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  1. #1
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    2004 VMAX Issues

    Engine hesitates at around 65-70 mph, once you let off, it will pick back only to fall on its face again. Changed Fuel/water separator filter, clear bowl filter, VST screen, high pressure filter and spark plugs. All of the basket filters were replaced last year as routine maintenance, nothing looked bad, so I didn't mess with them. My delima now is do I tak it to a shop and if so will they be able to troubleshoot it? Boat runs great at anything under 65 mph. Any suggestions ?

  2. Tony C
    Join Date
    Jan 2007
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    Champlain
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    #2
    Injectors ever been flow tested?
    Ranger Z21/Yamaha HPDI 250

  3. Member
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    #3
    Tonyc,
    I had Brucato flow test the injectors a couple years ago. The motor has maybe had 25 hours put on since then.

  4. Member
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    Sep 2013
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    Southern Kansas
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    #4
    What are your rpm's like when this happens? When My ox66 had o2 sensor troubles mine would run on up just fine then drop about 500 rpm's. If I let out of it for a bit then I could run it up again but it would then cut back 500 rpm's again. Mine was beyond "cleanable."
    1998 Tr-21, 2001 Yamaha 225 OX66

  5. Member
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    #5
    Rat0502,
    To be honest, I'm not exactly sure what the RPM' were, I'd say just above 5000. As long as I let off the throttle, it would run fine at anything below 65 mph. It's a little sketchy running over 70 mph and lose power......turns real hard to the left and if your not ready, it could be really bad!

  6. Member
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    #6
    Quote Originally Posted by Triton77 View Post
    Rat0502,
    To be honest, I'm not exactly sure what the RPM' were, I'd say just above 5000. As long as I let off the throttle, it would run fine at anything below 65 mph. It's a little sketchy running over 70 mph and lose power......turns real hard to the left and if your not ready, it could be really bad!
    That doesn't sound how mine acted, sorry. It would just run up to 5700 or so and then just kind of bog down and drop to around 5200 rpm's. It didn't fall on its face for sure.
    1998 Tr-21, 2001 Yamaha 225 OX66

  7. Member
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    #7
    Thanks rat502!

  8. Member RL552's Avatar
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    #8
    Quote Originally Posted by rat0502 View Post
    That doesn't sound how mine acted, sorry. It would just run up to 5700 or so and then just kind of bog down and drop to around 5200 rpm's. It didn't fall on its face for sure.
    Ths is what my 01 225 ox66 is doing. I put a different o2 sensor on it but haven't tested at wot.

  9. Member
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    Mineola, TX
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    #9
    RL552, be sure to clean the little sniffer tube that is inside the mounting block for your O2 sensor before you run it. If that tube is clogged, the new sensor will not read properly.

  10. Member
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    #10
    Still thinking it could be the lift pumps......See attached.
    Attached Images Attached Images

  11. Banned
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    Jun 2004
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    Apex, NC
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    #11
    No o2 sensor on 3.3L hpdi motor! Looks like fuel pressure is low. Was the YDS data monitored with motor running?

  12. Member
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    #12
    Rich, this was just with the key on.

  13. Banned
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    #13
    Run it on laptop up to the rpm where the problem is occurring.

  14. Member
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    #14
    Thanks Rich! I'll see if I can get the guy that had the software to take a ride.

  15. Member HaulinBass's Avatar
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    Jun 2004
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    Springfield
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    #15
    Pressure on hpdi the same as efi, about 31 psi?
    Larry Eby, 2004 ChampioN 188 Elite/2003 200 Hp Vmax OX66
    "Romans 10:9"

  16. Member
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    #16

    ISSUE RESOLVED

    I was finally able to perform some additional troubleshooting on the hesitation issue I've been having. To make a long story short, it appears a mouse may have got a hold of the fuel line over the winter and put a small hole in the line. I went to pump the primer bulb to check the left pumps and noticed fuel on the line. Once I removed the line running between the Fuel/Water Separator and the engine, the attached picture was what came out of the line. I'm sure all of the varnished fuel didn't help matters at all. I'm vey religious about running Startron fuel stabilizer and Yamaha Ring Free. While I was this deep in the engine, I went ahead and changed the lift pumps, but I disassembled them afterwards and they looked fine. Took the boat for a test run and no issues! 78 mph @ 5900 rpm!
    Thanks again for all the help!
    Attached Images Attached Images

  17. Tony C
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    #17
    Great, glad its running good for you now.
    Ranger Z21/Yamaha HPDI 250

  18. Member HaulinBass's Avatar
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    #18
    That's the junk that I found in the old fuel line too.
    78-sweet
    Larry Eby, 2004 ChampioN 188 Elite/2003 200 Hp Vmax OX66
    "Romans 10:9"