1976 Mercruiser 302 stalls at idle after letting off the throttle

[sacpdg]

I have a 76 searay SRV 220 with a Ford 302 and mercruiser 888, with a two barrell carb made by Rodchester. My boat runs great except wheh i slow the boat down and try to put in neteraul or under 5mph the engine stalls. The boat stars up after a couple rotations of the motor and will idle ok after that. I adjusted the choke but because of the change in temp when the motor gets warm, the choke is either too lose, or too tight when cold. Do i need to adjust the fuel mixture, or did my fuel pump take a crap. Thank you very much for your help.

 

[dubs283]

Re: 1976 Mercruiser 302 stalls at idle after letting off the throttle

when was the last full tune-up??

 

[haulnazz15]

Re: 1976 Mercruiser 302 stalls at idle after letting off the throttle

I doubt the choke has much to do with it as it should be fully open when the engine is warm anyhow and is likely electric, right? I'd be looking at tuneup items and possibly carb rebuilt for the idle speed jets.

 

[cyclops2]

Re: 1976 Mercruiser 302 stalls at idle after letting off the throttle

High engine vacuum will suck extra fuel from the fuel circuits. So by the time the engine is at idle extra fuel can be drawn in and changed to a very rich mixture. That will stop the engine with NO BACKFIRING.

2 common causes of over rich on slowing down are a over rich idle mixture, smoothed out by raising the idle speed screw.
Other cause might be a slightly high float level. Depending which way the float hinge pin is facing. That can cause the fuel to slosh away from the float, dropping it & the needle opens up & fuel starts flowing in. When stopped, the excess fuel sloshes the other way causing over rich condition. Restarts are quick.

Lean out the idle screws. Slightly rough idle at the right idle speed. If it still stops running.... Restarts might be harder, unless you pump the throttle.... I vote for a little high float level.

Carburator is old enough to have had a incorrect float setting from a rebuild over the years. I had a 460 Merc in a car where the float chamber gasket was not sealing whenever you floored it. Raw gas dribbled in to the engine.
That condition you have, should not be ignition problem.

 

[sacpdg]

Re: 1976 Mercruiser 302 stalls at idle after letting off the throttle

As far as the tint up goes, I just changed all the plugs and cleaned the wires, but I have not been able to find a new wire set yet I cleaned the distributor contacts and changed the oil.

I did just adjust the float in the carb to 1 9/32". Should I readjust the float. Could the line going from the back of the carb to the valve cover cause a vaccume leak.

Some times it starts back up easy. But sometimes it take a little starter fluid. Thanks for all the help

 

[sacpdg]

Re: 1976 Mercruiser 302 stalls at idle after letting off the throttle

As far as the tint up goes, I just changed all the plugs and cleaned the wires, but I have not been able to find a new wire set yet I cleaned the distributor contacts and changed the oil.

I did just adjust the float in the carb to 1 9/32". Should I readjust the float. Could the line going from the back of the carb to the valve cover cause a vaccume leak.

Some times it starts back up easy. But sometimes it take a little starter fluid. Thanks for all the help

Tune up not tint up.

 

[dubs283]

Re: 1976 Mercruiser 302 stalls at idle after letting off the throttle

well, you ruined the points by "cleaning" them - they wont last long now

when you tune-up, you replace the points/condenser, cap, rotor, plugs, wires, fuel filters, set dwell/timing, spray down the carb and adjust the idle speed/mixture

see here:

http://forums.iboats.com/showthread.php?t=335302

 

[haulnazz15]

Re: 1976 Mercruiser 302 stalls at idle after letting off the throttle

Please don't use starting fluid on a gasoline engine. Hell, it's pretty rough on diesels as well. If it's not firing off without starting fluid, you have an issue you need to correct.

 

[achris]

Re: 1976 Mercruiser 302 stalls at idle after letting off the throttle

... except wheh i slow the boat down and try to put in neteraul or under 5mph the engine stalls.....

Check your lower shift cable....

 

[Fishermark]

Re: 1976 Mercruiser 302 stalls at idle after letting off the throttle

Check your lower shift cable....

Yep - sounds more like the shift interrupt staying engaged too long instead of a tune up issue. A binding shift cable will cause that.

 

[cyclops2]

Re: 1976 Mercruiser 302 stalls at idle after letting off the throttle

Starter fluid & shifter delay switch ??

 

[sacpdg]

Re: 1976 Mercruiser 302 stalls at idle after letting off the throttle

I'm going to try the compete tune up and the shift cable adjustment. Is there a thread that shows me how to see if my shift cable is not adjusted right and how to adjust my shift cars. Thanks again. This help is truly appreciated.