Outboard stalls when idling low rpm

[rob.s.uk]

I've just got hold of an old selva 170 9.9 2 stroke. When started it will run fine if revved and works fine when in gear at revs. Sometimes it will tick over other times it stalls. I also noticed if you go out for a run as i slow down to low rpm it will stall. It starts back up fine. I was wondering if it's the fuel pump diaphragm as I've had that before on other engines. When the engine is at high rpm it would pump fuel but at lower rpm it couldn't pump enough to keep the engine running. I have cleaned out the carb and I think it's adjusted ok. I was also thinking air leak. Any suggestions.

 

[gm280]

rob, you could test the fuel pump with a pressure gauge to see what it is doing. But I feel your real problem is in the carb yet myself. Something isn't adjusted right with it in my opinion. JMHO!

 

[rob.s.uk]

The only adjustment on the carb seems to be the idle screw well I think that's what it is. Maybe it's the mixture screw rich/lean. I'm not sure. When screwed in the revs drop and screwed out they increase. I found somewhere on the internet it said to set it 1 1/4 turns out from closed. It seems ok like that as when it is idling it sounds ok. I had it idling for around 15 mins earlier but it will usually bog and stall like fuel starvation. The only other screw is the throttle stop.

 

[tomhath]

Sounds like it might be running a bit rich. The 1 1/4 setting is just to get you started, you adjust it from there to make it run best - every motor is different. Try screwing it in a little, if it backfires (sneezes) you went too far.