[GRDANAPAUL]

New to forum looking for help on a 89 100 hp Mariner, variable rate oil injected. Intermittently 1 or more plugs will foul. After removing plugs and wiping off and cranking engine motor will work perfectly.Typically once motor gets "cleaned out" the motor will be fine all day. Occasionally if you have motor off for a couple of hours, say you are fishing, and start up it might fail. Motor always starts. I drained the fuel tank this spring, and filled with fresh fuel. I have rebuilt the fuel pump, tried new spark plugs. I use quicksilver oil. I have been through the carbs. It seems like excess injection oil is getting into the cylinders. Any ideas would be appreciated.
Dana

[Chris1956]

OK - First of all, when you stop for a while the gasoline will evaporate leaving a rich oil mixture.

Have you checked the linkage to the oil pump for proper operation? Also check your fuel line for air leaks. If there is an air leak in the gasoline supply, the oil pump will overpump oil.

[GRDANAPAUL]

I have checked and re-checked the linkage and alignment of oil pump linkage per service manual. You might be on to something w/ regard to air leak. The fuel line s on carbs have all been replaced and clamped/ tie wrapped . the fuel line and primer bulb to tank has been replaced also. I did run it last fall on a separate fuel tank and the problem seemed to go away, but it is an intermittent problem, that is what caused me to drain the on-board tank and fill with fresh fuel. The fuel does seem to drain out of carbs quickly. It seems if I pump the primer bulb prior to any start I can usually avoid the problem. Should there be a check valve in the tank that may be failing? Can I install a check valve in the line? Maybe o-rings on fuel fitting on engine connector? I will triple check those items.
I really appreciate this help.
Dana

[j_martin]

I'd bet on the check valve in the primer bulb being bad. Throw out that aftermarket chit and put on a mercury/quicksilver line.

hope it helps
John