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1986 Johnson 40hp won't run past half throttle, alarm sounds

T

Throbbin Rods

New member
I am working on my son's boat and running into an issue. It is a 1986 Johnson 40hp. Motor used to run perfect but sat for 5 years. I have cleaned the carbs 5 times. Motor will run perfect until about half throttle. Beyond that it will surge, revving up and dropping back. In addition the low oil alarm goes off the entire time the motor is running in the water. The motor has had the VRO removed and runs on pre mix, not something I did. The wiring harness from the fuel pump has 4 wires. My understanding is that the purple wire is the power feed to the alarm horn for all conditions so I don't want to disconnect that. Motor has a new impeller, pees water as it should and I can lay my hand on it for an extended period of time while it's running. I am wondering if the motor might have gone into safe mode with the VRO removed and that might be the problem with running at high speed? I am just about to pull the carbs again for a sixth cleaning to ensure the high speed jets are clear. I would appreciate any thoughts or suggestions anyone might have.
Thanks,
Bill
 
Wrong.-----You disconnect wires going to the module on the VRO.----Overheat will still sound.------There is no " safe mode " function on your motor !!---If you have cleaned the carburetors 5 times then maybe it is NOT a carburetor issue.-----Post the results of a compression test ( 140 PSI ? ) or better.-----Test run with another hose and tank as well.
 
Racerone, just to be clear should I disconnect the 4 wire connector coming from the pump? Again, I did not remove VRO from this motor, it was like that when we bought it.
Compression numbers are 140 and 142. I neglected to mention that I replaced the coils last week. Previously it was running on one cylinder and the coils were bubbled underneath as though they had been too hot. New coils corrected the running on one cylinder issue. Tried with another tank and hose, no difference. I would like to resolve the warning horn issue before I try anything else.
Thanks much,
Bill
 
Sorry ----I can not see , feel or hear your motor.------Can not look over your shoulder !----Flywheel key sheared perhaps ?-----Is ignition advancing all the way ?-----Throttle plates both opening fully ?----Spark still good today ?-----Compression good today ?-----Crankcase compression good today ?-----Too little fuel ?----Too much fuel ?------In my opinion this should be an easy fix !
 
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