95 mariner 150 outboard hard miss at low RPM

[beaverlake66]

This is an oil injection carb engine that has a hard miss (skip) at idle when in forward gear running at 400/600RPM. Higher RPM gives no miss. Hot or cold makes no difference. Engine does not miss on every start up or low RPM operation. Any ideas on cause for problem?Ken66

 

[KCLOST]

Re: 95 mariner 150 outboard hard miss at low RPM

Take that baby into Jimmy Houstons shop and have them check it out!!!!! <br />Just Kidding....<br /><br />I would first check the spark on all the cylinders. And check compression while you are at it.. Go buy a spark gap tester at Napa or another auto parts store. Check each one at a time. Make sure that you start with a small gap, around 1/4". If you find a cylinder(s) that are missing a "consistent" firing condition, we can then backtrack the problem through the coils, switchboxes, and all the way to the stator if necessary.... By the way, 400-500 rpms at idle seems too low... It should be around 800... Check your manual to confirm...<br />Let us know...

 

[beaverlake66]

Re: 95 mariner 150 outboard hard miss at low RPM

Thanks for suggestions. The manual calls for 600/700RPM idle speed in forward gear. Will check all of your suggestions.

 

[KCLOST]

Re: 95 mariner 150 outboard hard miss at low RPM

A "hard" miss is most likely electrical... So do that spark testing. Follow the directions on the gap tester instruction.... Like I said, start with a small gap... You don't want the spark (if it's present) to not find ground, or that could damage the switchboxes... But if it's already missing, you'll know it...