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  1. #1
    Member B Robinson's Avatar
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    2002 Yamaha HPDI spark plugs, power loss, questions, etc

    My HPDI has been running rough, and has not been hitting on all cylinders, I don't believe. I ran the diagnostics on it Sunday, and all coils are operating, as well as the injectors. My plugs could stand to be changed, so I guess I'll be doing that. Biggest question is, I've always run NGK BKR7EKU plugs in this motor. Do I, or should I, go with something other than NGK? These plugs aren't even a year old, and I don't make long runs. Just seems to go thru these plugs more often than you'd think. I've had problems finding a cross reference chart online, but also want to make sure I'm running the same plugs. What exactly are the plug needs and specifications for this motor?

    Also, while all plugs were out, I did a compression test. Lowest was 85, highest was just over 100. I think I'm ok and within boundaries, but know that's pushing it some. Trying to push the boat up on the trailer has been a struggle lately, as it just bogs down. We'll start with the plugs, then I'm not real sure where to go. But it def needs something. Thanks for all considerations.
    2002 Lund ProV 2025 Magnum /Yamaha 200 HPDI

  2. Member B Robinson's Avatar
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    #2
    Nothin. Ok....well I'm watching some videos, guess I'm gonna look at the neutral switch, make sure all 6 cylinders are firing, and then look at cleaning the 02 sensor, and some filters. Put a new set of plugs in, no dice.
    2002 Lund ProV 2025 Magnum /Yamaha 200 HPDI

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    #3
    I never ran anything but the NGK plugs, but had to keep them changed. I don’t know the specified compression off hand, but your numbers have a greater than 10% difference which isn’t good. We’re the compression numbers closer together on the other five?

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    #4
    I had issues with both my neutral switch and my shift switch this spring. If you have the YDS, then you should be able to see both the switches' status. The neutral switch should always be on when starting motor, and then off when shifted. The shift cut switch should always be off anytime you are not in the water. It really only actuates during "high torque shifting events," or like when putting in reverse while moving forward at the ramp etc.

    One of the things that got me, is if the neutral switch is off when the motor is started, then the motor will keep itself in limp mode, even if you get the switch operating. Restarting the motor will clear this up.

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    #5
    I've seen many of these engines have a blown head gasket with those compression numbers. Do a leak down test on it. Also need to send injectors to be cleaned and calibrated.

  6. Member B Robinson's Avatar
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    #6
    Ya, the compression numbers were a bit tighter on the other 5. And the numbers are higher if I take one plug out at a time. I'll probably do that again, just to see what they are again since it's been a little while since I have.
    2002 Lund ProV 2025 Magnum /Yamaha 200 HPDI

  7. Member B Robinson's Avatar
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    #7
    I don't know if I've ever run the YDS while the motor is running, so I'm going to try to get that done sometime just to see what else it'll tell me. I've done so much work on this motor....I'm getting tired of it, that's for sure.
    2002 Lund ProV 2025 Magnum /Yamaha 200 HPDI

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    #8
    do a decarb job on the motor before changing plugs. I have seen this completely resolve the issue you are speaking of on a HPDI.

  9. Member B Robinson's Avatar
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    #9
    What exactly is a decarb job?
    2002 Lund ProV 2025 Magnum /Yamaha 200 HPDI

  10. Member B Robinson's Avatar
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    #10
    Hoping to find out more about this decarb job. I know one job that's getting done....took out the 02 sensor, and eeesh...shoulda been done a while ago it looks like. Chunks of black goo fell out, it's pretty rough, so I'm gonna clean it up best I can. Haven't seen the sensor itself yet, but I'm guessing it won't be pretty. I'll post some pics later.
    2002 Lund ProV 2025 Magnum /Yamaha 200 HPDI

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    #11
    There are a lot of threads with decarb specifics, but it is basically running a really high load in of Ring Free for a few gallons. That will get the carbon buildup off the internals of your engine. Then you change the spark plugs and away you go.

  12. Member B Robinson's Avatar
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    #12
    0812200124.jpgI may look into doing that. My cousin tells me the Quicksilver gas treatment is the best he's ever seen as well. Here is the pic of the O2 sensor mess. This doesn't show the massive amount of black that fell out as I took pieces out, too. I soaked these pieces in carb cleaner for a few days, more stuff fell out. Soaked the sensor itself, sprayed it out pretty well. It didn't look near as dirty as the other pieces. I'm currently into the back of the motor, have the fuel rails off, replacing the tiny injector filters, cleaning that all out as well. If the motor doesn't run better after all this work, then the disappointed will be monumental.
    2002 Lund ProV 2025 Magnum /Yamaha 200 HPDI

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    #13
    Did my o2 sensor service after 280 hours and it was the same as yours. Lower compression.... is it on the bottom left cylinder as you're looking at the motor from the back? Mine is lower in that cylinder also. I run ring free and non ethanol fuel and pennzoil xlf oil. Ngk plugs every 100 hours or so.
    More than likely a fuel issue due to bad filter. One thread mentioned a cracked filter holder allowing the motor to get air not fuel when under load.
    Nick McDaniel

