Hey Frank, fuel starving at high rpm.

[tjello327]

Hello forum,
I have a 1986 125hp force outboard. Finally took out for a test run for outdrive problems. Worked great, but at high rpm the engine sounds like it is starving for fuel. New fuel pump, fresh gas, lines are in good shape, carbs rebuilt. I did reset the floats on the conservitive side becuase I thought it was flooding. My question is what is the correct float rise & float drop. Which one of these would cause fuel starving? My total range of movement of the float is pretty small where it is set now. Lots of room for more float drop, a little more room for more float rise. Thanks!

 

[john from md]

Re: Hey Frank, fuel starving at high rpm.

The book says 13/32 from the carb body to the float top.

I found this to be too low for my 85hp and bent the tang so that I got more fuel in the bowl. Unfortunately I did not record the number.

John

 

[tjello327]

Re: Hey Frank, fuel starving at high rpm.

Thanks John,
I set my float for more float drop (about 13/16") and float rise to where the float is about level. The range of motion has been increased by doing this. I understand float rise shuts off the needle later when set higher, but still not sure what float drop does for you when it is set lower. does anyone know?

Thanks!

 

[Frank Acampora]

Re: Hey Frank, fuel starving at high rpm.

If there is not enough float drop, the needles will not open fully and the fuel level in the carb bowls will be too low. This will result in lean running on all cylinders and loss of power at full throttle where the engine really sucks fuel. It will probably not cause problems at partial throttle where the engine does not need nearly as much fuel and the reduced fuel flow will be able to keep up with the engine's needs.

 

[tjello327]

Re: Hey Frank, fuel starving at high rpm.

Thanks Frank, I knew you would have the answer that I was needing.
I dropped the float a little and am going to try it Friday. I'm sure that will be the problem. It runs too good in all other rmp ranges, starts right up, idles smooth, planes quick, it just is lacking the wide open rpm.

Thanks again, I'll keep you posted.

 

[tjello327]

Re: Hey Frank, fuel starving at high rpm.

Well tested out on the lake and seems alot better as far as the fuel starving issues but still not getting as much top speed as I think it can and sucking the fuel down pretty quick. No leeks or flooding going on. 6 gallons of gas gets me around about a 3/4 to maybe a 1 mile lake 6 laps or so. Is this normal? This is at about 75-90% throttle most of the time with about 6-8 starts from a dead stop.

Thanks

 

[john from md]

Re: Hey Frank, fuel starving at high rpm.

Do you have a tach on the boat? It would help to know what rpm you are getting at WOT. Another thing that can affect WOT operation is the pitch of the prop.

BTW, Force engines were never known for their economy.

On my '85 Bayliner with 85hp Force engine and smart tabs, I get three to four miles to the gallon when cruising at 27 MPH which is my optimum speed. That also assumes a pretty flat sea state. If I open it up to 40, I can watch the fuel gage move with the trottle.

Regards,

John