HP ratings at prop vs flywheel

[Lion hunter]

Another post on here got me thinking about hp ratings and hull ratings. Being that HP used to be measured at the flywheel, does that change the hull rating of an older boat. If my old hull is rated for 100hp (which is about 80-90 today) and I put a new 100hp motor on it, am I over the rating?

 

[tashasdaddy]

Re: HP ratings at prop vs flywheel

legally no. but consider the weight of the motor itself compare to the original.

 

[Cricket Too]

Re: HP ratings at prop vs flywheel

I'm pretty sure the difference between flywheel rated HP and prop rated HP, was like 5% at most, probably closer to 3 or 4%. So your old 100 rated at the flywheel would have really only been like 95-97HP at the prop....it wasn't all that drastic.

In all honesty the HP sticker on the cover of an engine is kind of BS in a lot of cases. How much difference can there be between a 115 and a 140, or a 150 and 175, 200 and a 225....pretty much Zero.

They just rate the HP at a different RPM and put a different sticker on it, at least that's the way it was explained to me along time ago....could be wrong or slightly innacurate.

I think the hull ratings are BS half the time too. I had an old 16' CC that somehow was rated by the USCG for 6 people and a 150hp motor. I don't know what jackass rated that one up.

If you put a new 100hp on your boat, it will probably be lighter than an older 100hp anyway.