merc 850 stalling

[ouchita]

i have a 1976 mercury 850 thunderbolt it stalls when i put it in gear i am thinking it could be the coil trigger any ideas or opinions greatly appreciated

 

[Fuzzytbay]

Re: merc 850 stalling

I'd be thinking its more likely a carb problem. A bit more info on the how's of your problem might make it easier to diagnose.

 

[ouchita]

Re: merc 850 stalling

i have to idle the motor up to get it in gear without stalling once i get it in gear it runs perfect it also idles smooth its like the timing doesnt advance when i put it in gear

 

[Fuzzytbay]

Re: merc 850 stalling

Idle up/ do you mean you have to use the fast idle lever to raise the rpms?
When it does go into gear, does it grind?

 

[ouchita]

Re: merc 850 stalling

Yes I raise the idle up lever and it goes in gear it does not grind it does slam though obviously because I have th RPMs raised

 

[jeff_smith_0423]

Re: merc 850 stalling

Look on that block for any vacuum lines that could be suspect as well. I had a '77 that I couldn't get to run right (exact same behavior pattern) and sold prematurely. The next owner fixed it with 10 inches of cheap vacuum hose. I was sick for weeks, but the new owner is a good guy.

 

[Fuzzytbay]

Re: merc 850 stalling

If thats the only issue, you may just have to increase the base idle rpm.

 

[ouchita]

Re: merc 850 stalling

I did find a vacuum hose broke in half i will try that tomorrow if the weather holds out if that is not my problem what would be a safe base RPM to set.
Thanks for all the help.

 

[jeff_smith_0423]

Re: merc 850 stalling

Good to hear you found the hose in question. Still makes me sick to think about selling that boat. 850-900 rpm out of water is a good place to start.

 

[Moody Blue]

Re: merc 850 stalling

Where is that line located? I have a similar stalling problem and this might be the cause. I've exhausted most other causes, I think.

 

[ouchita]

Re: merc 850 stalling

The vacuum line is directly behind the switch box if you look on the right side of it . I fixed the line and tried it out today and no luck. Keep me informed of anything you come across that fixes the problem it realy sucks because the motor runs like a dream other than that.

 

[Moody Blue]

Re: merc 850 stalling

I have basically the same motor, a 1971 Merc 800. Has been driving me nuts the past summer. Starts easy and idles well. Put it into gear and it stalls right away. If I goose it just a little when going into gear it will keep running and idle fine in gear after that. It is ONLY when shifting into gear that causes it to stall.

I have performed the sync and link procedure numerous times with no luck. I really have not spent alot of time trying to sort it out but my hunch is that it is an ignition/carb sync issue.

Taking the carbs and fuel pump off to rebuild this winter on the chance the previous owner messed something up.

 

[Fuzzytbay]

Re: merc 850 stalling

Moody B and ouchits What is the rpm you have right now, (if you have tach's) Rpm should be around 700-900 as low range to high. Only other thing I could think of would be a leak on the carb seals, or reeds. Have you tried to richen up the carbs a bit past best idle? Last but not least, what octane do yuo use for fuel?

 

[ouchita]

Re: merc 850 stalling

My idle is up to 1000 as of yesterday I have not messed with the carbs and im running 87 octane

 

[Johnw452]

Mercury 85 hp thunderbolt Just bought my 1st boat with the same problems runs perfect on muffs but stalls in water as soon as I put it in gear. Tried new carbs new spark plugs compression test was good new stator and new primer bulb. Only thing I notice is bulb doesn’t hold prime when connected to motor? Offline it gets hard.

 

[GA_Boater]

Mercury 85 hp thunderbolt Just bought my 1st boat with the same problems runs perfect on muffs but stalls in water as soon as I put it in gear. Tried new carbs new spark plugs compression test was good new stator and new primer bulb. Only thing I notice is bulb doesn’t hold prime when connected to motor? Offline it gets hard.

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