old hp verse new hp rating

[mrpike1973]

just wondering what older motors actually have for horse power. i have a 15 hp 1978 evinrude and a 25 hp 1977 evinrude. if compared to a new 15 hp or 25 hp motors today. would they be less power or more or not a huge difference at all. just wondering if i put a old 15 hp motor on a new boat today rated for say 15 hp what would the difference be. saw this brought up on another post and well my little mind wonders.

[jentz]

Bout 10% less for older motors Old 15 HO now would be rated 13.5HP

[delcecchi]

Long ago, HP was rated at the power head. In about the mid to late 80's the rules were changed to rating at the prop shaft. Might have been other things too.

The 4 cylinder 50 merc became a 45, the 35 evinrude became a 30, and the 40 Merc (2 cylinder) became a 35.

So your 15 is less than 15 by today's standards.

[dan z]

Buddy of mine had a 35hp evinrude 80's on his duck boat and went south this past fall. Got lucky with a 2000 20hp merc that someone had laying in the basement. Well long story short that 20hp merc does really well to say the least. New motors make a world of difference.

[mrpike1973]

thanks that answers my curious little mind thanks again