Merc dies when you put it in gear

[kingfishnc]

1975 75 hp Mercury-- Starts but runs only with choke fully out- then stalls out when you shift into gear (either forward or reverse). Any tips on this?

 

[emckelvy]

Re: Merc dies when you put it in gear

There was no 75 HP Merc made in 1975, maybe you mean 85 HP? Or was it 7.5? At any rate, go richer on the idle mixture settings and maybe that'll help. For each carb, turn the mixture adjust screw (at approx 1-o'clock position on the carb) 1/8 turn CCW. This will richen it up a bit, these motors have no accelerator pump so if they're too lean they'll bog. Try in gear and acceleration, repeat until you get improvement.<br /><br />You may need to turn your idle speed up also, for a more stable idle.<br /><br />Note that if the idle mix adjustments don't help that much, you may have deeper carb issues or other internal probmlems. A compression test will rule out cylinder sealing issues.<br /><br />This still applies even to a smaller, single-carb model. <br /><br />HTH and let us know how it turns out........ed

 

[Darryl34]

Re: Merc dies when you put it in gear

I would look at my idle rpms first,your probubly idling too low.

 

[kingfishnc]

Re: Merc dies when you put it in gear

Thanks for the advice- but wouldn't you know that after pulling the boat home and put the muffs on -- it ran great!! Only thing I can figure is it must have had some trash in the tubes somewhere and the jolting of the ride home must have shook it loose. Anyway, thanks for the help..

 

[watercruiser]

Re: Merc dies when you put it in gear

OK, I was a mechanic many years ago so I have some inclination but I lost most interest.<br /><br />I have detailed my VERY similar 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 /><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 no 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