Again, all technical issues aside, the ZZ 502 is specifically not warrantied for a marine engine.

Call those guys at Dyno-flo. Talk to Scott. They have 540's turn key, set up for marine use and a 1 year warranty advertised for 8999. I think I saw this in Powerboat magazine. The web site shows a different price, but I think the price has gone down.

I just got a pair of 582's from them. Great customer service, and they answer the phone after the transaction.

I'd buy one of these before I bought a crate motor from Chevy. They come with a warranty too.

http://www.1800runsnew.com/newgm.htm

I have heard that the .002-.003 extra clearance they run on the marine motors are because of the block running at a cooler temp and the pistons running at a higher temp because of more of a load. I took a ride in a 24 outlaw yesterday that had a zz502 crate motor, all he did was marinize the carb,swapped the oil pan with an 8qt,ordered a gen 6 oil cooler and filter assy because his old one was off a gen 4 and wouldn't bolt up, swapped his alternator (something about the one that came with it different wiring), swapped the flywheel, he even left the HEI dist that it came with (note to self raise hatch before starting) put a set of EMI thunder exhaust manifolds on it and whala ! Boat runs sweet. Total cost without exhaust $8000 P.S. he got the engine for dealer cost. Boat has approx 100 hrs with setup. He is looking into a procharger now.

Those look like steals.

There is a thread on here about a guy who had major issues with them......

If you need a 502 MPI - Leon @ Derreberry has a few brand new in the crate long blocks left. We just bought one for a boat on the river down here. Leon is a great guy. I've purchased a couple of the same marine long blocks and you can't beat them. Complete with valve covers, oil pan, timing cover, etc.... (and these are true marine engines - not something some jackass pulled apart and changed this and that and calls it a marine engine) Your intake and accesories and your off and running. A car engine is just that - a car engine.

Or not enough MONEY!

Greetings from a Marine and Race Mechanic since 1983.

I have been told from GM themselves that there is no difference in clearences etc. from automotive to marine.

and they are correct... the difference is that an awful lot of marine guys think that overcooling the motors is beneficial for some reason... hence the "cold" clearences don't appear to be correct. if the motors run at correct operating temp, then the factory gm clearences are corrrect... if you are using alternate piston materials and making other mods then those factors determine the clearencing for that combination. there is nothing magic about the marine application that requires compromise anything for that reason alone.

I ran my ZZ502/502 for 4 seasons. I left the ZZ502/502 cam in place, and kept the SS exhaust valves. The marine (Thunderbolt) ignition, starter, alt., etc. from my original 7.4 all bolted on to the ZZ502. The carb that came with the ZZ was marinized (Nickerson) and head gaskets were changed to MARINE type. 30 lb. bypass installed in the side and the center valve was removed. Hardin oil cooler used (good to 700 hp according to Hardin). The oil pan from the 7.4 was used on the ZZ.

If you run the ZZ502/502 you will need a bigger oil cooler. I used the oil lines from the 7.4.... I'd suggest larger ID lines because I did have oil temp issues with my ZZ. A bigger pan would be a good idea too.

The engine was run at, or close to WOT for 20-25 minutes at a time in local poker runs over the 4 years I had it in my 23 Nova. I never had any issues with the engine. It ran perfectly, always. Other than having had to figure out/correct the oil temp thing, I can honestly say I had no problems with the engine.

The engine was torn down at 140 hours. All the internals looked great. If I was looking to re-power and wanted 500 HP would I get another ZZ502 ?? Yep