Yamaha Four-stroke 225 runs rough at idle

topperbt · Jun 9, 2003

Have twin Yamaha f225's new this year. Port engine is a champ runs great, starboard has been problematic from the get-go. Runs rough at idle and has burned a few injectors. Injectors have been replaced twice and still runs rough. Sound coming out of smoke hole like it's misfiring. Also vibrates at idle. Seems like the timing is off. Can you adjust timing? Any ideas?

graddy · Jun 9, 2003

Re: Yamaha Four-stroke 225 runs rough at idle

225 four stroke?

topperbt · Jun 9, 2003

Re: Yamaha Four-stroke 225 runs rough at idle

Yes, sorry, they are Yamaha four-strokes.

Moving Target · Jun 9, 2003

Re: Yamaha Four-stroke 225 runs rough at idle

Is it still under warranty? I would make them fix it till it runs right. Just a thought, could it be a bad ECM?

topperbt · Jun 9, 2003

Re: Yamaha Four-stroke 225 runs rough at idle

They are under a three year warranty but the shop hasn't worked on to many since this engine usually doesn't have problems. Thought someone might have had similar problem and could steer me (them) in the right direction. Has anyone heard of the ECM going bad on these engines? FYI, the engines have 50hrs on them.

DJ · Jun 9, 2003

Re: Yamaha Four-stroke 225 runs rough at idle

topperbt, From what you describe, I'm thinking a lean condition. Check all the fuel connections and make sure you have no air leaks. Especially, on the suction side. Are both engines running from the same fuel tank? If not, try running the poor performing engine with the fuel filler cap loose or a seperate (portable) tank, for testing..

topperbt · Jun 9, 2003

Re: Yamaha Four-stroke 225 runs rough at idle

The engines are both running off the same fuel tank. They also changed all the fuel lines on both engines from the tank to each engine. They also tried running the bad motor off a portable tank, although not for a sustained period of time. You don't think its a timing or computer problem?

DJ · Jun 9, 2003

Re: Yamaha Four-stroke 225 runs rough at idle

topper, Hard to say. I just think it's running lean. If it has an oxygen (O2) sensor, I would be looking there. Or, possibly, throttle position sensor.

seahorse5 · Jun 9, 2003

Re: Yamaha Four-stroke 225 runs rough at idle

The big Yamaha 4-strokes can carbon up the rings and valves internally and cause poor running. That is why they now recommend the use of Ring Free in the 4-strokes mixed 1oz. to 10 gallons. A leakdown test is the only true way to find out if things are carboned up. If they are, connect a 6 gallon tank with 120z. of Ring Free and run the motor. That seems to work as it is the factory recommendation.

CassM · Jun 9, 2003

Re: Yamaha Four-stroke 225 runs rough at idle

I have two 2001 115hp Yam 4-strokes. We have had similar problems (rough idling... and other problems). These started at about 50 hours. First a fuel pump (engine wouldnt start), then we had VST tank problems. They would clog up, or the needle valve was scored, and caused gas to leak back into the engine (check your oil level.. be sure it's not getting higher than normal). Twice we had the VST tanks worked on (on Fuel injected Yam. these are small tanks that store gas before going into the injectors). This last time both engines had the VST tank replaced. They have a fuel pump in them, and a filter (which gets clogged and makes the engine idle rough). I have heard of this problem happening to the newer 225s also. Just a thought...

gypsysoul1 · Jun 6, 2009

Re: Yamaha Four-stroke 225 runs rough at idle

After checking every sensor on my 115 Yamaha 2004 four stroke, I read CassM's post and decided to tackle the job of taking off the VST tank, as my symtoms were getting gas in the oil, rough idle, and gas running out of the air silencer. Sure enough, the needle valve had what looked like a small piece of plastic in it, not allowing the fuel supply to the VST tank to be shut off when full, and allowing fuel to get out the vent line into the air silencer, and thus into the intake manifold. Replaced the needle valve assembly, probably didn't need to. Motor runs fine now, idles great. Thanks for the direction.

Casco Bay Outrage · Jun 6, 2009

Re: Yamaha Four-stroke 225 runs rough at idle

I would be interested to read what Rodbolt says.

Are the mechanics Yamaha certified? If not, take the boat to someone who is.

rodbolt · Jun 9, 2009

Re: Yamaha Four-stroke 225 runs rough at idle

I think the topic starter here needs to find real techs.
use the yamaha dealer locator funtion then go look at certificates on the wall.
master tech would be nice,
remember 5 star certs are a 20 minute video course.

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