1984 Mercruiser 140 runs great for 30-40 minutes, then stalls out

[adruid]

My 1984 Marathon 2200 Starfish walkaround fishing boat will start and run fine for about 45min. at 3500RPM then stutter, lose power and die. After running on the kicker, or fishing for about an hour, the engine will start up easily and run for another 45min. or so, then stutter and die again. I am very confused why this is happening. At first I thought it might be because the cut-off switch was adjusted incorrectly, and decelerating was engaging the switch. After adjustment, it does not die on deceleration until run for 45min. There is a spring assist on the new cut-off switch unit, and I wonder if the heat from the exhaust manifold is affecting the function of the switch unit. Has anyone had an experience with this type of behavior? Can anyone think of what may be causing this failure? Do boats experience vapor lock? Could this factor in? Please help, I?ve run out of ideas. Thanks for any input you may offer. Details of the engine and other components are as follows.

1984 Mercruiser GM 140 3L 4 cylinder engine S# 6821548
Mercruiser Sterndrive S#: 6821876
Upper Outdrive: # 637550 Alpha 1
Lower Outdrive: R

The engine had a valve job in August of 2014. All control lines, and main control unit were replaced at this time. New thermostat housing and thermostat 8/14. New engine mounted cut-out switch unit # 864363A1 installed 8/14. Pertronics electronic ignition system installed into Delco Remy distributor body, with Pertronics coil 9/14. New Rochester 2-barrel carburetor installed 9/14. New water pump #46-96148T8 installed 10/14. New plugs, wires, rotor, oil and water filters installed 11/14.

Craig D.

 

[Bondo]

Ayuh,..... Right when it Dies,.... Is there gas in the carb,..?? Is there Spark, at the spark plugs,..??

 

[boozer1966]

You are describing my problem almost exactly on my 1984 Mercruiser 140. When my problem starts, any electrical load, like hitting trim button makes it very much worse. There is fuel in the carb and I installed a fuel pressure gauge, so I'm pretty sure it's an electrical problem. I also have spark. Ground fault?

 

[Bondo]

You are describing my problem almost exactly on my 1984 Mercruiser 140. When my problem starts, any electrical load, like hitting trim button makes it very much worse. There is fuel in the carb and I installed a fuel pressure gauge, so I'm pretty sure it's an electrical problem. I also have spark. Ground fault?

Ayuh,.... My guess is you have a Bad Ground,....

I Know yer hi-jackin' adruid's thread,....

So, if this post don't give ya want ya need, start a thread of yer own,...
Don't post back in adruid's thread,....

Thank you,...

 

[achris]

My 1984 Marathon 2200 Starfish walkaround fishing boat will start and run fine for about 45min. at 3500RPM then stutter, lose power and die. After running on the kicker, or fishing for about an hour, the engine will start up easily and run for another 45min. or so, then stutter and die again. I am very confused why this is happening. At first I thought it might be because the cut-off switch was adjusted incorrectly, and decelerating was engaging the switch. After adjustment, it does not die on deceleration until run for 45min. There is a spring assist on the new cut-off switch unit, and I wonder if the heat from the exhaust manifold is affecting the function of the switch unit. Has anyone had an experience with this type of behavior? Can anyone think of what may be causing this failure? Do boats experience vapor lock? Could this factor in? Please help, I’ve run out of ideas. Thanks for any input you may offer. Details of the engine and other components are as follows.

1984 Mercruiser GM 140 3L 4 cylinder engine S# 6821548
Mercruiser Sterndrive S#: 6821876
Upper Outdrive: # 637550 Alpha 1
Lower Outdrive: R

The engine had a valve job in August of 2014. All control lines, and main control unit were replaced at this time. New thermostat housing and thermostat 8/14. New engine mounted cut-out switch unit # 864363A1 installed 8/14. Pertronics electronic ignition system installed into Delco Remy distributor body, with Pertronics coil 9/14. New Rochester 2-barrel carburetor installed 9/14. New water pump #46-96148T8 installed 10/14. New plugs, wires, rotor, oil and water filters installed 11/14.

Craig D.

Blocked fuel tank vent?

 

[boozer1966]

Ayuh,.... My guess is you have a Bad Ground,....

I Know yer hi-jackin' adruid's thread,....

So, if this post don't give ya want ya need, start a thread of yer own,...
Don't post back in adruid's thread,....

Thank you,...

With all due respect, he asked if anyone had experienced similar behavior and if anyone had any ideas about what it could be. I was simply answering the questions posed by the author while explaining the similarities of our problems. I thought that's what this forum was for?

 

[adruid]

Gas and spark are present, but it idles very rough. Sometimes it dies fairly quickly, other times I just turn it off to let it rest. Fuel tank vent is open, free of obstruction. Would it be able to idle, even roughly, with a bad ground? Thanks for the responses, guys!

 

[achris]

Throw a timing light on it. That will at least give you an idea of whether spark erratic-ness is behind the problem.

 

[adruid]

Timing is right on 6 degrees BTDC at idle, but I'll take the light out on the water to see what it reads when engine sputters. Also thinking of replacing oil pressure and water temp. senders. One tech told me to leave off the spring assist on the cut-out switch assembly, so I'll try that too. Have noticed that the lower butterfly in the carb. body is closed when this is happening. Going to leave engine uncovered, so I can get to things quickly for a better look.

 

[achris]

Oil and water temp senders have nothing to do with fuel or ignition. Removing the spring assist will also have the same result.

 

[adruid]

Right you are, achris. Looking into the carburetor at this point. Engine seems to be choking when the stall starts. Any ideas on what to look for? Went through the cycle Friday. Got to stalling time and dropped the RPMs down. Engine stayed running and was happy in the 2000 range. Oil pressure at 30psi and water temp. at 170. A friend was with me and talked about choking problems with older cars; may be a connection.

 

[nola mike]

Did you put the timing light on while having symptoms? Have you tried opening the gas cap (clogged vent?). Can't think of what would cause your symptoms within the carb itself if it runs for 40 min.

 

[adruid]

This particular model of I/O combination is a hybrid of the R series and the Alpha series. There are unique sections of the wiring harness and other components that don't seem to adhere to the specs. of any others. Still working on a problem that most of the folks who own this small range of years speak of, with much confusion and annoyance, in other forums as well. Thanks to all who have responded. Yes I/we have tried these fixes/approaches, but are still in the dark as far as a resolution. Keep On Keeping On!