Slight miss in a Mercury 9.8

[robsd]

Well I finally got the 9.8 out on the river. The 32 year engine runs well. Nice speed with one person, decent speed with 2 people, dreadful speed with 3 people (max capicaty in a 14' john). No plaining with 3.<br /><br />The motor has a slight miss, sometimes worst than others. Always worst with a load on the engine (usally going up stream). Also only after it warms up a bit. I've got new plugs but they're not the flat type, the electrode sticks up like a regular sparkplug. <br /><br />Any suggestions. We've run it for the past 2 weekends with no problems. It'll idle as long as you want, starts on the 2-3 pull when cold and always the first pull when warm.<br /><br />Thanks,<br />Rob

 

[Chinewalker]

Re: Slight miss in a Mercury 9.8

Hi Rob,<br /> If possible, try running the motor at night and look for sparks arcing from the coils or spark plug wires to the motor block. Also, listen for arcing. The coils or wires may have some small holes/cracks that are allowing them to break down under load. If my math is correct, you've got a 1970 model which should have the maker-point magneto. Might want to clean up the points and gap them. If the green donut is going bad, there's no really cheap fix - they list over $200! Hopefully it's a simple thing...<br />- Scott