2002 70hp Yamaha cutting down full throttle

Discussion in 'Bubba's Outboards' started by NIMROD, Aug 28, 2007.

  1. NIMROD

    NIMROD New Member

    Messages:
    175
    State:
    Arkansas
    I start out and motor runs fine . Go several hundred yards full throttle and it drops to running like it's running on one cyclinder or jumps (cuts out). I can kill motor and restart it runs fine till you open it up and run a short distance. Sometimes it will run 1/2 throttle with no problem for several minutes. It's mainly on top end that causes the motor to cut down. But runs fine to kill and restart ? Could this be caused by fuel or by spark from electrical system ?
     
  2. Cathooker

    Cathooker New Member

    Messages:
    299
    State:
    Ga
    I had a problem similar to that and it was a carburator that needed rebuilt.
     

  3. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    That motor is primer injected ain't it. No choke. If it has a choke the try choking it to see if it picks up.
    An old trick I use and learned a long time ago is this.
    Take the air silencer off and take it out on the water, This requires two persons, When you open it up and it tries to fall take two fingers and stick them in the mouth of the carb and if it picks up and runs then that is the carb that needs the attention.
     
  4. Bigjonrigger

    Bigjonrigger New Member

    Messages:
    16
    State:
    Missouri
    May be a fuel supply problem. When it starts to miss squeeze the primer bulb and see if it comes back to life. If not, its probably a dirty carb.
     
  5. NIMROD

    NIMROD New Member

    Messages:
    175
    State:
    Arkansas
    Thanks , I believe my problem was the fuel line. I replaced plugs , ran seafoam in the gas. Checked the fuel filter in the settling bowl.It would cut down mostly at full throttle. Checked fittings and bulb was still rock hard. I took loose and reconnected the line and suspect the line by the bulb was kinked. When high demand for fuel as full throttle it collapsed the line shutting off the fuel. The fuel line is run under the rear deck out of sight. Hope this is all fixed now . Thanks for your input.
     
  6. crusinman2002

    crusinman2002 New Member

    Messages:
    374
    State:
    Mukwonago, Wisconsin
    another thing that would cause it, it happened to me, is water in the fuel. my vent is right in the area where water comes over the rear deck if you stop quickly or back up too quickly, and i had gotten water in the tank from the vent. i installed a water seperater filter (just over $25 from gander mountian) and haven't had a problem yet. replacement filters are only 5 or 6 bucks. ***don't get the one from walmart as it doesn't come with fuel line fittings*** the one at gander mountain comes with the fittings, i don't know bout elsewhere. all u got to do to install it is find a location where your fuel line runs to mount the base, but u need clearance for the filter under it. cut your fuel line so that the primer bulb is before the filter. there are flow arrows on the base, put your fittings in so that the fuel will flow with the arrows, and then plug the other 2 holes. install your fuel line onto the 2 fittings and then install the filter, it goes on and off just like an oil filter, then prime it and your ready to run water free gas to your engine. you just have to make sure to change your filter out every now and again as it accumulates the water inside of it and holds it there.