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I am in a predicament with my Johnson GT 150. I am uncertain of its year but have had success with parts and diagrams from a 1986 so I am certain it is around that time frame.
I have done all the work on this motor for the past 3 years. When I purchased it barely ran and was able to bring it back and run it at min twice a month for 3 years. A quick list of what has been done in the past to get it running:
Power pack
Coils
Plugs
VRO delete (adding a two-pump set up each pump independent negative pressure port
Primer bulb and fuel lines to the motor
Rectifier
I had developed an issue while running 4000 – 5000 RPM where the motor would not die but lose power and act like it was missing or starving for fuel. If I pushed in the key primer, it would surge a tad but not fix the issue entirely. I would turn off the motor for a min and restart and it would run fine again. This issue became more constant. I felt as is the carb may have a sticking float or??. I rebuilt the carbs and that leads me to my new issue.
On Muffs or in my 150-gal tank boat starts and runs great. Put it in the lake and it will Idle fine, high idle lever up to any RPM, even throttle up in reverse. In forward gear the boat will not go above about 2000 RPM max speed if I have the controls is about 6MPH. I check the timing as best as I can without it being on the water, and it shows to be correct. Carb butterfly valves are completely closed when in neutral and perfectly horizontal at WOT. My original carb kits were not a Johnson / Sierra kit, so I purchased Sierra kits and rebuilt the carbs again with the better kits. I just replaced the throttle cable as the older one had more play than I felt acceptable. I replace the fuel pumps and plugs this weekend, and it help it idle better but did not make a difference on WOT.
Any ideas would be welcomed. Thank you in advance for your time and any help you can bring.
I am in a predicament with my Johnson GT 150. I am uncertain of its year but have had success with parts and diagrams from a 1986 so I am certain it is around that time frame.
I have done all the work on this motor for the past 3 years. When I purchased it barely ran and was able to bring it back and run it at min twice a month for 3 years. A quick list of what has been done in the past to get it running:
Power pack
Coils
Plugs
VRO delete (adding a two-pump set up each pump independent negative pressure port
Primer bulb and fuel lines to the motor
Rectifier
I had developed an issue while running 4000 – 5000 RPM where the motor would not die but lose power and act like it was missing or starving for fuel. If I pushed in the key primer, it would surge a tad but not fix the issue entirely. I would turn off the motor for a min and restart and it would run fine again. This issue became more constant. I felt as is the carb may have a sticking float or??. I rebuilt the carbs and that leads me to my new issue.
On Muffs or in my 150-gal tank boat starts and runs great. Put it in the lake and it will Idle fine, high idle lever up to any RPM, even throttle up in reverse. In forward gear the boat will not go above about 2000 RPM max speed if I have the controls is about 6MPH. I check the timing as best as I can without it being on the water, and it shows to be correct. Carb butterfly valves are completely closed when in neutral and perfectly horizontal at WOT. My original carb kits were not a Johnson / Sierra kit, so I purchased Sierra kits and rebuilt the carbs again with the better kits. I just replaced the throttle cable as the older one had more play than I felt acceptable. I replace the fuel pumps and plugs this weekend, and it help it idle better but did not make a difference on WOT.
Any ideas would be welcomed. Thank you in advance for your time and any help you can bring.