TOPIC: Question about Horsepower rating motor/boat

Boats have the rated or recommended Hp rating on the CG tag.
My question is most motors back in the day, the Hp was rated off the flywheel not the prop.
So how was a boats rating rated?

I was told that Merc 500 is comparable to that of 45hp or less? because of how they rated these?

So whats an Merc 1500 Hp rating at the prop, anyone know? or know of basic calculation one cas guess-itimate? >: lol

Just curious...i read where one refered a 1150 to only producing around 95hp?

Matt, the 1500 will be the equivalent of 120HP by todays standards, a little more or a little less depending on the tune etc. Generally speaking they loose about 25 to 30 hp through the drive train, the non power ported 1150 is basically a 90. The power ported post 1984 1150 is the old 1400 and so on. If you have an old boat the ratings were done with the available engines at the time.

thanks, that helps me out a bit...and adds more the knowledge upstairs thank you.