8 hp Surging Johnson

[brackley]

I'm new to outboard motors, but not to motors in general and am having an issue with an '85 Johnson 8hp outboard.

The engine/thrust surges at all throttle positions and in neutral/forward/reverse.

The primer bulb is tight and the ss/needle valve has been adjusted in order to keep it running as best as possible.

We would get a second or two of full thrust followed by what sounded like the engine was starved for fuel. But what was weird is the gaps between thrusts kept getting smaller until it went wide open and operated great for about 30-45 seconds and then went back to surging.

The gas tank and associated fuel lines are pretty old and felt like they were too small for the connection to the motor. Could the motor not be getting a good fuel supply.

I appreciate any help you can provide.

Thank you,

 

[brackley]

Re: 8 hp Surging Johnson

Does this sound familiar to anyone?

Thanks for the help,

 

[the machinist]

Re: 8 hp Surging Johnson

Generally fuel pumps work or they don't. Have you tried keeping the primer bulb pumped up as it it acting up. If that helps it is the fuel supply. Under normal running, the primer bulb should loose it's hardness once the motor runs a bit, but should not be hard all the time. Other than that the indications point to a dirty carburetor.

 

[SolingSailor]

Re: 8 hp Surging Johnson

Possibly a stuck float valve?

 

[brackley]

Re: 8 hp Surging Johnson

Possibly a stuck float valve?

I kept trying to pump the primer bulb while the motor was surging and when the motor was full out running flawless (just to see the difference) and the bulb was tight during both.

I'm going to replace the fuel lines going to the motor and all tank fitting to see if this is the issue. If that doesn't work, then it's on to the dreaded carb.

I agree I don't think it's the fuel pump due to the nature of it working sometimes and then surging other times.

Thanks again for the help,