stalling

[jcalianos]

My a-4 has been stalling. Engine starts and idles fine. approx. 1 week ago, i noticed that past 1/4 throtle the engine would hesitate and backfire. I adjusted the main jet, assuming that it was running too lean. I was able to get it to run better, but not perfect. It would still hesitate. My mechanic suggested I add a water absorber feul additive. I did, and took the boat out to run it. I ran it at full,throttle,but it seemed sluggish. Suddenly it slowed down and the engine stalled. I could not start it for approx 10 min. Finaly i was able to start it with full choke only, but it would not run past idle. I sailed the boat back to its mooring with the engine at idle. when i moored , the engine ran better,full range of throttle, in full choke only. Now the engine will not even run without the choke. I think the main jet may be clogged. Is this the likely cause?

P.S. Prior to all this I installed a new alternator and choke cable.

[Don Moyer]

It does sound as though you have some crud trying to move through your main jet.

Adjustable main jets are somewhat more sensitive to smaller particulates than fixed main jets in that the annular space between the adjustable needle and the fixed jet is quite thin. Tiny particulates that would be able to move through the orifice of a fixed main jet (and out of harms way) will get stuck trying to get through the thin annular space around the needle of an adjustable jet.

Good primary and secondary filters will of course go a long way to remediate this problem, but if the crud is already stuck in your main jet, it will probably be necessary to back the adjustment way out to allow the crud to pass, or remove the jet assembly completely for cleaning.

Don