine in the boat, but chances are it won't last real long, whereas a properly built and installed engine should last a long time.
