Logo
FULL SITE MENU

1997 bf9.9hp to 15 conversion

S

shopskies

New member
I've got a 97 9.9 that I'm looking to convert to a 15. Aside from jetting in the carb is there anything else that needs to be changed on this motor for the swap. I've done a 2 stroke conversion for more hp but not a 4 stroke yet. Is it the same cam and timing, or is the valve clearnace greater on the 15 to account for more air? Anything helps all I've got is the 2 parts diagrams and I'm comparing
 
Interesting question. I don't have your answer(s).

But, like you, looking at part numbers, the camshafts don't match....the spark plugs are different....

the main emulsion nozzle is different and the 9.9 has a #48 low speed jet while the 15 has a #52. Both of which aren't available for either outboard

Also, you wouldn't increase valve clearances for "more air". If anything, that would be reduced. But I wouldn't recommend doing that unless you have the specifications. I don't have that information.

The heads, valves, rockers and springs are the same for both engines so....they're close for sure.

Not to rain on your parade but I don't think trying this will work. The cams are probably ground slightly different for one to handle the increased fuel that the larger jets would provide. And, I'm guessing that the ignition timing "map" for spark advance in the CDI will be slightly different as well.

They haven't offered replacement CDI for so long they aren't even listed in the parts pages to compare numbers.

You could have everything lined up mechanically but, if you don't fire the plugs on time it will defeat the process of doing what you're trying to do.
ie: making more power when it's needed most.

If you could get another cam, the carb jets and a CDI you might be in business but the only thing available new is the spark plugs.

Good luck though.
 
Yep, you just might be successful with all the right parts.

I didn't list the pulsar coil before but, if you swap out the CDI, it might be prudent to swap that too since those work together for advancing the ignition timing. Hard to say because no part numbers provided for obsolete pieces.

Good luck.
 
If you go to boats.net select the part in question and scroll down to the bottom you will find a list of engines that share the same part.
 
An important point that is often overlooked is the carb throat/intake manifold. Only so much air will pass through the carb throat. If you simply use a bigger jet, (more fuel), with the same throat diameter, it will run rich.
This has been tried many times with the 2-stroke 9.9 to 15 conversion. Measure the throat of your current carb, then compare that to a genuine non messed with 15. If the 15 has a larger diameter, simply rejetting your 9.9 won’t work.
 
Back
Top