thedonz

what is the difference in performance and reliability between the 500HP and the 502 carb engines?

which one is better to supercharge?

H2Xmark

the 500hp has the better inconel exhaust valves in the head, and the exhaust manifolds are a lot better also, so far supercharging my vote would be the 500, if it's a 500hp carb they had some valvespring problems so if you get one of those early engines and you have around 200 hours on it upgrade the springs on it

CAP071

How about the 500 EFI ? stock running

H2Xmark

I would love to have a pair of 500efi's in my boat, great all around engine, the 500efi has the better valve springs that is the updated spring for a older 500hp carb engine

impulsive

I think there is no comparison with the 500efi. It's more a question of money in my opinion.

Dean Ferry

Fever Mike,
Do you know what the year was of the HP500 with the "Good" valve springs? I guess the ? is what year was your motor?
Thanks,
Dean

ActiveFun

But isn't the question comparing the HP500 and the 502?, not the HP500 EFI vs. the carb HP500? Or is that the same thing?? If it is.. Sorry for the ignorance

mcollinstn

Not sure which motors thedonz wants us to compare.

502Mag Carb MkIV thru 1991,
502Mag Carb Gen5 thru 1996,
502Mag EFI Gen6 thru present,
502 Horizon

HP500 Carb (blue motor)
500EFI (blue motor)

thedonz

thanks for your help guys, I guess what I am trying to understand is the difference between these engines identified by mcollinstn..basic difference between the hp500 and the 502 series......cubic inches, true horsepower, age, reliability...the reason I am asking is because I am shopping for a boat and leaning towards a Gun. basic engine configs appear to be those mentioned above, if I find a zul, chief, hawk, KE, etc. then better still.. ...I would like to start with a basic entry level setup and perhaps upgrade once I really know what I want as far as power...thanks for the input

mcollinstn

All Merc 502's come from the factory (GM) with forged crank, 7/16 rods, forged JE pistons, 4 bolt caps, iron rect port GM heads with 2.19/1.88 valves (3/8 stems).

Carbed 502 Magnums came with a cam with around 224/[email protected]" and .510 lift on 115 degree center (or thereabouts).

The BLUE motors, HP500, 500EFI, come with crane roller rockers, crane lifters, and crane cam (228/236 .570/.590 on 112 or thereabouts).

Black 502 carb motors come with aluminum GM hi rise dual plane intake and Rochester or Weber carb. Blue carb motors come with Dart sigle plane and Holley 800's.

500EFI comes with inconel exhausts, I believe.

That's a rough rundown. Black 502's are from 390hp to 415hp. Blue 502's are from 470 to 525hp.