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Discussion Starter #1
Hey folks,
I was wondering if any of you know enough about little Yamaha 2 strokes to answer this question. I have a 2001 9.9 hp, and was running near full throttle last week when the motor just stopped. No sputtering, no rough running ... went from nearly open throttle, little boat up on a plane, to shut off (damned near threw me from the boat). Wouldn't start afterward. Not even a chug.

Ran the electric and paddled the 3.5 miles back to the house. Started on the first pull back at the house and idled just fine. Started and idled just fine when I removed it and prepped it for storage.

Does anybody know if there is a overheat-kill feature on this motor? I was talking with somebody afterward and they made it sound like the motor would shut off if the engine got too hot, but I don't recall having read about that in the manual.

Any thoughts? Any input is welcome. Thanks.

Best regards,
Dogwood
 

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Disclaimer: I have limited experience working on boat motors. I've rebuilt two Sea Doos and a Volvo Penta but I'm not a mechanic!

It sounds like the piston may have seized causing the motor to shut off immediately. Pistons expand with heat and after cooling down, the piston may have become unstuck allowing the motor to start again. First thing I would do is check/change the oil and see the condition and look for even the smallest metals shavings. Drain the oil and run a magnet around the drained oil and see if it picks up anything.
 

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Disclaimer: I have limited experience working on boat motors. I've rebuilt two Sea Doos and a Volvo Penta but I'm not a mechanic!

It sounds like the piston may have seized causing the motor to shut off immediately. Pistons expand with heat and after cooling down, the piston may have become unstuck allowing the motor to start again. First thing I would do is check/change the oil and see the condition and look for even the smallest metals shavings. Drain the oil and run a magnet around the drained oil and see if it picks up anything.
Hopefully not...
Sounds electrical to me. Could be a bad connection somewhere that expands to the point of contact loss with heat and re-contacts when cool. Those can be a hair pulling nightmare to track down.
Best of luck!
 

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Hey folks,
I was wondering if any of you know enough about little Yamaha 2 strokes to answer this question. I have a 2001 9.9 hp, and was running near full throttle last week when the motor just stopped. No sputtering, no rough running ... went from nearly open throttle, little boat up on a plane, to shut off (damned near threw me from the boat). Wouldn't start afterward. Not even a chug.

Ran the electric and paddled the 3.5 miles back to the house. Started on the first pull back at the house and idled just fine. Started and idled just fine when I removed it and prepped it for storage.

Does anybody know if there is a overheat-kill feature on this motor? I was talking with somebody afterward and they made it sound like the motor would shut off if the engine got too hot, but I don't recall having read about that in the manual.

Any thoughts? Any input is welcome. Thanks.

Best regards,
Dogwood
Can't offer much help but the way it quit sounds like ignition. Install spark tester between ignition wire and plug. Run it and see if she quits. Check some yami forums?
 

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Isa pull start bro:rolleyes:
Started on the first pull back at the house
I missed that detail!

He was likely asking if you could pull the rope and feel the piston move, or if the engine was seized......
Yes exactly! Technically a pull start could still not turn over... the string/cable would just be stuck and it would tell you it the piston was seized :D

I had a friend seize his dirtbike in the desert and you could stand on the kickstart without it budging. He let it cool down, added some oil and kicked the piston loose. Rode the rest of the weekend!

He took it home and rebuilt the top end and it kept running until he sold it. I was surprised he didn't do more damage (or maybe he did) riding it after it seized but he didn't grenade the motor so I guess he got lucky.
 

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Discussion Starter #11
it pulled just fine during that period when it wouldn't fire. could definitely hear the pistons working, just wouldn't fire. interestingly, I went and downloaded the owners manual, and under the troubleshooting section, under loss of power, it did mention that a defective thermostat could be an issue. hmmmm. didn't say whether an overheating condition would cause it to die suddenly, but that a defective thermostat could lead to "loss of power" (that term seems kind of ambiguous!)

thanks for the responses, gents. your input is appreciated. I'll look into the coil/cdi thing and see if it matches what was experienced.

ppark, only need two more years out of this boat ... maybe a bit less. then it'll be time for the flats boat with seats that don't compress the disks in your spine on a mildly choppy day
 
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