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  1. #1

    Default 1993 Johnson-After rough idle, squeezing the Primer bulb hard until I feel a release, then runs fine

    I have 1993 Johnson 115 VRO. Its been temperamental lately and goes from running great to running terrible with no warning when it will go south. I have already inspected all fuel lines, filters and valves from the tank to the motor and I am also doing my testing using a 6 gallon portable tank. I have also pulled the carbs and cleaned then very good. Compression is 118-130 in all cylinders.

    Basically the boat starts and runs fine 80% of the time from Idle to WOT. Occasionally (and usually at the least opportune time) it will run very rouge at idle and keep stalling out with gasps and snorts and won't even go into gear (fast idle is fine).

    One thing I realized recently is that if I squeeze the primer bulb when its having a fit at idle, it runs better, and if I squeeze the bulb very hard, I will feel something "give" and then suddenly it starts to run good again. Its like when I squeeze the bulb hard it releases some restriction somewhere and then starts working again. Its never had this problem at high RPMs, its always low RPMs.

    I've used multiple tanks and multiple fuel lines and bypassed the F/W separator. My current theory is its the VRO pump, but I wanted to throw it out there to the group before I waste $350. My theory is that there is something wrong with either the fuel side diaphragm or the the spring or the pump shaft and it "sticks" at low RMPs. When its rev'd up, there is enough force to overcome the problem.

    The only hole in this theory is that it always runs fine at high RPMs and is very inconsistent.... I would think a Fuel Pump issue would be more black and white and it would be a problem at high RPMs too. Can anyone else think of something on the engine side that would "give" if you squeezed the primer bulb really hard and open up fuel flow? Maybe some valve or something? Let me know if you think I should look anywhere else before ordering a new VRO pump.
    thanks.

  2. #2
    Join Date
    Sep 2010
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    Default Re: 1993 Johnson-After rough idle, squeezing the Primer bulb hard until I feel a release, then runs

    First off there is no need to run out and buy a complete new pump.--Repair kits are available / cheap and easy to install too.---Do a spark check and see if you have an ignition system issue.----------Spark must be able to jump a gap of 7/16" on all 4 to be considered to be in good health.---The low compression in one cylinder may be an issue, and if it is a " crossflow engine " you might want to pull that bypass cover to inspect the piston and rings.-----------Costs but a small gasket at say $1.19 and also easy to do.

  3. #3

    Default Re: 1993 Johnson-After rough idle, squeezing the Primer bulb hard until I feel a release, then runs

    just my 2 cents, but I've had the valve in a primer bulb occasionally get stuck and give me fits , similar to what you're describing. It was on a bass boat W/ a 200 hp

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