Originally Posted by A.O. Razor

If that's true. How come Merc first rated the 525efi @ 500 prop ho, and the later, when they introduced the 600 sci and later models, the 525 was rated @ 525 hp, and not specified if it was prop or crank hp. From what I can see, they changed it, after the 575sci went out. That was 550 @ prop. I talked to a merc dealer about this a little while ago, and he said it was on the flywheel for both merc racing and mecruiser these days.

Another reason, I think why merc racing would not rate prop hp, is that a 525 with a ssm 6 would have a different prop hp than a bravo setup. So it does make sense, so rate them at the crank. I have no confirmation on this, but it seems like a plausable idea.