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Thread: Yamaha problem

  1. #1
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    Yamaha problem

    My buddy has an '89 Yamaha Pro VS 150 and it won't run on all 6. We went fishing today and it was fine until it wasn't. Starting was fine but when he nailed the throttle to get it planing it wouldn't. The last time today it wouldn't plane until he sat in the front seat, he weighs much more than I do. Once it got up I floored it and trimmed it up and it ran the 3 miles back to the ramp OK and loaded OK. It seems like it's missing a couple of cylinders and regains them later. The filter was dirty so we removed it but that didn't help. Anyone know what's wrong. Thanks.

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    It could be a lot of things, for example the stator, and we could shoot a lot of ideas at you, which may or may not be helpful.

    Troubleshooting is required, starting with figuring out whether it is spark or fuel related. Do you know how to do that?
    Markus' Performance Boating Links:
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    It seems to me that if it's not happening all the time it won't be a fuel problem. How do I test for an intermittent problem? Thanks. Squeezing the bulb during the problem doesn't help.

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    How long has he had the boat?
    Are these new symptoms?
    If he has had the boat for a while, how did it perform before compared to now?

    A while back, guy had a boat that sometimes would plane, sometimes the prop would slip too much etc.
    After a little back and forth, turns out guy just bought the boat. Had a prop that used ventilation plugs to tailor rpm for hole shot. He had four empty holes so for under $15 problem solved.

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    One thing to try is finding out what cylinders are missing

    one side, all, two on same carb, ect or just one

    you can use induction tach. Or pull spark and run to see if it affects it.
    '06 Tracker All-Fish/Tournament V-18 90 Optimax, 46.8 gps Goal one complete reach 45 mph.

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    Quote Originally Posted by Motv18 View Post
    One thing to try is finding out what cylinders are missing

    one side, all, two on same carb, ect or just one

    you can use induction tach. Or pull spark and run to see if it affects it.
    Today we checked the temperature on each bank and the starboard one was 195 and the port was 130 before we shut it down. We changed the poppet valve and removed the thermostat, because we didn't have a new one. We also took a compression check, 115 lbs on all cylinders. We ran it, on a hose, for about 10 minutes with the port 120 and the starboard side 90*. All the cylinders were firing. Is it normal shutting down several cylinders when it gets hot? Thanks.

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    It can if the alarm sounds, but heat will interfere with operation even if the alarm isn’t sounding. Might test your buzzer. Don’t have the alarm temp handy.

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    You need to engage in some proper, structured, trouble shooting.

    First, you need to figure out which cylinders are affected. Then you need to figure out if it is spark or fuel related.

    The easiest way to do this is to get a few packs of spark plugs and go out on the water.

    Put in new plugs, run the boat, turn off ignition when the problem happens, take off the cowling and look at the plugs.

    If some plugs are too wet, you have an ignition problem on those cylinders. If some plugs are too dry, you have a fuel problem on those cylinders.

    Then you can start cleaning things, swapping things around, etc, to see if the problem moves or goes away in order to identify what is wrong.
    Markus' Performance Boating Links:
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    Quote Originally Posted by Markus View Post
    You need to engage in some proper, structured, trouble shooting.

    First, you need to figure out which cylinders are affected. Then you need to figure out if it is spark or fuel related.

    The easiest way to do this is to get a few packs of spark plugs and go out on the water.

    Put in new plugs, run the boat, turn off ignition when the problem happens, take off the cowling and look at the plugs.

    If some plugs are too wet, you have an ignition problem on those cylinders. If some plugs are too dry, you have a fuel problem on those cylinders.

    Then you can start cleaning things, swapping things around, etc, to see if the problem moves or goes away in order to identify what is wrong.
    The owner went fishing yesterday with no problem. IMO the problem was heat related on the starboard side. When we removed the thermostat the problem went away. When we took the cover off the it was wide open. Would the poppet valve cause an over heating problem on just one side?

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    If it doesn’t open yep,

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    The thermostat was wide open when we took the housing off but the temperature on that bank was 195. The only thing I can figure is it opened when we took the housing off. It ran 90* after we took it out and the port side ran 120*. He fished all day today and I haven't heard how it ran yet.

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    If the poppet sticks closed when it hits 140-160 the stat will open, but not flow enough to cool it down.

    Sounds like except a new stat your good.

    With working popets its it’s pretty normal for the stat to be closed.

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