15 johnson idles fine and but bogs at WOT

Hi guys. I have been reading the forums for a couple weeks and has just been too lazy to register. i have learned so much already. well to the problem. i have a 1985 johnson 15hp. it will start on the first or second pull idle for days, then when i put it in drive it will bog down till i play with the choke and i can find a sweet spot for it to run at about 3/4 throttle. it will go full throttle perfectly then die after about 150 yard of WOT running. if anybody can help me out id really appreciate it. thanks in advance

I would say the carb needs to be cleaned out. It's not a big job on those motors. I use to have an 1983 9.9 evinrude. Had the same problem with my 40 when a main jet got some junk in it. It would start and idle fine then when you gave it the gas it would fall on it's face right before it planed out it. Once I cleaned it out it run fine. That's my best guess. Hope this helps some.

Most likely its your carb that needs cleaning. But check your pump ball to insure it works, check the gas line from the tank to the engine. Check the fuel filter. Make sure the vent on the gas tank is open all the way and isn't clogged.

I've replace the spark full and the fuel line. I run 93 octane in it. I've removed the carb and ran a healthy does of cab cleaner(about a can and a half). Now the needle on the front of the motor is the slow speed adjustment I think. When I removed it to take off the airbox I haven't went trough the adjustment process yet.I don't know if that has somthing to do with it or not. But I cam keep it running at idle and 3/4 if i play with the choke. I think I'm gonna take the carb off tonight and set it in and let it soak. What is a good solution to soak it in.

Remove the carb and soak in a good carb cleaner. Go to a dealer and get a carb kit for it or if you have to get one from Napa (aftermarket). Always have your model number handy when ordering parts. Do not try and continue to run the engine at high RPM with a lean condition or your next issue will be a seized piston. Fix the carb! Another tip, no need to run any higher octane in a production outboard than 89 octane. You will actually build more (and more sustainable) HP with 89 than 93 as it will take better advantage of the two stroke spark curve. Good luck with your repair.

Carb kit and good cleaning!!!!should take care of it!!!

There could be another problem other than carb.Fuel pump.A weak fuel pump will give you the problems you are having.If you haven't taken carb off yet try squeezing primer bulb when motor is running to see if its hard.If not could be a pump problem.

bubba3689 said:

I've replace the spark full and the fuel line. I run 93 octane in it. I've removed the carb and ran a healthy does of cab cleaner(about a can and a half). Now the needle on the front of the motor is the slow speed adjustment I think. When I removed it to take off the airbox I haven't went trough the adjustment process yet.I don't know if that has somthing to do with it or not. But I cam keep it running at idle and 3/4 if i play with the choke. I think I'm gonna take the carb off tonight and set it in and let it soak. What is a good solution to soak it in.

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I think your on the right track starting with the carb, but do not soak it in carb cleaner, the outboard carbs are coated with a protective coating to help keep them from coroding and if you soak them you will strip it right off. A can of carb cleaner will do just fine.

One more thing, don't run high octane gas, the regular unleaded is perfect for these engines.

Bufford

Clean out the carb. I had the same problem with my motor last summer.

Thanks for all the replies. So when its running the primer bulb is supposed to be hard or soft. I got some new fuel line today and got a piece of clear so I could see the gas. Figured it might help me see if there air getting in or fuel stopping.

bubba3689 said:

Now the needle on the front of the motor is the slow speed adjustment I think. When I removed it to take off the airbox I haven't went trough the adjustment process yet.I don't know if that has somthing to do with it or not.

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Yes it is the slow speed mixture. It should be about 1 1/2 turns out.

Your primer won't be hard but shouldn't take much to pump back up. (less than a pump)

The primer bulb will be soft. Remember that the fuel is being pulled or sucked through it.

Not to insult anyone by stating the obvious but is the vent on the gas can open? if the vent is closed the engine will run until a vacuum is created in the tank and will cause the engine to starve for fuel. Like I said not trying to belittle by starting at square one but everyone's been new at one time.

Crankworm said:

Not to insult anyone by stating the obvious but is the vent on the gas can open? if the vent is closed the engine will run until a vacuum is created in the tank and will cause the engine to starve for fuel. Like I said not trying to belittle by starting at square one but everyone's been new at one time.

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Probably not a bad pump or a vent issue as the engine can be made to pick up if he plays with the choke. That indicates that there is plenty of fuel in the bowl to run on. Plus, if the vent were closed, eventually the bulb would go flat and he would pick up on that hopefully. Good helpful comment though!

well i rebuilt the carb and had the fuel pump rebuilt. i got a new recoil starter spring because mine broke and i cant figure out how to get it on ive tried about 10 different ways

Well I finally got it on and primes the motor and it started right up. I set the idle and let it idle for about 10 mins and revved it up and it did fine. Put it in drive and opend it up for a second and was fine. Imma give it a test on the water tomarrow thanks guys