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Running issue with 2008 BF225 with 1000 hours.

Thanks. I have cleaned the screen on the IAC valve and the fire screen in the air intake box. The issue must be engine temperature related. I can rev up the engine and let it idle at high RPM (> 1500) for a while. Then the engine won't "stall" after that. I will hook up my diagnostic tool with the engine running next time to see if there is anything out of ordinary.
 
Have you checked valve clearance, they are very critical to achieve a smooth idle. As Janz said too, O2 sensor can be getting old. doesn't always log a fault code. There's nothing to beat getting proper diagnostics, there more to diagnosing an issue than pulling codes. You also need a good understanding of sensor values, you can have a sensor sending an incorrect value without logging a fault. You've done very well so far.
 
Thank you for the reply. I will take a look at the O2 sensor values while the engine is running. A valve adjustment job is planned for this winter. So far I am happy with the engine. It is a 2008 engine with 1050 hours on it. I had it for 9 years and it has been good to me.
 
The war is over in my mind, by skirmishes still happens. I am documenting this for my own records and solicit opinions.

- Engine still stalls when idle at low RPM and cold. Engine will start at around 1000RPM. After 10 - 20 seconds, RPM will drop. If engine is "cold", the engine will "stall". If engine is warm, it will "recover" from the low RPM and start to idle around 800RPM. Suspect it is IAC related.

- Occasionally engine will give alarm when running around 2000-3000RPM and stutters. Shut engine off and start again, engine will be running fine. Pulled code 14-1 which is IAC related. Need to do more research and diagnostic on IAC valve. Is it expensive to replace IAC?

- When engine idle at low RPM <1000, battery light will come on and alarm goes off. Once RPM goes above 1000 RPM, alarm goes away. Suspect weak alternator. Will check and replace/fix alternator at end of season if necessary.

- There is a very small gas leak. Strong gas smell from time to time and show a film of gas on water. Need to check all gas connections and tighten gas filters.

Going to enjoy the season and try to fix issues at the end of season. A boat will never run at 100%. There is always an issue here and there.
 
A fuel leak can allow air into the fuel system, that will cause lots of running issues at idle and all the way through the rpm range. Plus gas fumes are very volatile, you might blow up. Could it be a fuel tank leak- pressure test it. You only need to apply say 2 lbs of air pressure.

An unstable idle can also be a sign of the need to adjust the valves.
 
Some updates. I have to clean up my Idle Air Controller screen often to prevent engine from stalling at low idle (cold engine). The screen is coated with dry and black soot. I can work around and live with this. The small gas leak is still there off and on. I can't see anything with cowling off at idle. The leak is most noticeable when come off a run. It is definitely inside the cowling and not the outside fuel line. Hope it doesn't get worst until end of the season.
 
The fun of owning a boat. Here is my latest troubles. Any ideas or suggestions are welcome.

- I was helping a friend. His anchor snagged some old fishing gear and could not get it up with his winch. I cleated his anchor line onto my boat and tried to drag the whole mess to some shallow water. The "blob" hang up on the bottom and snapped an 1" anchor line. In the process, his boat rammed into my stern. It cracked my transom near my trolling motor mount. Not sure if it is a structure fix or a superficial fix.

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- Went out fishing and got fishing lines wrapped around my propeller. It destroyed the water seal on the lower unit. Not sure how hard it is to replace the water seal around the propeller shaft.
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- At low RPM, my battery alarm goes off. I suspect there is some issues with my alternator. Took it off and will have it rebuild.

- Still have a small fuel leak that comes and goes. Now I have my boat out of water, I will try to track it down.

- Engine is running rich. A lot of dry black soot on IAC valve. Engine still stalls when idle at low RPM when cold. I will look into the heated oxygen sensor. Here is how my exhaust ports look.
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Here is my progress on my boat journey.

- Took the trolling motor and the mounting bracket off. Luckily there is no structure (wood or coosa board) underneath the damage area. Since the mounting hole is through the whole transom, I only see form under the fiberglass. It will be a fiberglass fix only.
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- Found the gas leak. It is a crushed O-Ring on the high pressure fuel filter. It is a very tiny leak that comes and goes.
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- Took alternator to rebuild. My friend was able to replicate the no charging issue on his test bench. He said the marine alternator is different from normal car alternator. He has to do some more research and order some parts. There is a reason why a marine alternator cost > $1200.

- Back to the stalling issue at low RPM. I was investigating the suspected rich burning issue. I was trying to locate a heated oxygen sensor. To my surprise even though I have a 2008 BF225, it is still using the old style heated oxygen sensor (22mm). I thought Honda switched to the new sensor (14mm) in 2007. The marine oxygen sensor is so expensive (> $300). I was debating to get one from Amazon for $50 or not. At the meantime , I did compression test on my engine.
CYLINDERPRESSURE
1215
2205
3210
4210
5195
6210

Cylinder 5 is a bit of concern but overall not too bad. Note to self, remember to put throttle to WOT, when you do compression test. Here are the condition of my sparkplugs.

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My friend said the spark plugs are in good shape. They don't show sign of running rich. He is suspecting my engine is burning motor oil which cause soot to build up on the intake and shows dirty exhaust. He said running rich should not cause build up on the intake/throttle.

Here is sign of the soot on the IAC valve after a few hours of running.
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Here is how my exhaust ports look.
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Given the age of my engine (2008) and hours (1100), I may just have to live with this stalling at idle when engine is cold. I already know how to work around by hold idling at higher RPM. My friend said, I can adjust my idle to higher RPM to get rid of the stall. Any opinion on this? Is there any solution if my engine is burning oil besides pulling the head.
 
I’m not a serious engine rebuilder mechanic, just read stuff that I retain randomly.

If you have good compression, but you are burning oil, would a treatment with Yamaha ring free help?

Your plugs- are they all similarly appearing, or does the one with a bit lower compression look worse, indicating that cylinder is the source of oil consumption?

I had an old car, a 283, it burned oil at 50:1, I called it a 2 stroke. It would foul several plugs completely in about 2 tanks of gas. Switched to synthetic motor oil, it founded them worse.

You’ve found a lot of different issues, keep up the good work. I wonder if that oring gas leak was sucking enough air to cause your miss at idle?
 
All of the spark plugs look similar. No sign of rich burning. Someone pointed me to Yamaha Ring Free earlier this year. I have been using it at high dose for the season. I am going to stop using it for now. It will be while before the fiberglass work is done. I will be going through a "dry" period.
 
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