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  1. #1
    Member chaseerry's Avatar
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    HPDI Weak Idle But Runs Great

    Hey guys. My 2009 HPDI Series 2 just started this. Starts up perfectly fine. Gets kind of low during first idle but doesn’t die. If I give it any throttle in neutral it dies. If I put it in gear forward or reverse it runs like a champ.

    So tonight after running up the lake a bit I shut down, put it in neutral and could give it gas no problem. After it sits for a while, if I start it and try to give throttle while in neutral it will die.

    I run ethanol free fuel only and Ring Free religiously.

    Any ideas?

  2. Member
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    #2
    Yes I do!
    so your engine in neutral is banging on 4 cylinders. It’s just made that way. As such it’s easy to provide the engine too much fuel and it kills the engine. You have to gently increase the fuel throttling back down so as not to kill it. When you put it in gear it switches to 6 cylinders and voila, you don’t have a problem. Your idle should be set at 800 rpms. If it’s lower you need to increase it.

  3. Member chaseerry's Avatar
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    #3
    Ahh. I have read about the dropping two cylinders but I did not know about the easing into the throttle when in neutral.

    I need to check the idle RPMs then because it just sounds a tad low now. How do I go about adjusting that if needed?

  4. Member MichAngler's Avatar
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    #4
    Check your primer bulb and make sure you can pump it up to the point its almost rock hard

    If its soft and squishy replace
    "The handicapped angler"

  5. Member chaseerry's Avatar
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    #5
    Quote Originally Posted by MichAngler View Post
    Check your primer bulb and make sure you can pump it up to the point its almost rock hard

    If its soft and squishy replace
    Will do!

  6. Member chaseerry's Avatar
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    #6
    I think my Duracell 31 AGM might be the culprit at this point. It seems my voltage gets weak when sitting in idle - I can see it change on my graph and dash gauge. It will go up to around 13 and motor sounds great…then drop to 12 something and the motor gets real slow sounding.

    Bought the battery May 2018. Should they last longer than 4.5 years?

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    #7
    Have battery tested , it may be bad too. My HPDI does same thing at idle in neutral.

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    #8
    Quote Originally Posted by chaseerry View Post
    I think my Duracell 31 AGM might be the culprit at this point. It seems my voltage gets weak when sitting in idle - I can see it change on my graph and dash gauge. It will go up to around 13 and motor sounds great…then drop to 12 something and the motor gets real slow sounding.

    Bought the battery May 2018. Should they last longer than 4.5 years?
    I think you may be seeing a symptom, not the cause. When the motor is running great, it is providing 13V, and when the motor isn't running as well, it isn't charging as well, and you lose that "charge level" voltage.

  9. Member chaseerry's Avatar
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    #9
    Update: New 31 AGM installed. New spark plugs, fuel filter element. A couple of the plugs had a lot of carbon build up.

    Took the boat out today and things are worse. Boat still had that low tone occasionally just idling from ramp to dock to pick up my partner. The more gas I give it the better. Dies when going from reverse to neutral after the dock. Hmm. Fires up again and is fine.

    Turn the key to move to a new spot after an hour. Motor spits and sputters then dies. Uh oh. This is new behavior. Wait a second then crank it up again. Motor idles and then starts sputtering - like it’s starving for fuel. Dies. We go back to fishing thinking the worst. After an hour I go to crank and she sputters and spits again but stays alive barely. I put her in forward and just idle a ways while coughing. Dies. Wait a second and fire it up. This time I give it a little gas for a fast idle in forward and it does NOT sputter. So I fast idle a long ways and get on plane at 40mph. Boat drives great. Set down and boat idles normal.

    This happens a couple more times and we put it on the trailer. What in the world am I in for? Thanks guys.
    Last edited by chaseerry; 08-21-2022 at 10:16 PM.

  10. Member chaseerry's Avatar
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    #10
    Did a compression check this morning just to see. 115-120 on all but #1 (top right if looking at back of motor). It was 65. Not sure what this means…

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    #11
    Check your plugs for fouled ones. These engines are known to foul plugs. I run Techron instead of ring free… it’s the same thing. Your engine idle should be at 800.

  12. Member chaseerry's Avatar
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    #12
    $7,000 for a rebuild (if needed) or $21,000 for a new SHO. Decisions.

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    #13
    Quote Originally Posted by chaseerry View Post
    Did a compression check this morning just to see. 115-120 on all but #1 (top right if looking at back of motor). It was 65. Not sure what this means…
    Compression of 65 psi would indicate an issue with that piston. I would check it again a couple of times to make sure there were no issues with the test. If you are confident that you only have 65 psi in cylinder 1 then you have some issues.

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    #14
    65# compression in that cylinder is not a good sign.

  15. Member chaseerry's Avatar
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    #15
    Okay guys took the head off to have a look before I do something drastic. I can upload more pictures if needed. I was expecting to see damage or something in there like I've seen others post? Thoughts?

    IMG_5044.jpg

    IMG_5045.jpg

    rsz_1img_5050.jpg

  16. Member chaseerry's Avatar
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    #16
    Dropping it off with a Skeeter dealer in town who has a Yamaha Master Tech on staff.

  17. Member chaseerry's Avatar
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    #17
    Okay guys the leakdown tests showed cylinder #1 at 90% and #3 at 45%. Mechanic couldn't tell where the leak was going. Still not sure what caused it still so I'm looking at a HydroTec diagnosis and rebuild. I'm willing to bet it's the locator pin failure like others have had - it just hasn't come loose and caused damage yet.

    Thoughts on a rebuild versus sell the rig and start over? I'm torn.

  18. Member
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    #18
    Such a personal question that no one here can answer for you. If you can find a mechanic to only fix /replace the parts that are worn, re ring it and put new reeds at this point would be your most in expensive route. Where I’m located we only have parts swappers, not mechanics that re build. At that point you could sell the boat with confidence, trade it in, it will take 8 weeks to 6 months to get a new one. Heading into winter is a great time to not have a boat! I was ready to sell my 2000 ranger when it seized up. I was running a 225 on it. The cost was rebuild for about 7 k or for 10k rebuild into a 250. I opted for the later. I felt it would help with re sale and selling a boat with no engine is not very easy. Hind sight I wish I would have shopped around and found a good used engine to put on. I was very surprised how many of those were available in fellow bass heads garages that they had never sold. Prices ranged from 4500 to 6k.

  19. Member chaseerry's Avatar
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    #19
    Mat with HydroTec gave me a good quote after talking with all sorts of shops/dealers. Plus a 1 year warranty and I’ve read numerous good reviews about their service and rebuilds.

    I do have a dealer near me with a 2023 SHO 200HP in stock. $21K to put it on mine. Ouch.

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    #20
    I recall reading another member rebuilt their Yamaha themselves. Need correct tools, time and locate the parts.

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