Offshoreonly.com - Mercruiser hp rating correction factors

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A.O. Razor

08-19-2010 04:17 PM

I agree with onesickpantera. I recall when the 525 first came out, it was rated at 500 hp on the prop, in the same way the HP500 was rated at 470 hp. Later on, Merc changed it to 525, and did not mention if it was on the crank. I think this change happened when they replaced the 575sci with the 600 sci. I even think I have an old brochure where the 600sc and 525sc are rated as 550 hp and 490 hp prop. I will see if I can make a good scan of it, if I can find it.

onesickpantera

08-19-2010 05:12 PM

I agree it gets confusing! Plus, back in the day I think the non-mag 454s were rated both ways(310 and 330).

I believe the 525s should be called 550s, but Merc was afraid if they did that no one would buy the 600s. :eek: :D

fireguy

08-19-2010 05:20 PM

Quote:

Originally Posted by onesickpantera (Post 3186431)

That's probably a very good point. That would make the point of diminshing marginal returns look very favorably towards the 525.

neva satisfied

08-19-2010 06:05 PM

Quote:

Originally Posted by onesickpantera (Post 3186152)

I respectfully disagree as the 502 Mag was rated at 415hp at the prop and the HP500 were 500 at the crank(470 at the prop)

Mercruiser sterndrive examples:

502 Mag - 415hp at the prop
454 Mag - 385hp at the prop
350 Mag - 300hp at the prop

Merc Racing examples:

HP500 - 500 at the crank
HP575 - 575 at the crank
Scorpion 377 - 377 at the crank
HP525 - 525 at the crank

I think the confusion comes into play because the 525 is always WAY more than 525 hp.

Either way I was curious as to if Merc used SAE.

Thanks

If this is the case...what are the 496 Mags and H.O.s rated for at the crank?

onesickpantera

08-19-2010 07:01 PM

Quote:

Originally Posted by neva satisfied (Post 3186463)

If this is the case...what are the 496 Mags and H.O.s rated for at the crank?

I would assume +30hp since that is what Merc deducts. I do know that the "black" motors are usually over rated a bit and crank dyno a little higher than the pshp rating.

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