NEW BF9.9, 13.2 HP? Honda gurus please read...

[dann03]

This is copied from another forum....




The old (blue & white) Honda BF75 and BF100 were essentially the same engine with the aforementioned changes in cam and carb. The 'new' Honda BF9.9 and BF15 are an entirely different design. Furthermore, the old BF100 is still made and now marketed as the BF8. Prior to about 1988 the horsepower was designated by the FLYWHEEL horsepower, after that, it was designated by available horsepower at the PROP; thus the old BF100 really put about 8HP at the prop.

There is no economical or practical way I know of to hop-up the old BF100 (at least not in the way of parts swaps). The new BF9.9 actually puts out 13.2HP (at the prop). It is limited to 9.9HP (for legal reasons on small inland lakes requiring "less than 10HP") by a stop screw in the throttle system. Removal of this screw gives you 13.2 HP engine with a power curve that puts the max torque a little lower in the power band as compared to the BF15.

I have a new 2007 BF9.9. Is this the case with my engine? Is there even any truth to it? I'd love the benefit of the extra 3.3 HP.. Thanks for reading.... Dan

 

[steelespike]

Re: NEW BF9.9, 13.2 HP? Honda gurus please read...

My info indicates The new 9.9 and 8 are the same displacement about 13 cubes and the same weight leads me to believe they are the same motor.The BF15 is a different design at about 21 cubes it is sold as a 15 or 20 hp.Horsepower at the prop would be something closer to 3 to 5% less than the flywheel.My guess is it is not as simple as a screw.It certainly could develope 13 hp but I'm inclined to think that the ratings are arrived at using ideal caming,carburation and timing to suit the application.Simply limiting the output with a stop would leave you with a motor operating below it most efficient design.