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Honda BF 9.9 4stroke 1998 (15hp)

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Pooey

New member
Hey Guys, i have been told that the 9.9hp is basically the same as the 15hp, with the only difference is in the throttle somehow. Does anyone have any experience on this subject ?
Cheers
Pooey
 
Pooey, pre-2000 BF9.9 and BF15 are the same exact block/displacement. The 9.9's max hp rpm range is 4500-5500 and the 15hp's is 5000-6200 rpm. So one or more things are different so that the 15 makes more rpm and power. I've been trying to find out the same info as you so I can possibly? upgrade my 96' 9.9hp. I've heard that the 9.9 has a throttle stop that the 15 doesn't and that the 15 is either running the same carburator with a larger jet or just a different/bigger carburator. But an additional difference I've heard that I haven't been able to confirm yet is that the 15hp has a different (more aggressive) camshaft in it. If it's just the throttle stop and carb, I'll consider it but if the camshaft thing is true then it doesn't seem worth it. Hopefully somebody on here can clear this up.

CM
 
Thanks CM
The guy i bought it off said just that. All you need to do is adjust or remove the throttle stop to gain more revs. This might just be an urban myth for the hopefulls out there. I'll see if i can find any internal differences such as the camshaft.
Cheers
Pooey
 
Hey guys,

The head is the same, the valves are the same, the camshaft is different and, I suspect, the timing is a tad different as well if you were to "upgrade" the cam. I'm guessing one to two cogs advanced.

They definitely are "pouring more coal" to the 15 with a larger main and slow jet set. 108 vs 102 stock main and a 52 vs 48 slow jet set with different main nozzles as well.

So, the old "find the throttle stop and eliminate it" is a pipe dream for sure.

But, the old "peel off the 9.9 and replace with 15 decal" still works!
 
Love your work jgmo. I suspected there would be more required than just the throttle stop. For all the work required, i don't think the power increase would be that exceptional. Much easier to buy the right size in the first place.

Anyway, the old girl can stay happy at 9.9 and i'll dress her up with some new paint and decals to make her feel new again.

Happy Hondering
Cheers
Pooey
 
Thanks Jgmo. Confirms the suspicions/facts I had found up to this point. All those factors considered, if I really wanted/needed the extra power I'd just sell the 9.9 and get a 15 instead. I really don't need it though. My 9.9 is certainly adequate enough. I like your thinking though. Except I'd maybe have fun and put an "8" decal on it and just say I've got a motor that over performs!

CM
 
And, you know that it's already been re-decal-ed once anyway. It was the 10 horse until several "impoundment" and river authorities around the country thought it wise to limit outboard power to UNDER 10 hp. That was the birth of the 9.9 "designation".
 
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