Yamaha 4 stroke running rough

[gtcoastie]

Hi, New to the forum but looking for advice. I have twin 2001 Yammy 225 4 stroke saltwater outboards. My stbd engine idles and runs fine then starts sputtering and bucking while losing power. I had a bad trim switch that was previously causing probs and I replaced. First shakedown after was this AM and no joy. Any thoughts?? Thx.

 

[crw1957]

Re: Yamaha 4 stroke running rough

I have a Yamaha 225 four stroke, 2009 model. Similar problem. I drained the water separator filter, the filter on the engine and the VST. All were drained into a glass jar. Found water in the VST. After draining, motor is running fine.

 

[seahorse5]

Re: Yamaha 4 stroke running rough

If the sputtering and bucking occurs while idling a while, there could be a problem with the Idle Air Control (IAC). It gets very hot in normal operation, but a faulty ECU that controls it can also make it act up.

 

[gtcoastie]

Re: Yamaha 4 stroke running rough

Thanks for the input guys. While I thought I had changed all of the fuel filters during normal maintenance, I hadn't. Turned out to be the hidden and not well known (to me at least) 3" cylindrical filter just prior to the VST; not the screen within the VST. Mine probably hadn't been changed in 700 hrs of motoring (I bought at 600 hrs). Initial prognosis seems good at both motors ran without fault for 30 minutes in the drive. This weekend's shakedown will tell for sure.

 

[gtcoastie]

Re: Yamaha 4 stroke running rough

Seahorse5, you hit the nail on the head. My weekend shakedown started out great and I was on top of the world until I powered down and the engine stalled again. After going through the entire fuel system again including cleaning the screen at the bottom of the VST, my mate and I were able to get the engine running. After it cut out a few times, we disconnected the idle air control valve and it ran smooth as silk. Pulled the valve and put power to it; no movement but could feel what is likely a stripped cog internally. Of to the Yammy dealer today for a replacement. Hope to be at full power for the Jupiter Grand Slam DKW tournament this weekend. Thanks!