Hello, I recently started working on a 96 Johnson V4 90hp on a pontoon that had been sitting for a number of years. To get it running I replaced the fuel lines, drained the tank, cleaned the fuel strainer (only filter on boat), changed drive lube, replaced plugs, cleaned carbs, and replaced battery. I have run the boat a few hours and it runs ok at half throttle. If I run at full throttle the engine will run fine for a few mins and then start to intermittently misfire, run fine for 30 seconds, have a misfire fit, run fine, and so on. I have swapped the two coil packs around and replaced the stator thinking it might be bad (it looked a bit melted) and it may have improved but not fixed the issue. The tach doesn't work but the battery charges and the volt gauge reads 14ish when the motor is running so I do not think the rectifier is bad. Here are some other comments:
-I have not checked the compression or replaced all of the jets in the carbs but I wouldn't think that is my issue since it will run fine, misfire, then run fine again and is linked to the motor heating up.
-The warning alarm system works and it does not give a temperature warning when it starts to misfires (but maybe the temp sensor is bad and motor is in fact getting too hot?).
-VRO is still hooked up and seems to work fine.
I think this must be related to some electrical component heating up and causing erractic spark. My thought is that the issue being temperature related and intermittent rules out fuel supply, carbs, and compression (tell me if I am wrong). I have not replaced the impeller.
Let me know if you guys have any ideas.
-I have not checked the compression or replaced all of the jets in the carbs but I wouldn't think that is my issue since it will run fine, misfire, then run fine again and is linked to the motor heating up.
-The warning alarm system works and it does not give a temperature warning when it starts to misfires (but maybe the temp sensor is bad and motor is in fact getting too hot?).
-VRO is still hooked up and seems to work fine.
I think this must be related to some electrical component heating up and causing erractic spark. My thought is that the issue being temperature related and intermittent rules out fuel supply, carbs, and compression (tell me if I am wrong). I have not replaced the impeller.
Let me know if you guys have any ideas.