8HP coughs and stalls when idling warm - will not restart unless Choke open

[watercruiser]

OK, I was a mechanic many years ago so I have some inclination but I lost most interest.<br /><br />I have detailed my problem fully so as not to get chance guessing here ...<br /><br />FACTS:<br />Just had some work done on it (long shaft extension and remote throttle) and my guy is now out of town for a week<br /><br />It's a mercury 1995 8hp 2 stroke but very low hours, clean new plugs.<br />New fuel tank<br />New fuel 50:1<br />New hose (very very very light leak next to bulb nothing major) about 3ft hose run to motor from tank<br />Engine starts from cold start everytime and ticks over (idles) nicely<br />Fuel Tank vent open !<br />Cooling working fine<br /><br />PROBLEM:<br />Took the boat out last night to try my new fangled remote control throttle and long shaft<br />Ran like a dream into the bay<br />Decided to do some integrity testing so I did some slow/fast runs, reverse runs into waves etc..in 2+ ft swell.<br />1st problem, I idled for a moment then went into reverse (it's a gear shift then throttle all in one manouvre)<br />Engine stalled, OK maybe too much current working on propellor ?<br />Tried again and managed to play around in reverse just to see it's performance. Not great but not bad. No issue.<br />Ran around a little more things seemed fine all in all.<br />2nd problem happened coming back to my slip<br />Slowed down to idle/neutral on approach. Engine seemed OK<br />The engine up to this point had been running for about 45 minutes no problem<br />Hit the gas in forward a little to keep momentum, and it stalled<br />Ran past T head and swung out for room<br />Tried starting, no joy, pumped the bulb a few times just in case of fuel starvation<br />ONLY way to start it was to pull out the CHOKE FULL and it started first pull<br />Turned off choke and it idled fine, put it into forward, same again STALL !<br />Had to do this about 10 times, managed to gun it into slip with wind and momentum<br />Havin tied up I tried motor again, SAME issue, wouldn't start but would start on CHOKE it starts without a problem<br />Leave it idle for about 1 min, it then COUGHS a little, then slowly dies down to stall<br />Start in with CHOKE again, try putting it in forward, and .. YES you guessed it STALL.<br /><br />SYNOPSIS:<br />So I have a warm engine that wont start unless you CHOKE on.<br />To me that's maybe an AIR problem ??<br /><br />So if any of you are guru's here do you have any good idea what it might be ?<br /><br />Sorry for the long tale I just want to avoid the usual suggestions like fuel/hoses/idle speed etc.<br /><br />Thanks for any helpers<br />Alan

 

[AndyL]

Re: 8HP coughs and stalls when idling warm - will not restart unless Choke open

It sounds to me like it is running too lean. Try backing off the mixture screw half a turn. Sometimes if they were set up on muffs in a workshop environment there is not the same hydrostatic backpressure on the exhaust which can effect the mixture. Give it a try and come back.<br /><br />Andy

 

[watercruiser]

Re: 8HP coughs and stalls when idling warm - will not restart unless Choke open

Thanks Andy,<br />I'll try tonight.<br />Just as a double check, would that problem not have been apparent during normal running ?<br />I guess that's the muffs issue ?<br />The motor did go from a 15" to 25" and the guy did mention he didn't see a good thrust, he may have tightened up some<br />Also is the mixture screw identifiable ? I don't have a manual (YET). I assume on the carb somewhere, is it easy to get to ?<br />Thanks again I'll let ya know<br />Alan

 

[AndyL]

Re: 8HP coughs and stalls when idling warm - will not restart unless Choke open

G'day Alan<br />The mixture screw is probably near the throat of the carb. It will be brass and your mechanical background should lead you right to it.<br />Good luck<br /><br />Andy

 

[watercruiser]

Re: 8HP coughs and stalls when idling warm - will not restart unless Choke open

Thanks Andy.<br />Well I did this, however I ended up turning CW a little (not CCW), this seemed to run better (gut feeling in the sound and pickup). Ran last night for about 45 mins under load stopping,starting, idling etc .. without a hitch so ..<br /><br />Appreciate your help !!<br />I did notice similar threads to your suggestion so I think you gave me the right advice.<br />Cheers<br />Alan<br /><br />P.S. Is that Guernsey in UK ? I'm an ExPAT from Sheffield. Been in US for last 6 yrs.

 

[AndyL]

Re: 8HP coughs and stalls when idling warm - will not restart unless Choke open

Sure is. Tiny little corner of paradise except in winter!!

 

[Merc805]

Re: 8HP coughs and stalls when idling warm - will not restart unless Choke open

If you turn it clockwise, it gets more petrol and CCW it gets leaner ? Am I right ? The setting is.. Turn all the way in and then out 1 to 1 3/4 turns out. Keep turning out until speed changes.

 

[watercruiser]

Re: 8HP coughs and stalls when idling warm - will not restart unless Choke open

I'm not sure, but it seems to run fine now. Basically I turned it in till it started to splutter, then turned CCW till it did the same, then it's somewhere between that. The end point was 40 degrees CW from where it was originally.