1969 mercruiser idleing

jurecki

Cadet
Joined
Jul 25, 2004
Messages
9
i have a 1969 mercruiser with a rochester 2 bbl carb and after 2300 rpms the engine will run perfect but below that it will just start cutting out and the rpms will decrease till it dies out i was wondering if i had a leak somewhere in the carberator or intake manifold
 

xltier

Chief Petty Officer
Joined
May 20, 2004
Messages
636
Re: 1969 mercruiser idleing

u could have a vacumn leak or the idle circuit in the carb. is plugged.
 

jurecki

Cadet
Joined
Jul 25, 2004
Messages
9
Re: 1969 mercruiser idleing

i have the idle screw all the way screwed in for the throttle and i can't get it to idle in the water while the engine is cold it will go than after it is warm it still start reving down than almost die than it will rev up to about 2000rpms than it rev back down and it will do that a couple of times than it will rev down a last time and it will idle rough for a couple of min than die out
 

rattana

Chief Petty Officer
Joined
Jun 12, 2003
Messages
413
Re: 1969 mercruiser idleing

Did you mess with the two idle mixture screws on the bottom of the carb? That will affect your idle speed circuit. You can try spraying a carb cleaner from autozone down the throat of your carb keeping your rpms up so it doesn't stall. A whole can may clean it out enough to clear the problem. If that doesn't work you may need a carb rebuild.
 

jurecki

Cadet
Joined
Jul 25, 2004
Messages
9
Re: 1969 mercruiser idleing

i took the carb apart and cleaned it with some rubbing alcohol and i have the screws set at around 1 and 1/2 that is what the manual said to put them i called mercruiser and they said they don't make that carb rebuild kit anymore
 

rattana

Chief Petty Officer
Joined
Jun 12, 2003
Messages
413
Re: 1969 mercruiser idleing

It is possible that you have a vacuum leak if any of the gaskets were in bad shape when you put the carb back together. To set the idle mixture screws you can try turning the idle mixture screws out a little to see if you can get it to idle. You want to set the idle mixture screws to maximum rpm. Keep turning the idle speed screw down to maintain 700RPM or so as you alternate back and forth adjusting the 2 idle mixture screws to get best smooth RPM. Once you have the best idle, you can turn both idle mixture screws in 1/4 of a turn so the idle mixture isn't too rich. Readjust the idle speed to 700RPM.
 
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