1984 35 hp cough/sneeze

[Capt.Bud]

This motor is new to me even though its 37 yo. Just took it out for first time and it has a cough or sneeze what ever its called maybe backfire that occures at about 1400 - 1500 rpms and higher. It is fairly vialent..I am not leaking any fuel from engine fuel lines and the bulb pressure does not change. I set the timing where the roller is between the two marks and the butter fly on card just starts to move as you increase the trottle. If it means anything, imediately after a cough its seems to increase RPMs very slightly. Help its fishing time.

 

[oldboat1]

lean sneeze. If you have an idle mixture needle on top of the carb, set is slightly richer (1/8 c.clockwise at a time) until the noise goes away. At idle, in gear, warmed up.

 

[Capt.Bud]

lean sneeze. If you have an idle mixture needle on top of the carb, set is slightly richer (1/8 c.clockwise at a time) until the noise goes away. At idle, in gear, warmed up.

I have no sneeze at idle, only when RPMs get over 1400. I did check compression when I got back and it was 135 both cylinders and plugs looked alike with tan electrode and slight wet on outer parts of plugs.

 

[oldboat1]

Sounds ignition related, then (though could be a bit of something in the h.s. orifice). Champion plugs at .030 gap? If it feels like you are hitting something with the lower unit, it may be the clutch dog.

 

[Capt.Bud]

Sounds ignition related, then (though could be a bit of something in the h.s. orifice). Champion plugs at .030 gap? If it feels like you are hitting something with the lower unit, it may be the clutch dog.

I had a weak intermittent spark on #1 cylinder and replaced coil and CDI and that cleared up nicely. I have new champions gaped at .030

 

[oldboat1]

Well, oem fuel pump kit is about $20, and may solve problem. Increase in rpm can indicate a lean condition, as when you remove the fuel line to empty lines, and the engine speeds up just before shutting down.

 

[Capt.Bud]

Well, oem fuel pump kit is about $20, and may solve problem. Increase in rpm can indicate a lean condition, as when you remove the fuel line to empty lines, and the engine speeds up just before shutting down.

will order kit tonight and change hose from tank to motor. I do appreciate all of you taking time to help me out.

 

[saltchuckmatt]

I had a weak intermittent spark on #1 cylinder and replaced coil and CDI and that cleared up nicely. I have new champions gaped at .030

OMC ran a service bulletin on that engine. You are supposed to run the timing mark up 1/4 to 1/2 an inch when setting that mark. Mine had the same problem and worked correctly after resetting to that mark. Lots of info on the web related to what I just said.

 

[oldboat1]

Timing refers to spark timing with respect to piston position (eg. 4 degrees before top dead center), not the intensity of the spark.

 

[racerone]

I believe the reference was to changing the point where throttle plate opens.