99 yamaha 25hp 2 stroke 3 cylinder stuttering

Discussion in 'Outboard Maintenance' started by Lowtidelowlife, Aug 28, 2014.

  1. Lowtidelowlife

    Lowtidelowlife Fine line between recreation and degeneracy.

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    Hey dudes. Been reading through all these posts for the past few weeks. Bought a used j16 with a 25hp yamaha mshx3 and it crushed it on the water test before I bought. Idle, 1/4 throttle, 1/2, 3/4 and WOT.

    Couple days later took it out and was having this issue when I'm coming out of idle and it won't throttle up it'll do this stuttering thing that your reaction is to immediately throttle down. Inspected fuel line and it was pretty nasty, previous owner was running pump gas through her (original owner of skiff and o/b) and it sat for a year (occasional start up on muffs), replace fuel line and all fittings everything clean and snug, cleaned fuel pump and filter, put new plugs in and checked compression, 125 across all three cylinders, unplugged float bowl drain screws and held rag under and shot some carb cleaner inside got some mini pieces of carbon out (can't reach bottom carb without some piece of space age reticulated technology), water tested again and ran like a champion through the whole range of the throttle, but then did the stutter thing after a while and had to idle back to the ramp, did some more rudimentary cleaning out and tested again and had same experience, good running and bad running, except while idling back to ramp I noticed really hot pee (sorry don't know technical name), motor cut out and was hard to start, idled to a nearby dock and let the engine cool off, pulled out of water to see if I picked up a plastic bag or some debris, nothin, idled back to ramp. This is where I stand today. Plan on replacing impeller and thermostat as it won't hurt the motor anyhow, and after some manual readin I read that this model doesn't have an alarm for overheating but does have like a safety mode it goes into if it is overheating and won't throttle past 2000 rpms (I think that's the number) wondering if this stuttering is "safety mode" or another issue. First skiff. First outboard. Been cramming my head with manual reading and forum reading. Would really appreciate any feedback, as I'm on of those broke guys.
     
  2. Lowtidelowlife

    Lowtidelowlife Fine line between recreation and degeneracy.

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  3. cutrunner

    cutrunner Cert. Yamaha technician

    Well, first off your going to need to determine wether you have an overheat issue or a different issue before you can start chasing a problem. Like you said, a service (changing the water pump and thermostat) are a good idea to start.
    ive never put a 25 into safety mode so i cant say what it feels like exactly but if its anything like the other motors it will limit your rpm pretty smoothly. Has the water pump ever been changed?
    Its my opinion that they should be changed every year because they are so small and the blades on the impeller can break off so easily after time.
    also, what prop is on the motor?
     
  4. Lowtidelowlife

    Lowtidelowlife Fine line between recreation and degeneracy.

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    Hey thanks Cut, don't know prop size, what is the safety mode like on the other size outboards? Anyhow changed impeller and thermostat today but since the gear shift rod was really right in the lower unit where you separate it, and getting it free was such a task the plastic piece up top that actuates the shift rod up and down snapped in half. So back to waiting for parts....
     
  5. Lowtidelowlife

    Lowtidelowlife Fine line between recreation and degeneracy.

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    Oh and the impeller was completely trashed. Bits and pieces in the housing and only rockin like 2 or 3 blades left. Mega neglect.
     
  6. Lowtidelowlife

    Lowtidelowlife Fine line between recreation and degeneracy.

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    Put Humpty Dumpty back together again and ran like a top all night last night. What was supposed to be a water test turned into chasing mullet pods and snook till 5 am up and down the county. So best guess was the impeller being so trashed was allowing the engine to overheat which in turn put the engine into safety mode. Last night was first time I've fished 3 people on my skiff with ice and light gear and full livewell couldn't believe the o/b jumped right up on plane. Great little motor. Glad it's sorted out has been a major major dark place for the last few weeks.
     
  7. flyfshrmn82

    flyfshrmn82 Well-Known Member

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    You might want to run some additive in your fuel. Yamaha Ring-Free or Startron are both good. Follow the instructions. Also, make sure you are using a good 2-stroke oil. And don't listen to that 100:1 bologna. Stick with 50:1... I've seen first hand the effects of cheap oil. Last but not least, E-free gas. It's not worth saving 5 dollars here or there (between oil and gas). Your engine will thank you. I killed my Yamaha using the cheap stuff and cheap gas. Cost me over $1500 to repair because I wanted to save a little money (~$200) on oil and gas.
     
  8. Lowtidelowlife

    Lowtidelowlife Fine line between recreation and degeneracy.

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    Fly. Been running some fuel injector cleaner in the tank last couple fill ups, I only use ethanol free (it's only a 6 gallon tank), and run yamalube or quiksilver when I don't have yamalube on hand. Yeah I definitely don't believe the 100:1 deal some dudes say they run it and it's fine, I run 50:1. Thanks for the input though, I wish the previous owner was as good to this outboard as I've been but hey so goes the burden of the crucial dude...
     
  9. Lowtidelowlife

    Lowtidelowlife Fine line between recreation and degeneracy.

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    Fly. Was running on about 45 minutes when I responded to that message. Long night. Will look into that additive you suggested thanks.