Prop rated vs. powerhead rated HP?

[groundloop]

It's winter, too cold to go boating, and I'm getting bored........ In discussions about the power difference at the prop between powerhead rated engines and prop rated engines I've always heard that there was about a 10% difference. To my pea sized brain that sounds like a lot, on a 200 HP engine they're talking about losing 20 HP to the gearcase. Anybody have any data indicating how much power is really lost in a gearcase?

[rkmirage]

10% is pretty close.

[Dave Strong]

Merc had 225,200,175,and 150HP when hp was power head rated. When they went propshaft hp had 200,175,150 and 135hp.

Dave

[Forkin' Crazy]

7% is what Chuck Goodman said.

[HStream1]

It depends on what gear ratio the lower has also. So 7 to 10% is a good parameter.