  14. Member B Robinson's Avatar
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    #14
    The cylinder I had problems with was #4, middle starboard side cylinder. I just installed new mystery filters in the injectors, the pump above them, and am also going to look at my neutral switch to make sure all 6 cylinders are running. Then I'll take it out and see what happens. Going to run a heavy dose of fuel treatment thru it as well, and hopefully all of this will make a difference. If it doesn't, you might hear me scream if you're standing outside.
    2002 Lund ProV 2025 Magnum /Yamaha 200 HPDI

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    #15
    Have you changed all your your filters? Get a mason jar and pull the gas line in the motor at the joint before it fills your cup/filter canister, using your bulb, pump some gas into the jar. Let it sit an hour or so and see if there is any water separation and if you have any black specs in your gas from hoses breaking down. I've seen and heard of this several times. Especially on older boats, condensation in the tanks build up, especially for those that keep they're boats outside all the time. If you see a layer of separation you need to empty your tank,treat it and fill with fresh gas. I would also replace your gas lines from the tank to your filter canister, older gas lines break down and particulates can cause lots of problems. A friend of mine spent a lot of money on his motor before anyone ever checked the gas, once he cleaned his tank and filled with fresh gas it ran like a champ.
    Last edited by baarw; 08-31-2020 at 02:44 PM.

  16. Member B Robinson's Avatar
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    #16
    That's a good idea letting the gas sit. I believe I'll do that tomorrow. I did change the fuel filter/separator which I have a lot of faith in keeping things clean. Most of the mystery filters in the injectors looked pretty good. I haven't changed the other filter in the see thru longer cup on the port side, but I may do that soon. I plan on taking apart the VST this winter and giving it a good cleaning since I watched a video on it. Looking forward to tomorrow to see if what I've done so far makes any difference.
    2002 Lund ProV 2025 Magnum /Yamaha 200 HPDI

  17. Member Ranger519VS's Avatar
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    #17
    When I had an HPDI it went through sparkplugs pretty quickly. I was always on top of the maintenance but plugs just didn't last that long. Did have a problem with the motor losing rpm while getting on plane and it turned out it was the strainer screen on the bottom of the electric pump inside the VST. It was almost completely plugged with fine particles. Never did figure out where they could have come from as there was 2 filters ahead of that one and at least 2 filters downstream.

    BTW, none of those problems with my SHO.
    Butch Derickson
    2011 Z521 w/250 hp SHO
    Traverse City, Michigan

  18. Member B Robinson's Avatar
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    #18
    Aright, here's what we learned today on the motor....the neutral switch is working, as all 6 coils were firing. Took the spark plug wires off while it was running in gear, you could hear the difference. All did this....except cylinder 3, which is the middle one on the starboard side, the one I lost the piston in last year. (I may have said #4 earlier, but it is the #3 cylinder) I suspect the #3 cylinder has not been burning fuel for some time. The park plug is firing as we saw it outside the cylinder as it was running. So, at this point, I'd say I either have a bad injector that's not giving it any fuel, or something is going on internally, or....I need to replace the head. When the head was taken off last year, I remember seeing the inside of it was pretty beat up. With metal pinging around in there for a short time, it's definitely not smooth like the others. So, do you think that fuel is not burning in there because it doesn't have nice smooth area for the explosion to happen like in the other cylinders? Do you think if I install another head, it'll start burning fuel? With that being said, how do I know if the injector is shooting fuel into the cylinder? With the metal pinging around in there, maybe it took out the injector? I remember the guy saying it was fine, looked good when he put it back together, so I just took his word for it. Didn't really question much as I didn't know nearly as much then as I do know about all this. Looking forward to your thoughts on the head and/or injector issue. Thanks--
    2002 Lund ProV 2025 Magnum /Yamaha 200 HPDI

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    #19
    I would do a leak down test. especially on #3. The dings in the combustion chamber could cause hot spots/detonation which is not good, but it just depends on how bad they are. Leak down will tell you if you have a sealing issue/ring or piston problem in that cylinder.

    Wayne

  20. Member Ranger519VS's Avatar
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    #20
    Quote Originally Posted by B Robinson View Post
    Aright, here's what we learned today on the motor....the neutral switch is working, as all 6 coils were firing. Took the spark plug wires off while it was running in gear, you could hear the difference. All did this....except cylinder 3, which is the middle one on the starboard side, the one I lost the piston in last year. (I may have said #4 earlier, but it is the #3 cylinder) I suspect the #3 cylinder has not been burning fuel for some time. The park plug is firing as we saw it outside the cylinder as it was running. So, at this point, I'd say I either have a bad injector that's not giving it any fuel, or something is going on internally, or....I need to replace the head. When the head was taken off last year, I remember seeing the inside of it was pretty beat up. With metal pinging around in there for a short time, it's definitely not smooth like the others. So, do you think that fuel is not burning in there because it doesn't have nice smooth area for the explosion to happen like in the other cylinders? Do you think if I install another head, it'll start burning fuel? With that being said, how do I know if the injector is shooting fuel into the cylinder? With the metal pinging around in there, maybe it took out the injector? I remember the guy saying it was fine, looked good when he put it back together, so I just took his word for it. Didn't really question much as I didn't know nearly as much then as I do know about all this. Looking forward to your thoughts on the head and/or injector issue. Thanks--
    Should have sent the injectors out for cleaning an re calibration when you did the rebuild. Still not too late.
    Butch Derickson
    2011 Z521 w/250 hp SHO
    Traverse City, Michigan

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