Can a sparkplug gap cause vibration?

[rsimmons42]

I recently ordered the OMC Service Manual for my motor. 1977 70 hp johnson.

The service manual says .040 gap on the plugs, everything else I read says .030.

I pulled the plugs and gaped to .040. I then went on the water and the engine had a vibration that I could feel through out the boat. Can a gap cause this vibration.

Checked plugs when I got back, no fowling.

Or can the timing being off a bit cause this vibration.

 

[tashasdaddy]

Re: Can a sparkplug gap cause vibration?

they run better gapped at .030. unless it is missing, i it should not cause a noticable vibration, i would check the prop for damage, even a bent prop shaft.

 

[rsimmons42]

Re: Can a sparkplug gap cause vibration?

i checked the prop, it is in excellent condition, and I ran a true line across the center of the prop shaft and spun it. it is holding true. IS there a torque value for the prop nut on this engine 1977 70hp johnson.

 

[rsimmons42]

Re: Can a sparkplug gap cause vibration?

thr prop is in excellent condition, and I did test the prop shaft, is there a torque vallue on the prop nut for this engine 1977 70 hp johnson.

and can the timing cause the vibration. I am in the process of adjusting the timing due to replacing the Stator, Timing Base, Power Pack and the Coils

 

[tashasdaddy]

Re: Can a sparkplug gap cause vibration?

any type of mis firing can cause vibration. but what you are saying seem intent. did you torque the flywheel to specs? i have always just tighten my props down, to the nearest space for the cotter pin.

 

[rsimmons42]

Re: Can a sparkplug gap cause vibration?

yes, The torque value said 100ft/lb I torqued to about 120