1992 Johnson Oil Fouling

[dustyrector]

I recently purchased a 17.5' Cajun with a 1992 115hp johnson outboard. I have been having some power problems when starting from a stopped position. The boat will not plane out quickly. So far I have replaced the plugs. Next time I go out I am going to De-Carb the motor, and I have recently changed the fuel filter, but I haven't taken the boat out since I did that. The boat currently runs around 5000rpm WOT. After we went out last, I pulled a plug to see haow it looked and noticed that the plug was oil fouled as were the other plugs. The engine has oil injection (I think). Are plugs supposed to be oil fouled with this type of engine? Could this be causing my power problems? If not, what should I do at this point?<br /><br />Thanks,<br />Dusty

 

[wilde1j]

Re: 1992 Johnson Oil Fouling

I would suggest you find the oil reservior and check the oil level first.<br /><br />Fouled plugs can result from a number of things, such as prolonged trolling/low speed operation, excessive oil in gas, etc. Before doing anything too drastic, try to confirm oil consumption. Put a mark on the oil tank where the oil level (should be full or close to it) is and use 75 to 100 gal of fuel. Keep track of fuel and refill the oil tank to the mark, keeping track of the amount of oil put in. <br /><br />Decarbing is a good idea, if you don't know when/if it was done prior.<br /><br />Once you are reasonably sure the motor is running good, you should try to trim for max RPM's at WOT. Your motor should run about 5800 RPM WOT with a normal load. If it doesn't, you need to reduce prop pitch. 1" of pitch reduction should yield ~ 150 to 200 RPM increase. Before getting another prop, you need to check how high the motor is mounted. The cavitation plate with the plate horizontal should be at or above the hull bottom. By the way, a lower pitch prop will improve acceleration from dead stop.