60 HP Mariner Bigfoot sparkplug problems

jonjonC · 14 April 2011, 18:49

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 · 14 April 2011, 18:59

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 · 15 April 2011, 10:53

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 · 15 April 2011, 13:57

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?