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Discussion Starter · #1 ·
Help needed! Had to end a fishing trip to LA early yesterday due to some issues with my 2008 Yamaha 25 2 stroke.  Background info - Just put on a new PT SRA3 10x12 and it ran perfect on Monday.  Topped off the tank Monday night with fuel at the marina (3 gallons in a 12 gallon tank) and had issues starting first thing yesterday morning.

The motor idles fine, but when you get above 2500-3000 RPMs it will run great for about 45 seconds, then start to bog and lose power.  When it does this, the tiller throttle locks and won't let me give it any gas.  It would then idle rough for about 30 seconds and clear right up.  Run again 45 seconds, bog, etc etc.

It was really frustrating making 45 second runs to get back to the ramp in Delacroix  :mad:

Any ideas?  I figured if it was bad gas from the marina it wouldn't run well at all.  Could it be plugging in the fuel lines causing vapor lock once the RPMs go up?  High temperature shutdown?

I plan on pulling all of the fuel filters and taking a look tonight.

Any input would be great!
 

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Help needed! Had to end a fishing trip to LA early yesterday due to some issues with my 2008 Yamaha 25 2 stroke.  Background info - Just put on a new PT SRA3 10x12 and it ran perfect on Monday.  Topped off the tank Monday night with fuel at the marina (3 gallons in a 12 gallon tank) and had issues starting first thing yesterday morning.

The motor idles fine, but when you get above 2500-3000 RPMs it will run great for about 45 seconds, then start to bog and lose power.  When it does this, the tiller throttle locks and won't let me give it any gas.  It would then idle rough for about 30 seconds and clear right up.  Run again 45 seconds, bog, etc etc.

It was really frustrating making 45 second runs to get back to the ramp in Delacroix  :mad:

Any ideas?  I figured if it was bad gas from the marina it wouldn't run well at all.  Could it be plugging in the fuel lines causing vapor lock once the RPMs go up?  High temperature shutdown?

I plan on pulling all of the fuel filters and taking a look tonight.

Any input would be great!
Now that is something I have never herd before. ???

Is the primer bulb hard when it bogs down?
 

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Discussion Starter · #3 ·
Primer bulb stays hard the whole time.

It's crazy. It'll let me back off on throttle, but won't let me give it any more gas.
 

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Primer bulb stays hard the whole time. 

It's crazy.  It'll let me back off on throttle, but won't let me give it any more gas. 
As in it won't let you turn the handle anymore, or as in when you turn the handle it just doesn't do anything?
 

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This may be dumb question but do you have a tiller extension attached? I have the same motor and I had a comparable experience..

And to add, with the motor off and in neutral my throttle will only advance about 1/4 turn. Is this about the same as yours is doing when in gear?
 

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Discussion Starter · #7 ·
This may be dumb question but do you have a tiller extension attached? I have the same motor and I had a comparable experience..

And to add, with the motor off and in neutral my throttle will only advance about 1/4 turn. Is this about the same as yours is doing when in gear?
Yes and yes. Have a tiller extension, and when it's going through one of these "fits" I can only turn about ~1/4 throttle in neutral.
 

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As weird as it sounds, my issue was with the tiller extension. It was tightened too much and for some odd reason it was not allowing the motor to run full throttle. Took it off, retightened a little less than before and it fixed my issue. Not sure how or why but its a long shot and worth trying..
 

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This may be dumb question but do you have a tiller extension attached? I have the same motor and I had a comparable experience..

And to add, with the motor off and in neutral my throttle will only advance about 1/4 turn. Is this about the same as yours is doing when in gear?
Yes and yes. Have a tiller extension, and when it's going through one of these "fits" I can only turn about ~1/4 throttle in neutral.
Take it to the shop.

The shouldn't be anything stopping the tiller handle from turning once the motor is in gear.

In neutral you can only turn it 1/4 to keep people from over revving the engine.

Sounds like something to do with the lock on the linkage system, although really doesn't explain why it only will run for 45 sec. The linkage is tied to the advance module might be affecting the timing.

Sorry wish I could be more help but I would have to see and run this one to diagnosis it.

Maybe Cut will have a better answer for you, he had one of those engines. I don't work on many 25 Yamaha's to know them like I do the larger ones.
 

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Mine did the same thing as afterhours.

Also this very well could be your problem:
One morning I got to the ramp and went to start the motor, it was a little hard to start but when it did it was idling fine.
Start leaving the dock and the second I start throttling up, it starts bogging down and dies.
Popped the hood, checked it out for a minute and found that the link arm going from my tiller to the timing advance arm was frozen up because I haven't sprayed it down in a while (yea I know shame on me...)
Quickly freed it up and was on my way
 

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Mine did the same thing as afterhours.

Also this very well could be your problem:
One morning I got to the ramp and went to start the motor, it was a little hard to start but when it did it was idling fine.
Start leaving the dock and the second I start throttling up, it starts bogging down and dies.
Popped the hood, checked it out for a minute and found that the link arm going from my tiller to the timing advance arm was frozen up because I haven't sprayed it down in a while (yea I know shame on me...)
Quickly freed it up and was on my way
I was thinking something along the lines of this.
 

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Discussion Starter · #13 ·
Mine did the same thing as afterhours.

Also this very well could be your problem:
One morning I got to the ramp and went to start the motor, it was a little hard to start but when it did it was idling fine.
Start leaving the dock and the second I start throttling up, it starts bogging down and dies.
Popped the hood, checked it out for a minute and found that the link arm going from my tiller to the timing advance arm was frozen up because I haven't sprayed it down in a while (yea I know shame on me...)
Quickly freed it up and was on my way
Cut - Excuse my ignorance, but is the part you're referring to shown on this drawing?

 

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No no
In the first pic #24 is a set of cable ends, on your motor those two ends go to a rotating link cam (hard to explain), from there there is a link going to your carbs, and there's another arm going from the cam to the timing advance under the stator/flywheel.

To simplify things, get some good silicone spray (656, not wd40), and spray the whole motor till its dripping.
Then, advance the throttle (you have to do this while the motor is runnin on ear muffs in gear, so be careful), and make sure when your advancing the throttle that every link arm and joint is moving as it should and feels smooth.
If it does than that's not it. And don't try and adjust anything!
 
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