Can anyone tell me what the Differences are between a Mercury racing 502 in blue and a 502 Mag black ? Crank , rods , pistons , heads ??? Mechanic at the marina said to just bolt a whipple supercharger on the 502 mag . Another mechanic says it wont hold together and I would need a blue motor from mercury racing .

Don't know on the blue and black for the 502, but I do know a few of my friends that have whippled their 502mags with no problems. I think I've heard you have a better crank in the 502 as opposed to the 496 HO, so the 502 is suppose to be a better candidate for charging.

tom

Short blocks are the same from a Black 502 mag to a Blue 500Hp/EFI and I believe the only difference is the Heads and Cam. But, dont forget the fact that blue paint is what makes the horsepower

The HP 500 has a much better exhaust as well. The bigger blue motors have blueprinted and balanced lower ends but the HP 500 does not to my knowledge.

You can whipple a 502 Mag, but you should have inconel valves and good strong head gaskets. The same goes for the HP 500. Keep the boost at 4# or so and the motor will do well IF you keep the a/f ratio right and run premium fuel

My understanding, Blue motors are done by hand by Merc Racing division where as the black are production motors from Mercruiser / General Motors. The Blue paint is not worth much in the HP department, far as I know, but looks good. Basic diff is the Blue do have better parts.

Are you kidding me? All this time I thought it was the blue paint that added the horsepower!!!

Your Mech is right. Boost....

The 502 Mags handle the Superchargers just fine. I run mine at conservative boost (3-4lbs). I run my boat hard and the only problem I had earlier this year was a blown intake gasket. The boat is a 97 and has 360 hrs on it now (The Superchargers have been on it since it was new). So not bad for only needing an intake gasket at about the 240hr mark. My other engine has been trouble free (knock on wood).

I'm leaning towards a whipple setup on my current motor , after seeing the replies . Does anyone know if there are any clearance issues with the pulleys and the bulkhead on the 27 ?
I found another motor but it is not a marine engine , it's a 572 BB chevy crate motor for $ 4000.00 only seen 1200 miles in a street rod . Supposedly 650 hp with a single carb . I don't know if this would work in a boat . Not sure what changes it would require for marine use ?

I think car motors are clearenced for a warm block w warm water flowing through it. Most marine blocks have a cold block clearence w cold water running through it. Meaning A car motor might have too tight of clearences. i could be wrong. There is room for a 250 blower on a 27.. Just had to cut small clearence in the bulk head. ( not all the way to the back of the back seat)