Won't go over 1/4 throttle 1985 Johnson 30hp model J30ELCOA

[fenderfuel]

So I bought this boat a year ago and I only just got it on the water this year after refurbing it. The motor would only run up to 1/4 throttle then after that it would rev up momentarily, then bog down and surge. I figured it was a simple carb issue, so I cleaned that twice with compressed air, carb cleaner, and an ultrasonic cleaner. Its really clean. Motor starts right up, idles low and doesn't surge or have a rough idle. Anyways, I noticed the fuel line from the gas tank to the motor was leaking slightly when under full pressure of priming, so I replaced that and added an inline fuel filter just after the primer ball before it goes into the cowl.

Now, the motor will start up and run for about 10-15s in neutral, then bog out. Compression test was 125psi in each cylinder, there was spark on both cylinders, so I am guessing its a fuel issue. Does anyone else concur? any other ideas?

 

[fenderfuel]

thought i messed up the timing too, but just realized it was just the forward reverse adjustment...

 

[pro-crastinator]

If it were me, I'd take out the inline fuel filter and give her a go.
Its just an untested variable thsat you dont need at this stage.

 

[fenderfuel]

Yeah I was thinking the same thing til i was priming the bulb and realized the fuel pump was spraying gas out of the fitting. Going to pick up a new one and see how it goes.

 

[fenderfuel]

Ok, so new fuel lines, new fuel pump, no change. Still won't rev up. Any other ideas? I'm thinking power pack might be bad. I replaced the spark plugs and wires too, but that didn't help either.

 

[bonz_d]

Compression numbers look good. You say it is getting good spark so that only leaves fuel. By the model number I'm guessing this is a remote engine and not a tiller.

Take the cover off and then watch the throttle linkage at the carb, try to determine if the carb butterfly is opening all the way when you move the throttle.

 

[fenderfuel]

Ok bought a carb kit. It came with some aluminum plugs. How do I get the old ones out? I tried to upload photos but couldnt

 

[interalian]

I drive an awl into the center then pry them out. Others grind a medium screwdriver to a point and drive it in at an angle. Others drill a small hole then drive a screw in and pry it out (I don't like this idea as it would risk getting metal shavings in the carb).

 

[flyingscott]

What do you have the low speed mixture screw set at.

 

[oldboat1]

won't believe you have good spark until you say you measured it with an adjustable tester. You can lie, of course, but it has to be a specific lie (need about a half inch spark, and will likely see more if the ignition is in good shape). I drill out those caps, using a little grease to lessen risk of shavings -- then pull it with a drywall screw. When doing this, I'm also dismantling and soaking everything metal in lacquer thinner (your choice of solvents), including top and bottom halves of the carb -- if aluminum. Then poking ALL openings, and blowing them out with carb cleaner. Not quite sure the idle circuit is the problem in your case, but passages should be cleaned out if you didn't do that.

I'm not sure what the initial idle screw setting is for your model (see flyingscott's post), but think it's probably 1 1/2 open from lightly seated. If you haven't pulled off the domed plug yet, you might first try fine tuning the mix. If it were me, I would try to lean it out (clockwise) from the initial setting -- should get an increase in rpms. Throttle down or adjust the idle stop down (throttle), and continue bumping the needle adjustment clockwise. When you get a lean sneeze, back it out 1/4 turn. I have a sense your current setting might be too rich, and the engine is stumbling when throttling up. Do the link and sync procedure as well, if you haven't done that.