Horse power Rating's

[ross_larter]

Hi,<br /><br />I have been told that a 1996 60hp mercury has the same horsepower as a 1981 70hp mercury because they change were the horse power is measured.<br /><br />Is this true? Anybody got any more info on this.<br /><br />Cheers<br />Ross

 

[FlyBoyMark]

Re: Horse power Rating's

Pretty much.....Mercury had a 50 HP 4 cylinder, then derated it to 40 HP when they started prop rating it. The old 40 HP 2 cylinder they used to make that was also their first looper to hit the market several years ago was also derated to 35 HP untill about 1988 when it was discontinued.

 

[chrysleroutboard]

Re: Horse power Rating's

Hi, Does anyone know when all manufacturers (Mercury, Johnson, Chrysler, etc.) started rated Hp by prop rating. I have 1972 85 Hp Chrysler motor (I think flywheel rating). what is it equivalent Hp in term of prop rating? Is there any rule of thump to convert flywheel rating to prop rating? 10,15 or 20 % reduction?

 

[FlyBoyMark]

Re: Horse power Rating's

Percentage is not set in stone....The efficentcy of the lower units gears and bearings have alot to do with it. Drag of the lower gear train, large versus small, ect. Most small engines were about 5 Hp up to about 40 hp and above that; 7 to 10 hp; and the biggies, up to 15 to 20 HP.