blown1500

Hello Guys,
GETT"N BYE, Mercruiser gets theirs from GM. The Chevy crate motors are NOT marine engines. If you buy one, you need to have someone blueprint it for you -GM does a mediocre job on this. I know many of you have used these with no problem, but I see a lot with problems the Mercruiser.s don't have.
Mercruiser does their own machine work and they are VERY good. They get all the numbers right-GM goes for a much larger spread in their acceptable ranges. Good machine and assembly work is what you pay Mercruiser for.

GETTINBYE

blown1500,

I most certainly agree with you when it comes to the high performance models. I do know they are disassembled and blueprinted to some degree as well as being run/broken in&tuned on the dyno before they leave Merc. & yes they do a great gob. I am a happy camper with my 500s.

I however do not believe that this is the case with all of the engines they put out such as the average 454 & 502 MPIs etc. Just don't think it would be cost effective because of the large amount they produce. The HP versions even come out of a different assembly plant.

Have not been to either place. Just my opinion as I have stated above.

Mark

dyno

Dudes!!!!the Thread is Deals on GM 502 short Blocks!!!!Blown1500 you seem to think we are all running Super Cat Light or some thing.....The stock 7.4's in my boat ran 400 hrs and it was beat to **** most of it ....with out fail the GM 502's are a much better piece to start with than the cast crap (that has served me well so far) Granted I would have them balanced locally but I can have that done for about $200 so thats $3900 a good deal from where I'm sitting....

Tom McCann

Mercury uses none of its own parts.exept ignition when assembling its engines. All parts comes from outside vendors. Hp engines use the folowing parts suppliers. Gm for the block, J&E for pistons, Manely For the rods, Crane for the valve train, Dart for the intake, holley supplies carburation, Heads, crank and block come from the Gm hp catalog. The heads are rectangle port machined by mercury ,also crank work is done by mercury. Your best bet on getting a block and parts is buy through Summit catalog or other performance parts catalog and have your machine shop do the machine work on the crank and heads and assemble the engine your self or your machine shop. Check around your area for a reputable machine shop. This would be the most economical way of getting an engine thats mercury quality. For example a camshaft bought through mercury for a common Hp500 would cost around $1000. Buy that same Camshaft from Crane and its costs around $300. Hope I didnt confuse anyone, if you need more help let me know.

dyno

Tom now thats good advice!!!!Thank you!

dyno

Wow and thats your first post......Give us a little of your back ground will ya?

rpm

Tom is correct - The HP 500's use Manley H-Beam rods and they have Mercury Racing etched into the side of them. Since the discontinuation of the 502 by GM, all 502/525 engines are hand built in Fond du Lac.

Rod

Mr Gadgets

Dyno,
Years ago I picked up one of the first 502 Gen V short blocks released from GM. It wasnt suppose to come with a cam, but there was one in it when I received it. It was a hydraulic flat tappet cam, same one that Merc was using in the new 502 of that period. I put some iron Merlin heads and roller cam in it. Made good power, but the cylinder walls ened up scoring.. we assumed to little PtoW clearance. After that did a whole bunch to it.. ended up with 690hp when I gave up on it.. I changed the pistons and rods, but the rotating assembly would have been just fine. In my opinion, I would do it again but I would measure and adjust the clearances, mainly PtoW and rings and such. But you are right it is a nice piece to start with.. Check around you can get some decent prices on them from some regular Chevy dealers. I could check my source if you are seriously looking into it..

Dick

Pure Energy

rjcardinal,

when you say you

"I believe the 502 partial enigine and all GM 502 crate engines shortblocks are the same as they sell to Merc. The only time the clearances are modified by Merc are in the hand built HP series"

And

"probably the 525 EFI shortblocks come straight from GM and are the same as every other 502 shortblocks they sell."

And

"To my knowledge the GM Partial 502 listed above has the same shortblock with the same parts and clearances as every 502 Mag, HP500, and 500EFI Merc has ever sold. I havent researced the 525EFI yet but its probably the same also."


The key words here are "I believe" and "probably", and "To my knowledge". It sounds like you are guessing. Are you stating facts, and if so where does your info come from? I have been told by numerous professionals and DIY people that there is a diff. between a marine motor and a street motor.

Tom McCann

There is a diff between a marine motor and a street motor., PRICE. As far as the tolerances go on the crank and bore of the cylinder wall thats up to the machine shop doing the work. There is no mystery in building a strong marine motor. Anyone who builds marine motors for a living wants you to think this, or else they would lose business. When building a motor choose parts that are allready proven. I allready gave you a list of the manufactures that supply parts for the Merc Hp motors, get on the phone and call these manufactures they will be more than happy to sell you the same parts they supply merc with. Any questions let me know. Have fun