Just curious where I can find actual HP rating on the 502, Ive always thought my 93 502 carb was 415, after talking to some people I hear it was 390hp, anyone know for sure? also what are 94 502 fuel injected motors rated at??

thanks

Early 502's (Mark IV and Gen V's) were rated at 425 at the flywheel and 390 at the prop (carb). This number grew in the early 90's with the advent of EFI.

The EFI 502 went up to 415 at the prop and the 454 Mag went to 385 hp at the prop

thank you

My knowledge and information tells me that these engines are all Mercruiser (black) engines not Mercury Racing (blue) engines and most of the time during this period Mercruiser unlike Mercury Racing has most of the time rated their engines only at the crankshaft. So as measured by many in the industry those horsepower numbers were what appeared at the crankshaft, not the propshaft.
Just for example the Merc 496HO (Mercruiser engine) rated at 425HP measures about 395HP at the propshaft and the HP525efi (Mercury Racing) engine is rated at 525HP and measures that at the propshaft and actually makes about 550-560HP at the crankshaft.
Reason I feel this is more accurate is I have never seen a Mercruiser stock 502MPI rated 415HP outperform a stock Mercruiser 496HO-425HP.
I know it makes owners of Mercruiser (black engines) feel better about their powerplants when they believe their engine is making that HP number at the prop, but the truth most of the time is that is the horsepower they are making at the crankshaft.

Good formula to remember when identifying horspower numbers on Mercury marine inboard engines:

Motor in black horsepower at the crank,
Motor in blue horsepower at the prop.

Best Regards,
Ray @ Raylar

that's it im painting all my stuff blue

Huh? Why would it? Its rated for less horsepower (at the crank or at the prop).

Great idea, that is the cheapest horsepower I have ever heard of. Mind if I do it too?

Powerquest is correct this is how they were rated.

From what I have seen all black engines are over-rated a touch and all blue engines under-rated a touch. Except the 525 which was under-rated by quite a bit. My guess is to keep the sales of the 600 up.

EFI Black engines are at the prop
Blue Engines are rated at the crank. However it seems the HP 525 is under rated.
http://brucebullockmarine.com/mercury/350-454-502.html
http://brucebullockmarine.com/mercury/500.html

I know that this horsepower rating information clarifications step on the capes of a lot of superman powerboaters but if you dyno a stock 502MPI at the prop you will see the real power at the prop. I believe Bob at full Throttle has done many such prop test power levels on his propshaft dyno and maybe he will be kind enough to reshare his findings.
Powerquest Baby, if it makes you fell better that a stock 502MPI makes 415 or 425hp at the prop have at it, I know what it really makes regardless of advertising or opinions here on OSO.

Best Regards,
Ray @ Raylar