1988 48hp Evinrude bogging down

Discussion in 'Outboards' started by Brian Polski, Jul 6, 2021.

  1. Brian Polski
    Joined: Jul 2021
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    Location: Minnesota

    Brian Polski Junior Member

    Looking for help on this one because I’m out of answers. I have a 1988 Evinrude 48hp SPL 2-stroke. The motor has never been able to go full throttle without bogging down in some capacity. Motor will run fine wide open for random amounts of time before revving down on its own slowly. Putting back into neutral revving it up full choke fixes it temporarily but it bogs down at again at random times. starts and idles fine once warmed up too. Carbs have been cleaned, spark plugs changed, coils changed, power pack has been changed, fuel pump has been changed. I put sea foam in it occasionally to treat carbs and any moisture in the gas. Pisser flows good water, almost like the motor thinks it’s overheating? Electrical issue?
     
  2. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    For starters, there would be no overheat slowdown on that engine, would there ? I don't think so. I suggest you get someone to sit at the back of the boat and keep on squeezing the primer bulb just enough to keep the fuel pushing through, meanwhile throttle up and see what happens. If it causes the problem to abate, it could mean a number of things, presumably not the fuel pump as you have replaced it, and we might assume no debris in the gauze trap, but a sticking needle valve, or air being sucked into the line is possible. I assume no water in the fuel.
     
  3. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    Ieak in the fuel line to the tank, plugged vent on the tank, fuel line connection at the motor doesn't seal well, etc.

    Pumping the ball and using the choke indicate its running out of fuel. If all the parts have been cleaned or replaced on the motor, then it leaves the fuel line and or tank.
     
  4. Brian Polski
    Joined: Jul 2021
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    Location: Minnesota

    Brian Polski Junior Member

    I have tried a different gas tank and fuel line in the past and that did not fix the problem but that was before new coils and a new power pack. I should also mention an alarm went off at the throttle control one time but it has not done it since we put a bunch of new parts in it. I think it might have been the temperature sensor that time. I will buy a new fuel line and tank to see if that fixes the problem. I’m not sure what the gauze trap is but I will check that. No water in the fuel line as we checked that and replaced the gas. Is the needle valve in the fuel line or at the connection to the motor? Thanks for the help!
     
    Last edited: Jul 7, 2021
  5. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    Needle valve is in the carby, they can get worn and "stick' in the inlet to the carb, and the fuel drops
     
  6. Brian Polski
    Joined: Jul 2021
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    Location: Minnesota

    Brian Polski Junior Member

    Went out today and ran the motor after putting on a new gas tank and fuel line. Engine is still doing the same thing. As soon as I tried to go WOT it bogged down. It did not bog down until I went 100% throttle. Maybe something in the controls? Power pack not responding? Or maybe still in the needle vale? The more I ran it the worse it got it seems.
     
  7. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    Have you employed that test I mentioned, have someone at the back of the boat keep squeezing the primer bulb as you run along ?
     
  8. Brian Polski
    Joined: Jul 2021
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    Location: Minnesota

    Brian Polski Junior Member

    I did, it didnt change anything. We squeezed the fuel line bulb as we were bogging along and no change.
     
  9. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    Money on electrical.

    trigger sensor, cuz you got somethin, but not all of it

    I don't know if there is a running check, but after it bogs down, take the plugs off and look for a wet one; it'd mean that cylinder stopped firing

    if you didn't kit the carb, it could be a worn needle or worn seat, kit it if you don't have a wet plug

    but a new carb after that..no kit, brand new

    hard to advise because I never clean a carb with this type of problem without a new kit

    from a fellow Mn
     
  10. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    Another thought is carboned up bad.

    look up decarb

    also do a compression test
     

  11. Brian Polski
    Joined: Jul 2021
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    Location: Minnesota

    Brian Polski Junior Member

    I brought it to another mechanic and they said it was the floats in the carbs that were not set right. They adjusted them and I will try the boat this weekend.
     
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