2003 johnson 90 hp j90plstc

buzzm19

Petty Officer 2nd Class
Joined
Dec 14, 2009
Messages
152
Hi guys, I have been trying to find out why this motor runs good cold and then when it gets hot it will miss slightly, in gear and at idol. When you throdle up it won't even get on plane and seems that the motor is severly miss firing. We idoled back to the dock and I checked it and the motor does not seem that its overheating, I pulled the plugs and there all soaked with gas to the point I can't believe it could run. I have been reading up on the optical sensor and power pack. It seems to me that the power pack (when going bad) only stops fire on a couple of cyls not all and why does it let the motor run at idol with the plugs being so wet. If the optical sensor is not advancing enough and it is mechanical and to me that would explain the wet plugs. I have heard that motor has a safe mode or sensor that prevents the motor running at higher rpms if the motor is overheating. Thanks any help Buz
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,033
Hook a timing light to each sparkplug.---------Run it up to full throttle on the lake and observe the flashing light.------Repeat with the other 3 cylinders.-----What do you observe during this test.
 

buzzm19

Petty Officer 2nd Class
Joined
Dec 14, 2009
Messages
152
Thank Racerone, I will check with a timing light, I think the problem is that its going into slow mode. His tac is not working but the constant voltage is 14volts. Does the tac trigger the warning horn? Thanks Buz
 
Top