2004 F8 4 Cycle won't idle (short shaft)

[tothemax]

I have completely rebuilt the carb - disassembled and dipped it, and on reassembly it still idles rough and stalls. The motor is getting good fuel, the float is set correctly at .77" (spec is between .75" and .79"). On the advice of a friend with a 9.9 outboard, he suggested that I may still have some gunk in the low speed passages. So I dipped it again yesterday and used carb cleaner afterwards to blow through all the air passages. I haven't tested it again yet. Hopefully this will make a difference.

But really did not see anything obvious - this motor has never been run hot, was bought new and has maybe 30hrs on it and always idled a little rough but did not stall like it does now - does not stall with the choke on. After the last carb rebuild the air mix adjustment had no affect. I don't see that I did much different this time - so if it still runs rough where do you suggest I look? The motor has good power after idle and runs better since the carb rebuild.

Thanks,

Mike

FYI: I replaced the plugs this season too... the motor has been mostly stored for the last 4 seasons, run a few hours a year on our dinghy.

[boats.net]

If runs ok with choke on then it still has plugged passages or jets in carb.

[tothemax]

The second clean out did it...

Boats.net,

2nd time I soaked it for a few hours then washed and blew it out. Then went through all jets and accessible passages with Gunk carb cleaner spray. Idles pretty well now, the only thing I notice is that it falters a little from idle on quick acceleration - go slowly and it rev's up fine (almost like the timing is a little retarded). I did make sure to run the carb dry since it would be sitting for at least a week. I'm wondering if I should start using additives in the gas.

Mike

[tothemax]

Is there and Accelerator Pump on the F8

After re-cleaning the carb - there is a hesitation on acceleration going from idle. It doesn't stall but it's close - someone mentioned that there was an accerator pump (diaphram attached to the linkage). I don't see one on my 2004 short shaft model. Once it revs up it runs pretty well - it's just going from idle that it starts to bog.

Any ideas? Thanks

Mike

[99yam40]

I am not familiar with your carb and motor, and do not know if it has an accelerator pump, but my opinion is:

You did not say if the idle mixture adjusting screw makes a difference now or not, if not then there is still a problem with the carb idle and off idle passages. Did you completely disassemble the carb when you soaked and cleaned it to make sure you got to all passages?
If it does make a difference then try adjusting the idle mixture a little on the rich side if you can and see if that helps the transition from idle to higher RPM.

[tothemax]

Rebuilt F8 Carb

Yes the air mixture screw does make a difference now, not a lot but screwing it in will make it idle rougher and sputter. It seems to run best at about 2 1\4 turns out. I can open it a little more to make it richer and try. There is a nylon plug in the top of the carb housing it looks like it is part of the idle circuit carb passages - I might need to replace it. I guess I could soak it one more time. I do completely disassemble it before putting in the dip.

FYI: The mixture screw use an O-ring rather than a spring to keep it in place - the stock one was too small and did not really keep any tension on the needle. I replaced it with a fatter O-ring and now adjustments seem to stay.

Thanks for the response,

Mike

[99yam40]

2 1/2 turns sounds kind of high, what does the manual say it should be? Normally it should be very close to factory spec. if working right. You may still have problems with the passages or a air leak.

[mrv8outboard]

Do you know if your fuel is E10? Because if it is you will find that it needs to be richer than normal.

[tothemax]

Reply

I don't see an accelerator pump - no linkage going to one. This carb only has a flat plate on top of it. I'm soaking again - giving it a couple of days.

MB