60 HP Mariner Bigfoot sparkplug problems

[jonjonC]

A while ago I was motoring back to the marina when the engine suddenly slowed - sounding as if it was only firing on 2 of the 3 cylinders and this meant that I could only make 6 knots. Changed the plugs and problem solved. However, with only about 15 hours running on the new plugs the problem recurred. This time I changed the plugs whilst at sea and again problem solved. I showed the used plugs to a mechanic (not a marine mechanic) friend of mine and he said that they were excessively oily, to clean and re-use them OR to try some hotter burning plugs. What do you guys think? I'm currently using the recommended NGK BP8H-N-10 plugs. If I need hotter ones can anyone tell me what to get? Thanks in anticipation of your words of wisdom.

[neil.mccrirrick]

It could be the plugs but its more likely your air mixture is wrong, or the air intake is blocked. Does it idle well or sluggishly?

Ideally your plugs should be a light brown

[jonjonC]

Many thanks Neil, It has always been a bit lumpy on tickover - sometimes cutting out at extremely low revs when in or out of gear. I'll check the air intake as you suggest. Hopefully that will sort the problem. Thanks again.

[uncle al]

you have the correct factory recommended s/plugs fitted,what colour spark plug electrodes? is the timming correct ? (checked with a strobe light?) are the carbs syncronised?does it run ok if you keep preasure on the primer bulb?