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  1. #1
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    Johnson 90 hp won't accelerate

    Ok guys, I'm about ready to cry uncle on this one! The motor is a 2000 Johnson 60* V4 looper (model PLSSE). It's on a 22' Lowe pontoon. Customer had it at another shop for months before I got it. My wife suggested that they bring it to me...



    They complained that the engine would not stay running and that when it did it would not accelerate. Also that they had spent untold amounts of money with the other shop and that they just wanted it to run...

    The first thing I noticed was that the key switch was loose in the binnacle. Loose as in spinning around when you tried to crank the motor. When I removed the plastic cover the switch literally fell apart and the wiring harness was twisted tight. Also the float bowls on the carbs were cracked and leaking to the extent that the primer bulb would not get hard.

    I ordered a new key switch, carb kits, and float bowls. Also a new water pump kit at the customer's request. After replacing the ignition switch, water pump and rebuilding the carbs the troubleshooting began...

    Let me first say that I am using CDI's troubleshooting guide here. Also the VRO was deleted by removing the oil tank and lines and unplugging the wires.

    The motor idled well and performed fine at slow speeds, accelerating beyond about 2500 rpms brought on a dead miss and shaking of the engine.

    Mashing the key switch (choke) floods and stalls the engine.

    I drained some fuel out of the tank into a mason jar and there was no water present. There wasn't much fuel left in there so I grabbed a known good 3 gallon can with hose and primer bulb and hooked that up once what was in the tank was depleted. No change.

    Compression check revealed all 4 holes are within 3 psi of each other (125 avg IIRC).

    I tested the temperature switches, ran with them disconnected, rerouted the tan wires as far away from the spark plug wires as possible, verified that quickstart was working as intended. New spark plugs (Champion QL78YC gapped at .030") were installed.

    I unplugged the yellow wires from the rectifier and got no change.

    I checked for voltage on the yellow/red wire to the power pack while running and found none. No difference with this wire disconnected in fact (it supplies 12v to the optical sensor while cranking as cranking speed may not supply enough voltage to result in spark).

    It seemed that the power pack was stuck in "S.L.O.W." mode. CDI recommended at this point to replace the power pack. I went ahead and got the kit which included the optical sensor and plug wires. I found it odd that the pack says on it to use the Champion plugs and the gray plug wires but the wires in the kit were blue.

    At this time I also verified the timing pointer with a dial indicator (it was off about 4*) and set the timing using a tool similar to the factory one (Johnnyrude Fastrike-Intruder V4-V6 Easy Timer) and did a lync and sync.

    Now the engine accelerates smoothly but just seems to bog when trying to get up on plane. I verified the timing while hanging off the back of the boat and that all cylinders are firing in the correct order. I have done a spark gap test (no problem jumping a 7/16" gap), checked the primary and secondary ignition rpms with an inductive tach (all are the same). I went back to the gray OMC plug wires. No change.

    I questioned the fellow who built the timing tool I got (a retired OMC tech) and he offered a few suggestions. He said that there was a clear plastic sleeve on the roller that actuates the carbs that frequently cracks and falls off. I found this to be missing. I replaced it and - no change (I went through the whole lync and sync procedure including verifying the timing pointer at this point).

    He also offered that the bearing carrier in the lower unit could be upside-down with the anode blocking the exhaust exit. This does not seem to be the case.

    Prop is a stainless Solas 13-3/4"-13p which is the same prop recommended by the prop calculator for this combo, gotta be in the ballpark there.

    I noticed that there were open connections at the fuel pump for the VRO, I plugged these as I thought it might be sucking air in lieu of oil. No change. I have installed a VRO delete fuel pump kit that eliminates the VRO section of the pump completely. I have cleaned the fuel filter (it looked pretty new and not very dirty, I back flushed it and reinstalled).

    I am at a loss here. Every check that I do seems okay. I must be missing something simple!



    Any ideas?

  2. #2
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    reeds all there? No mouse stuck in a bad way?

  3. #3
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    No sign of any rodents...

  4. #4
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    Water intrusion when getting hot, not sucking air from anywhere? What's left, tuna fell off, sucking exhaust with cowl on?
    Grab the plug wires under load to confirm no leakage!
    Last edited by FMP; 08-16-2018 at 01:03 PM.

  5. #5
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    I've cut it off under load and pulled the plugs, no sign of water. Reeds pass the "flashlight test." It runs the same with cowl on or off, I had the lower off to change the water pump, didn't notice anything unusual in the mid. I haven't started yanking plug wires under load but it runs smooth. Before I changed the pack it shook really bad with the dead miss on one bank.

    I tore the stator out this morning, it does have the potting starting to melt off, but it tested good. Maybe just keep throwing money at it...

  6. #6
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    I'm not reading all that again, could a coil be breaking down? Stator?

  7. #7
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    Is it making any kind of weird exhaust note when trying to accelerate. We had a 60hp Yamaha on a pontoon that kicked our a$$ for a bit. Popped the power head and found the exhaust almost totally plugged. Just a thought.

    1983 hydrostream viper
    150 merc

  8. #8
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    did you try disconnecting the shift swicth? a tight shift cable or shift rod canactivate it cutting off a couple cylinders
    "One of the penalties for refusing to participate in politics is that you end up being governed by your inferiors". Plato .

  9. #9
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    I think I found it. I'm ashamed to say what it was though...

  10. #10
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    Forgot the anchor, untie from the dock?

  11. Likes Merc 2.5 liked this post
  12. #11
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    you put diesel in it?
    "One of the penalties for refusing to participate in politics is that you end up being governed by your inferiors". Plato .

  13. #12
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    you were using the warm up lever as the throttle?
    "One of the penalties for refusing to participate in politics is that you end up being governed by your inferiors". Plato .

  14. Likes FMP, Merc 2.5 liked this post
  15. #13
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    Forgot to unstrap from trailer

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  17. #14
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    pontoons full of water
    "One of the penalties for refusing to participate in politics is that you end up being governed by your inferiors". Plato .

  18. #15
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    Mounted engine on bow

  19. Likes Merc 2.5 liked this post
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