Looking at a boat that has a 502 in it (gen 6). He said the base engine is 450 HP. he said he got it through GM's performance auto division. Then did stuff to the engine. Did everything to HP 500 specs but the cam and left it at a lower lift. Here is what he did: Gil ss dry exhaust, inconel exhaust valves, roller lifters, Crower roller rockers, MSD ignition, and race motor mounts.

Any feedback regarding this. Is this a standard marine engine. Engine was done by ensposota (Spelling???) in MI (said they do a lot of marine racing, etc.). Thanks

The 502HO from Chevy High Performance is not all that different than a 502Mag marine engine. A lot of people here on the board have stated that the engines GM produces for the marine market are built to tighter and slightly different tolerances. There are a lot of guys running these "Hot Rod" engines in boats with good success though.

The heads on an HP500 have ø2.25" intake valves vs. the ø2.19" found in the 502HO and 502Mag. The exhaust valves in all 3 engines are the same size, 1.88", with the HP500 having better quality inconel.

As for the cams in each of the 3 engines, they are quite different. A 502Mag marine engine has a vary mild .480"/.480" lift 224°/224° duration 115°LSA cam. The 502HO also has a mild .510"/.540" lift 211°/230° duration 112°LSA cam. The HP500 had 2 versions, one for a carb and one for EFI; the cams are custom ground from Crane and have like 0.600" lift 230° duration.

My guess is that this engine producess a little more power than a stock marine 502Mag, but not as much as an HP500.