Yamaha F225 four stroke idles rough when warm

[mmiela]

Just start having this issue, engine starts fine and idles fine when cold. After I run it I get about 4800 rpm max and shut it off to drift and fish it starts but idles some what rough and appears to want to stall.

Added sta-bil marine to the tank but haven't been able to run it enough to see of that clears op the issue.

Any thoughts?

 

[wspitler]

I'd check both the engine and boat water separator filters. Pour them into a clear glass container and check for water/contamination. If the vst filter is clogged you'll need to change that. Not a fun job! My guess is bad gas.

 

[mmiela]

I changed the filter in the bilge but not the one the engine. I will check that next.

 

[wspitler]

I'd change both for the few dollars they cost and rule out all but the vst with regard to fuel issues.

 

[Daman858]

The filter on the engine requires a special wrench to get it off. Don't try to use anything else. It's all plastic. Don't ask me how I know this.

 

[wspitler]

I take mine on and off by hand. If you use a large pair of slip joint pliers and don't squeeze too hard., you should be OK. Put a little oil on the O-ring when you put it back on and don't use a wrench to tighten. Just hand tight will not leak if the O-ring is good. The newest version of the filter bowl has large ridges in the sides that make it easy by hand. Older versions are smoother. I had one of the water sensors fail (under warranty) and replaced it. To test the sensor, just take it off and turn it upside down with the ignition switch on and you should get a water in the fuel warning if equipped with that sensor.

 

[seasick]

I don't think that bad fuel will affect performance only when the motor warms up. It should be an issue all the time. Of course changing filters won't do any harm.
What I am concerned about is what the warmed up temp issue might mean. It could be a sensor that is incorrectly measuring a parameter and sending bad info to the ECU. It also could be something more serious such as a head gasket leak as the motor gets hot or a symptom of the exhaust corrosion issue. I would seek out a good mechanic just in case it is something that could lead to motor damage.

 

[mmiela]

So I just dumped the contents of the boat fuel/water separator and found no water at all. So maybe Spark plugs or a LP fuel pump?

 

[mmiela]

I don't think that bad fuel will affect performance only when the motor warms up. It should be an issue all the time. Of course changing filters won't do any harm.
What I am concerned about is what the warmed up temp issue might mean. It could be a sensor that is incorrectly measuring a parameter and sending bad info to the ECU. It also could be something more serious such as a head gasket leak as the motor gets hot or a symptom of the exhaust corrosion issue. I would seek out a good mechanic just in case it is something that could lead to motor damage.

Ugg. I hope it isn't that, I just got this boat and hope to not have to do major repairs or re-power it.

 

[Grog]

It sounds like an injector is sticking.

 

[mmiela]

I don't think that bad fuel will affect performance only when the motor warms up. It should be an issue all the time. Of course changing filters won't do any harm.
What I am concerned about is what the warmed up temp issue might mean. It could be a sensor that is incorrectly measuring a parameter and sending bad info to the ECU. It also could be something more serious such as a head gasket leak as the motor gets hot or a symptom of the exhaust corrosion issue. I would seek out a good mechanic just in case it is something that could lead to motor damage.

Ugg. I hope it isn't that, I just got this boat and hope to not have to do major repairs or re-power it.

Think I can rule out the corrosion issue, just spoke with the previous owner and he had no issue and the motor has 915 hours on it now.

 

[Doc Stressor]

You really need to have the exhaust mid section scoped on that engine. It's time. Just because the previous owner had "no problems" doesn't mean that you aren't showing exhaust corrosion symptoms now. If you have this issue and wait too long, you'll need a new powerhead in addition to the mid section.

4800 rpm at WOT is way too low for that engine. You need to do compression and leak down tests as well.