1988 Johnson 20hp Frustrated.....

[gnarbrah]

Hi all - Long story short I have this motor and it's driving me crazy. If you look back at my other posts you'll see the progression. Current Issue - I took the boat out 2 weeks ago and it ran great! 1 week ago I went out again and it wouldn't run right. Basically it started up and I idled out then when I throttle up it dies. I brought it in and thought I found the problem which was the butterfly in the carb. At full throttle it was just over halfway to horizontal. I adjusted it back to where it was horizontal at full throttle (why would this have changed in 1 week after it ran great? - I have no clue unless the set screw was loose somehow?) and assumed this was the problem. Excitedly I took it out today and it ran even worse. Occasionally I got it to idle nicely but it would never throttle up. To get it to idle I had to prime then adjust the slow speed needle to about 1/2 to 3/4 turn out from fully closed. I know the book says to start at 3.5 turns out and adjust from there but I couldn't get much with it that rich. What could cause the motor to just die out as soon as I try to throttle up? I rebuilt the carb last July or so and I'm hoping that should still be ok. I figure it has to be fuel / air problem or spark. What else is there and where to begin???

Thanks!

 

[jbjennings]

Re: 1988 Johnson 20hp Frustrated.....

I believe you have bad gas, water in gas, problems with old fuel lines and ethanol fuel., or just a dirty carb.
Either way, rebuild the carb. and replace all fuel lines with ethanol resistant ones if not already done. Sounds like your carb. is dirty.
JBJ

 

[SparkieBoat]

Re: 1988 Johnson 20hp Frustrated.....

yep

 

[5150abf]

Re: 1988 Johnson 20hp Frustrated.....

Link and sync maybe, if your timing and throttle aren't real close they run really bad so make sure those are synced right, you could be advancing the timing ahead of the gas or vice versa.

And you could easily have something blocking a carb especially if you haven't changed all your gas line.

 

[gnarbrah]

Re: 1988 Johnson 20hp Frustrated.....

Thanks for the input. The gas is new so that shouldn't be an issue. I'm leaning towards a lync and sync type problem or the carb got dirty somehow. I replaced the fuel pump last summmer when it started acting up originally. Didn't replace the fuel lines though. Obviously didn't help. I noticed yesterday alot of unburnt fuel (guessing?) coming out from the prop area (see pics). Does this narrow anything down? Thanks

 

[SparkieBoat]

Re: 1988 Johnson 20hp Frustrated.....

unburnt fuel is normal in small amounts there.

 

[buster01]

Re: 1988 Johnson 20hp Frustrated.....

Hey,

I just bought the same motor, I noticed on the left side of the lower end, just forward of the water intake vent, there is a small (1/8" dia) port, what is this port for?