502MAG EFI motor overhaul
 

I am in the process of overhauling my 2000 502MAG and question the parts that should be used. Should a guy stick will all Merc parts and gaskets or will aftermarket "car" parts do the job? I do not want to cut any corners and am willing to spend a few extra bucks to get the best for the $$. If aftermarket is OK what brands of say rod and main breaings and piston rings should I look at? How about gaskets brands? And head gaskets.....I see alot of discussion and Cometic Head Gaskets...are these the ones to use?
Does any one have a list of part numbers for these aftermarket part for this engine...my local parts store guys want to run the other way when I start to talk about boat parts.
Thanks,
Mike

Cometic or Felpro head gaskets. Use the Marine versions.

All other gaskets, I like Felpro. Do not use standard automotive anything. Would you buy your car parts from a boat dealer?????

Summit Racing and Jegs carry what you need.

Use marine head gaskets, they have stainless steel for corrosion issues. There is no difference between marine and automotive for rings, bearings, intake gaskets, exhaust gaskets, rear main seal, pan gasket, valve cover gaskets, valve springs, lifters, keepers, retainers, rocker arms, push rods etc. Just use good parts. There is no sense going with Merc for that stuff use Jegs or Summit. Go back with brass freeze plugs. Setup on the clearances is important however. Use a machine shop familiar with marine applications.

Agreed, Cometic for head gaskets though!!!

Beware that the exhaust valves are different, they're 2 piece partly stainless ... and chrome steel, I think.

Btw, does anyone have experience in converting crate 502 HO's for marine use? Ackording to 'a book' the Mercruiser's (and possibly others as well) are built on GM production units right off the band with some minor mod's like camshaft, valves, head gaskets ...

Also, I have seen 'Marine' 502 base engines beeing advertised but I have not yet been confirmed that they are fully compatible with stock 502 EFI's / MPI's. My main concerns is around cam and valve timing ...

Hey mpottorff, I was wondering if you could help me out with the part numbers off the main wireing harness and your Mercrusier engine block serial number Thanks

I'm doing mine right now. The short block was a GM replacment piece and had the ZZ502 cam. Upgrading that to a 731 or similar custom grind. You'll want to see what valves are in yours and go from there. Inconnel on the exhaust side for sure.

The only difference between the HO and ZZ short block should be the cam. The HO base engine comes with the iron 934 heads, probably superseeding the 'Gen V' 088's.
When checking on the 934's they're are specified as 'Marine' on MorTec, I wonder what that means ...?

DMAX
Let me know what and where the numbers are and I'll help you out.
Mike

I'm not sure where the harness #s are but the engine serial # is on the top of the black box where all the plugs,computer etc are. Thanks John.