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""...goosing up a 9.9 ..."

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DJPerson

New member
I have a 1998 BF9.9A Honda outboard. It has a 'full throttle limiter screw' that does not allow the throttle butterfly valve to open completely. It is not mentioned in my SELOC Repair Manual.
1. Can it be removed/ discarded?
2. Will it become a 15hp at full throttle?
3. How is it adjusted.
The BF15A, 15hp outboard has the same bore and stroke and compression ratio as the BF9.9A Thanks in advance for any information
 
Goosing up a BF9.9A

*** This last weekend I took out the limiter screw. It has more power now that it can go full throttle. Looking at the intake manifold it is easy to see that it is designed for a bigger throttle bore, = bigger carburetor than the stock 9.9 comes with. To get it to a full 15 hp it would take a BF15A carb and perhaps control rods. This is beyond my budget unless I can find used parts. Also; the dealer told me the 15 has different cams. I don’t believe him. He said it had different jets, without saying it had a different carburetor entirely.
*
For now I am very happy to have the 2 or 3 extra hp I got from removing the throttle block screw. I hope in the future this information can help some one in the same situation.
 
It does have a different cam. Check the parts breakdowns for the same year motor.

He is also right on the jets and main nozzle. The markings on the carbs are different. So they probably are, but the carb without the jets, etc is not available. You have to purchase the whole thing...with all the parts.

Mike
 
Yep, different cams, different timing. If you're going to be adding more fuel, you have to ingest it, vaporize it and burn it correctly or you'll just foul your plugs and wash your cylinder walls.

You also need to consider that over speeding the engine to gain some "perceived" performance can cause engine failure.

If you get too far away from the 14.7:1 fuel air ratio by adding too much air to the intake, then you can cause a lean burn condition and fry that puppy pretty quick. Especially on a hot day.

The carburetor jetting and drilled orifices are only going to deliver a finite amount of fuel no matter how much the engine tries to suck it in. Opening the throttle plate wider and delivering more air does not necessarily equate to adding a matching quantity of fuel to maintain a proper mixture for worry free combustion.

But, your results may vary. If you leave it the way you have it, you might want to check your spark plug condition frequently at first to see how the burn is going. If they start looking ash colored or white at the tips, I'd put the limiter back. Good luck.
 
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