I own a 2011 200 Sundeck with the...

[AncientGeek]

I own a 2011 200 Sundeck with the 5 liter Mercruiser V8.  We keep it on a lake in NH at our lake home and use it perhaps 40 hours a year.  It is in great shape.

This year, on my first ride of the season, I received an alarm for an oxygen sensor problem.  I took it to the local marina for service.  They replaced the starboard O2 sensors as indicated and took it for a water test.  After 30 or 40 minutes, when the service tech was ready to declare success, it went to alarm again for the O2 sensors.  He replaced the port sensors and tried again.  It once again alarmed...all four sensors have been replaced.  He called Brunswick (I believe) and was told to reflash the ECM and did so.  It seemed to work.  I picked up the boat on 7/3 and ran it for about an hour with no problem.  Two days later I started out on a ride and the O2 sensor alarm came on again.

This is nuts.  I'm $800 into this problem and I'm no better off than when I started.  I've read some complaints about O2 sensor issues in various forums, but I haven't seen anything helpful.

Has anyone had this problem and managed to get it resolved?

[wingless]

This page has a useful list of possible causes for this problem.


https://www.engine-light-help.com/oxygen-sensor-codes.html

[AncientGeek]

Thank you. I forwarded that to the marina and asked them to hold on to the original sensors, if they still have them.

[AncientGeek]

I realized I never reported the final resolution to my O2 sensor alarm problem. It turned out that my engine just needed a tune up. The KISS principle once again wins. Start simple and work your way up. The frustrating part of my experience was the misdirection the code offers. It doesn’t point to the problem. It just points to a symptom and apparently even the authorized service center didn’t know what the likely root causes could be. It took several trips and lots of trial and error to get to the simple solution.

[MDM1]

I had the exact same problem in my 2010 SD 260 (350 mag). Ended up just needing a tune-up!

[CharlieM]

I have a friend that owns a car repair place. He says he gets lots of new business from people that have had O2 sensors replaced by various shops and still get codes. The first thing he tells people is “an O2 code is a SYMPTOM, not a diagnosis.” At least a dozen other things can trigger an O2 code.