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Johnson 90 - Where has my top end gone?

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Section - Hi I have a Sea-Ark 18' with a Johnson 90 SPL. The last time I ...
   
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  1. #1
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    Question Johnson 90 - Where has my top end gone?

    Hi

    I have a Sea-Ark 18' with a Johnson 90 SPL. The last time I her it out (about a month or so ago) my son and I noticed that the boat seemed to run fine until you got to about 2/3 throttle but at that point it just died. If you backed off on the throttle just a little, it would run just fine.

    My first thought (and I am not a boat repair person lol) was fuel filter. Seemed like it wasn't getting enough gas to run at the speed we wanted to go. I have looked three times now and can't seem to find a fuel filter.

    Does anyone know if this "could" be our problem, and if so where is the filter located and what does it look like. If not, could it be clogged injectors, and do you think injector cleaner would make a difference or what do you think it most likely is?

    We are putting to boat in the water this afternoon and if anything we can do ahead of time to solve this issue would be great. Thanks

    Doug

  2. #2
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    Not an outboard person here but we have a lot of them on here so someone should chime in. One big question is are you using any ethanol based fuel in it?
    ~ on the hook ~

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    Quote Originally Posted by TimG View Post
    Not an outboard person here but we have a lot of them on here so someone should chime in. One big question is are you using any ethanol based fuel in it?
    Yes on the ethanol based fuel, but it is what I have been using for the past couple years and never had an issue before. Took the boat out again yesterday and same thing, it runs fine up to about 2/3 throttle but above that it just shuts down like I had turned it off.

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    Lt Commander
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    I don't know that particular engine but, from your description, it sounds more like an ignition problem than a fuel problem. If there was a fuel limitation it wouldn't shut off but just wouldn't get any faster. If there was an ignition problem and the spark was cutting out at a certain engine speed then it would just stop.

    It is probably an electronic ignition which means "no user serviceable parts inside" . A good tech with the right testing equipment will find the fault quickly and then probably tell you to replace the whole system.

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    Quote Originally Posted by lotus View Post
    I don't know that particular engine but, from your description, it sounds more like an ignition problem than a fuel problem. If there was a fuel limitation it wouldn't shut off but just wouldn't get any faster. If there was an ignition problem and the spark was cutting out at a certain engine speed then it would just stop.

    It is probably an electronic ignition which means "no user serviceable parts inside" . A good tech with the right testing equipment will find the fault quickly and then probably tell you to replace the whole system.
    Hmmm that does seem to make more sense than a gas issue. Now I need to find someone qualified to work on it.. Thanks

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    Lt Commander
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    Start with your local Johnson dealer. Just telling him/her what happens may get the "Oh, your greeblefitzistor is bawungaed. " If you are a reasonable mechano then just buy another one and install it. Usually, with these "black box" systems, you replace the whole box which is pretty simple to do. It does cost a bit but it should then be fine for either twenty minutes or twenty years.
    TimG likes this.

  7. #7
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    Take a look at your fuel line and primer bulb when its trying to die on ya- I had a pickup screen get plugged once, did exactly what youre explaining and you could see the hose and primer collapse as it started to die. Back off on the throttle, and it ran fine. Just a thought.

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