Engine Stalling

Discussion in 'Outboard Maintenance' started by redgheenoe, Feb 13, 2011.

  1. redgheenoe

    redgheenoe Well-Known Member

    About 2 trips ago my 15hp Tohatsu 2 stroke which normally runs like a top started too stall at full throttle. It felt like it was getting starved of gas. It would start right back up and run a while and once in a while stall at full throttle again. I ran it 2 weeks ago and the same problem krept back. Fires up..idles fine and at full throttle after about 30 seconds it stalls out. I notice some gas leaking from the primer bulb and I thought my problem was solved. I replaced the primer bulb and started it on the hose. fired up idled for 5 minutes or so no worries. I took it out for a test run today and 30 seconds at full throttle it died. Stared back up and ran in at 1/4 throttle no problem. Any ideas. Please!
  2. Brett

    Brett > PRO STAFF <

    Obtain a second fuel tank and hose, fill with fresh fuel/mix.
    Take it for a test ride.
    If problem solved, you know where to look.
    If problem not solved, it's under the cowling.

    In case you're curious why I started outside the engine
    instead of under the hood, it's because you stated the primer bulb was leaking.
    Usually that's a good indicator of an old fuel line assembly.
    Not only will the bulb get old and leak, so will the fuel line connector seals.
    I always start by checking the easy things before pulling the outboard apart.


  3. joshuabward

    joshuabward I want to go FAST!!!

    Best guess is that the jet is plugged from what you described. When you open the throttle the airflow is increased and fuel flow is increased to maximum flow of the jet. The jet is essentially a fuel flow metering device. If it is partially plugged which is what it sounds like to me, then running it WOT will lean it out and possibly blow it up. To be safe I would pull the carb and clean it. It is very simple design I have done it on the 9.9 version (virtually identical) a few times.
  4. redgheenoe

    redgheenoe Well-Known Member

    picked up a new fuel line and will try it out this weekend. When I described the problem to the shop that sells the fuel line they mentioned it could be a failing fuel pump bladder. Any thoughts?
  5. redgheenoe

    redgheenoe Well-Known Member

    anyone...fuel pump bladder...
  6. Brett

    Brett > PRO STAFF <

    Look at the parts diagram for your Tohatsu.
    In the exploded diagram of the carburetor is the fuel pump assembly.
    Fuel pump is driven by pressure changes in the crank case.
    Part numbers 1-20 are one way valves.
    Part number 1-23 is the pump diaphragm.
    The small valves and the pump diaphragm are composed of a neoprene-like material.
    As they age they get brittle, lose flexibilty and start to crack and leak.
    Just like your primer bulb on the fuel line.
  7. redgheenoe

    redgheenoe Well-Known Member


    I purchased a new fuel line with tohatsu connectors.  I had a spare 6 gallon tank.  Took it out today and it ran flawlessly.  Thank you for the advice.   
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