93 johnson bogging down

[Johnson Marine]

i have a 93 3hp johnson that runs great at idle and half throttle. But the more the throttle is increased the more it bogs down and sometimes cuts off. I changed the fuel filter and cleaned the carb. any advice would help.

 

[Mntom]

Re: 93 johnson bogging down

Sure sounds like some gunk in the high speed jet. When it bogs have you tried to hit the choke for a second? If it is a lean condition then it should pick up and run better for a few seconds.

 

[Johnson Marine]

Re: 93 johnson bogging down

i havent tried that yet. I have took the carb completly apart and blew compressed air through everything. I am gonna replace the gasket on the carb tomorrow.

 

[Johnson Marine]

Re: 93 johnson bogging down

I put a carb kit on it. And i tried pulling out the choke when it bogs down and the motor cuts off. So i dont think its the carb. Any ideas?

 

[Daviet]

Re: 93 johnson bogging down

Does it actually shut down or just miss?

 

[Johnson Marine]

Re: 93 johnson bogging down

It shuts down

 

[Daviet]

Re: 93 johnson bogging down

You're sure it's a fuel problem? Have you checked spark when it happens just to be sure? If the spark is there then I would think that you are fighting a fuel problem. Have you checked the fuel pump pressure, maybe the gasket between the pump and block is leaking? You might try running the engine and just when it is about ready to stall, squirt some fuel mixture into the carb and see what happens. If it picks up and runs you have a carb problem. When you had the carb apart did you remove the orifice in the high speed nozzel and make sure everything was clean and there were no restrictions?

 

[Johnson Marine]

Re: 93 johnson bogging down

I have good spark and the plugs are brand new. I cleaned the orifice and high speed nozzle. I will try to spray the carb when it trys to shut off and see what happens.

 

[Johnson Marine]

Re: 93 johnson bogging down

I just went and sprayed the carb when it bogs down and the motor cuts off again.

 

[Daviet]

Re: 93 johnson bogging down

This may sound silly but is the throttle plate opening completely, 90 degrees to the carb bore?
Will the engine start right back up after it stalls, do you have to choke it or anything?

 

[Johnson Marine]

Re: 93 johnson bogging down

i will check the throttle plate. It does start right back up after stalling. Sometimes i have to use the choke but not alot.

 

[Daviet]

Re: 93 johnson bogging down

Also make sure the timer base is moving to the WOT position.

 

[Johnson Marine]

Re: 93 johnson bogging down

It does go to the wot position. I dont know what else it could be. It runs too good at idle and half throttle to be a fuel problem. And the throttle plate opens 90 degrees

 

[Daviet]

Re: 93 johnson bogging down

Man, what a stinker. I am going to try and find a manual and do some research. Will get back when I have more info.

 

[Johnson Marine]

Re: 93 johnson bogging down

OK thank you very much. I also ran a compression test and got 70psi in both cylinders so i have good compression.