merc 500hp is that at prop or flywheel
 

When you see the merc 500hp engines are those prop shaft or fly wheel and how much hp do you loose through the drive?

thamks for any info guys
josh

flywheel, 470 at the prop.

Up until very recently, the general consensus from virtually everyone around here was that it was at the prop. If you do a search you will find lots of evidance that all the mercury racing numbers are at the prop, and normal Merc stuff is at the crank.

Recently, I've seen a few people say the opposite. Personally, just knowing what the HP500 and 525 have in them, I can't imagine how it could be at the crank. For that motor to make 470 HP with that cam would be absolutley pathetic. They'd have to be running bearings made of sandpaper, or adding intake gaskets with 1 inch holes.

500 EFI was 470 at the prop but merc racing changed the way they did ratings when they started selling complete motors and drive packages. The 525 is at the prop call merc racing and they can confim this for anyone

470hp at the prop. They are all underrated tho.

I know what the dyno said the 500 made 506hp put a 525 cam in it and 528hp , But that is a 525 cam in an iron head motor. Just my $0.02

The 500 is rated at the flywheel and 470 at the prop. The 525 is at the flywheel and 500 at the prop. Everybody says they are underrated, but keep in mind Merc uses an SAE hp correction factor and most aftermarket dynos use a standard corretion factor. Therefore Merc blue motors generally dyno higher than rated when run on an independent dyno. I have a propshaft dyno. My experience has been approximately 10-11% loss through a Bravo drive, and they make quite a bit less than rated when measured at the prop. I have not had the opportunity to dyno a stock 525 to see what it really makes at the prop. I did have an opportunity to dyno a 496ho. It made 387 at the prop. Removed the engine and bolted it onto the dyno and got 431 at the flywheel. I also dyno'd a stock 500 EFI at just over 500 at the flywheel.