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1998 Johnson 90hp ocean runner - cutting in and out

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  • #1

    1998 Johnson 90hp ocean runner - cutting in and out

    Hi there Johnson forum users,

    New member needs help - motor cutting in and out.

    I have a 1998 Johnson ocean runner 90hp with 315hrs on it. Motor runs excellently when the symptoms below are not present. However; recently I have experienced the following problem:

    Firstly: on the occasion at WOT, the motor cut in and out as if it was starving of fuel. The problem went away after I backed off then went to full throttle again.

    A week later, I had the boat out, all was going well then the symptom was back, once again at full throttle. I backed off then the motor ran fine for a minute, but then started cutting in and out and this time did it at slow speeds as well.
    I repumped the fuel bulb, noticing it had gone soft. The motor still ran poorly and didn't properly recover. When I pushed the throttle for more power I got a rough cutting in and out response from the motor. Limped back to the ramp.
    The motor seemed fine again when I was driving it onto the trailer and had to give it some revs.

    Does this sound like a fuel issue, or possibly a power pack and coils causing a loss of spark intermittently?

    (spark plugs are new, fresh clean fuel, no water in water separator filter, motor inline fuel filter clean, motor was serviced at 305hrs)
    Also what are the symptoms for a failing power pack or coils?
    Last edited by Brett985; 01-11-2015, 08:31 PM.
    Tags: None
  • #2
    update

    Took the boat out today after these jobs:
    Spark plugs replaced with champion Ql78yc
    All filters inspected
    Fuel lines inspected
    Carburettors cleaned
    Power pack and coils unplugged, treated and inspected for corrosion.

    Motor ran fine for an hour then started to hesitate and abruptly cut in and out anywhere above idle.
    Is this power pack and coils playing up?

    Comment

    • #3
      It could be the power pack, but it sounds like something else.

      If you read your owner's manual (You do have an owner's manual, don't you?), you will find your motor has a system built into the module called "S.L.O.W." I forget exactly what it stands for but it is something like "System Limiting Overheat Warning" or something close to that. It is to keep guys from burning up their motors by running them wide open (or trying to) when they are getting too hot. A motor can get hot from a lack of cooling water or from a lean fuel condition (I.e. weak fuel pump or fuel obstruction). Thermostat(s) could be sticking. Temperature sending unit in cylinder head could be bad and sending a false signal to power pack, telling it to go into S.L.O.W. When it goes into SLOW, the motor will not run much above fast idle. If you shove the throttle further forward, the motor will surge and cut back, surge and cut back, rough running because it is in SLOW. If you shut it off and let it cool down a little, it will come out of SLOW and run normally again until it gets hot again. If it is hot, you're going to cook your pistons by keeping on trying to make it go. Read your manual.

      Comment

      • #4
        If you're still chasing your problem, check your ignition switch.
        I had a similar problem on my boat and it turned out to be the ignition switch was making intermittent connection in the "run" position. Thus it was cutting out, making me think it was all sorts of stuff. I spent $600 in parts before I replaced a $35 switch.

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