Need help with a Yamaha 90hp 2 stroke

Discussion in 'Outboard Maintenance' started by privateer, Jul 1, 2014.

  1. privateer

    privateer I Love!

    Hope someone can help me out -

    I have a Hewes Redfisher 16 with a 2002 2 stroke Yamaha.

    Runs smooth and clean but lately at wide open throttle (5500 rpm) after a few minutes the engine begins hesitate like its fuel starved. RPMs will drop to 3500 rpm or until I ease up on the throttle. So far it only happens at WOT.

    If I back off right away or keep the rpms under 5000 rpm it doesn't happen.

    I just replaced the fuel filter and water separator and also replaced the primer bulb and fuel line from the water separator to the engine.

    Any ideas?

    Any help would be most appreciated.
  2. DuckNut

    DuckNut Brandon, FL

    Fuel tank vent clear?

    Sounds like you are getting a vacuum in the line.

  3. privateer

    privateer I Love!

    Is the fuel tank vent the same as the overflow?

    If so it is clear.
  4. Godzuki86

    Godzuki86 FlounderPounder

    Have you checked/serviced the poppet/pop-it valve?

    Yamaha calls it a pressure relief valve I believe. Mine was all corroded up with salt and wouldn't open. At idle or low Rpms it was fine but went into limp mode at high rpm.

    I would give that a once over as well.

  5. swaddict

    swaddict Thread Killer

    test your fuel pump, remove it from the engine with the hoses attached and squeeze primer bulb, if fuel leaks on the engine side of fuel pump, the pump is bad, this might be causing your issue, otherwise get a portable tank to see if the you can replicate the issue, if it runs fine, then it's from the tank to engine
  6. cutrunner

    cutrunner Cert. Yamaha technician

    This is your first step
  7. privateer

    privateer I Love!

    Thanks for the advice.

    Will try the portable tank and test my fuel pump this weekend.
  8. privateer

    privateer I Love!

    Replaced the fuel pump.

    Problems Solved.

    Thanks for the advice.
    not2shabby and "Scott" like this.
  9. swampfox

    swampfox 01 Hells Bay Guide.07 ECC LOSTMEN-sold

    Good! Between all the know it alls we have here. I think any issue can be resolved ;)
  10. Jim Lenfest

    Jim Lenfest Well-Known Member

    A common problem with Mercury's and I mention it here because you may be using a Quicksilver hose.....For a few years, they made a hose with a plastic lining. sometimes the plastic lining would separate from the inside of the hose and collapse as fuel was being drawn from the tank. As soon as you stopped or slowed down, it would open back up, to start the process all over again. If you have taken the hose apart for any reason, or are using an old hose, try borrowing one from a friend to see if the problem goes away with a new or different hose. Also as mentioned above, check the fuel pump and high speed jets in the carb. If you are using the small 6 gallon tanks, I usually try to elevate the tank above the engine so fuel gravity feeds. If it runs fine with the tank elevated, replace the diaphragms in the fuel pump as one may be punctured or has stiffened up and not flexing properly to pump fuel.