yamaha 25hp problem

Discussion in 'Outboard Maintenance' started by txtroutfisher, Jul 29, 2015.

  1. txtroutfisher

    txtroutfisher I Love microskiff.com!

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    I have a 2002 yamaha 25hp 2 stroke 3 cylinder 
    Here's what's going on
    I run the boat about 10 min to my fishing spot and turn motor off Runs good . Start motor again and probably run for 3-5 min and then it boggs down feels like it's dropping a cylinder. Sometimes I can turn motor off and back on then it will run a little longer before it happens again.  thoughts?

    Carbs have been rebuilt
    New tank, lines and connectors
    Compression is 150 on all 3
    Plugs are not wet 
    Not overheating
    I use 100/1 ratio
    Help please.  Thanks in advance 
     
  2. RunningOnEmpty

    RunningOnEmpty I Love microskiff.com!

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    I have the same motor and it had a very small hole in the fuel pump diaphragm and it caused the same type of problems. It ran good at idle, but it wasn't getting enough fuel and it would fall on it's face under load.
     

  3. txtroutfisher

    txtroutfisher I Love microskiff.com!

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    Thanks for replying I have pulled the cover off the fuel pump and there was some gunk in it so I cleaned the best I could but I couldn't take the whole pump off the carb. How do you take it off?
     
  4. RunningOnEmpty

    RunningOnEmpty I Love microskiff.com!

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    It's a part of the carb float bowl. The black plastic center piece is all you need to work on. http://www.boats.net/parts/search/Yamaha/Outboard/2002/25MSH3A/CARBURETOR/parts.html
     
  5. txtroutfisher

    txtroutfisher I Love microskiff.com!

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    Thanks I will look into it. I'm curious what oil ratio do you use?
     
  6. anytide

    anytide Administrator Staff Member

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    make sure fuel tank is vented right.

    :-?
     
  7. txtroutfisher

    txtroutfisher I Love microskiff.com!

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  8. Sandalous

    Sandalous Well-Known Member

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    Check your fuel bulb. I had the same exact issue every once in a while with my 60, could not figure it out for the life of me, did everything I could think of, and sold it with the issue. I contacted the new owner a few months later and he said that simply changing the fuel bulb solved the problem.
     
  9. RunningOnEmpty

    RunningOnEmpty I Love microskiff.com!

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    Does it continue to run after the problem shows up? Maybe it's going into limp mode? Are all of the cdi connections clean? My 30hp had a few that were corroded really bad including the ground when I bought it.
     
  10. txtroutfisher

    txtroutfisher I Love microskiff.com!

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  11. txtroutfisher

    txtroutfisher I Love microskiff.com!

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    Yes still runs when problem starts. All connectors are clean. This motor is driving me nuts
     
  12. RunningOnEmpty

    RunningOnEmpty I Love microskiff.com!

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    If your 100% sure that the carbs, fuel pump are good than I would start trouble shooting the ignition. I did manage to foul a plug on mine from idling a bunch and it caused the motor to act up. I thought the carbs were dirty for sure so I rebuilt them and all three looked perfect. $11 for three new NGK plugs did the trick.
     
  13. txtroutfisher

    txtroutfisher I Love microskiff.com!

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    Had the carbs professional done getting rebuild kit for fuel pump tomorrow. New plugs. I think it's either the coils or power pack
     
  14. anytide

    anytide Administrator Staff Member

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    yes its 13 years old.... start replacing parts.

    when my 1998 mariner started acting wierd this is what i did.
    coils / stator / trigger / plugs / wires / etc.
    these parts get brittle / burnt
    heat / vibration will make things change (elect) after warmup.
     
  15. Gramps

    Gramps Living & Dying in 3/4 Time

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    Probably a coil or stator. When they get old, cranky, worn, and hot, they start to short out.

    Where is Brett? He can explain this much better than I!
     
  16. Dadvocate

    Dadvocate If it ain't broke tweak it a little....

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    Make sure all bolts in your throttle linkage on starboard side of motor are tight. When I purchased a used 2006 25hp I went thru carbs, installed new plugs, cleaned fuel filter and installed new Yamaha fuel line assembly that terminated into tank with a brass 90 fitting and hose clamp. Ran awesome for a couple months then developed a similar problem to yours. I had the bolt that goes through the accelerator arm loosen. The motor would rev up in gear get on plane and the bog way down. Wait a couple minutes the back to WOT then bog down. Looked motor over real good and found loose bolt. Cleaned and reinstalled with Blue loctitie. Maybe not your same problem but would not hurt to look.
     
  17. txtroutfisher

    txtroutfisher I Love microskiff.com!

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    Thank you all that replied . I went through the fuel pump again and found a small hole in diaphragm. Installed a new one and gasket. I have taken it out twice since then and the motor runs good so far thanks again
     
  18. anytide

    anytide Administrator Staff Member

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    good job !

    [smiley=1-thumbsup3.gif]
     
  19. RunningOnEmpty

    RunningOnEmpty I Love microskiff.com!

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    Sweet! Keep an eye on the thermostat. Mine had all kinds of trash caught up in it. I check it often now. I used grease on the thermostat housing gasket to prevent it from sticking so that I can re use it. It seals just fine.
     
  20. Jigmaster

    Jigmaster Member

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    Don't discount a dirty/ clogged fuel pick in the tank itself.