Ok you read the question.
I need an engine this weekend.
Are the tolerances OK for marine life. Cam seems ok, only 211/230 @ .050. I am not worried about warranty.
ANYONE DONE THIS?
THanks
JIM

I did a 502 crate short block when the Gen V motor first came out.. I ran it without tearing it down the first summer.. Tossed in a roller cam, heads, carb etc.. Ended up having some piston wall scoring. They say because of the cold water temps with the Merc 140* thermostat. If you need to get a motor.. it would work, but I would maybe put a little warmer stat in it.. then you have to be concerned about detonation, if things get too hot.. but at 160*, I think you would be ok..
One thing to note.. Gen 4 flywheels dont work on Gen V IV motors.. different balance..

Hope this helps..
Dick

I wouldn't trust the clearances. I remmeber a post, as one example, of someone that toasted 2 of them. I thinkn most of the machine work on GM standard crate motors (not the high end stuff), short blocks and bare blocks, is done in Mexico. In an automotive application maybe it would run, in a boat applcation I'd go through it first.

Theres alot more strain on a marine application, I'm sure that a stock GM motor would not hold up well with the high RPM use. Just my 02.

There is not any difference in a 454 or 502 short block from a car to a boat. They both come from GM assembled. Merc does not buy short blocks from GM, tear them apart, change something, and reassemble them. I just finished rebuilding my 500 EFI's and they had GM bearings, rings, pistons, oil pump, etc. Even the head gaskets and intake gaskets were GM. Keep in mind, GM has better machine euipment than anybody except maybe Ford Etc.

The cams GM supplies, Merc does not use. The are mostly on 110 lobe centers that promotes reversion. You should by a crane or other cam on 112 or 114 lobe centers about 224/230 @.050 or slightly smaller. The GM Valves used are on all non HP motors. All HP motors have good valves. If using a roller cam, I would not use the GM springs. Most all HP motors use Comp 929 springs set @ 1.880. If you use a roller cam, the GM lifter can only handle so much lift. Cranes web site gives good detail on this and they make long travel lifters. I do not like the GM non adjustable rockers. They can be converted to roller rockers pretty easy.

I have seen people just buy a long block and run it and it works. I know a couple people who have run it for a few years without problems. I would not do that myself, but I would buy a long block & alter it as above.

Good Luck.

I'd just hammer in some brass freeze plugs and run it.

I put one in my Donzi Criterion last year...

I love this engine, great value.

I didn't change anything.

I would buy another one in a second.

Jim

I don't know where you live, but there was a car dealer here in the Cleveland area that had a few left over 502's for sale. I asked about them and the counter person said someone ordered them, and never picked them up. They are selling cheap, probably less than you can get a 454 HO for, I can't remember the price. I know at least one of them was a 502ZZ motor.

I am land locked in Nebraska.
Do you happen to have the number of the dealer.

Dealer's name is Tim Lally Chevrolet. Biggest truck dealer in the area.
Number is 440-232-2000
Website is http://www.timlally.com
This was last year, but I am sure he still has those motors. Give them a call, you could save a bundle. Let me know if I can help out in any way.