I am posting this so that others who are having difficulty diagnosing an alarm that would suggest a faulty 02 sensor and have no luck resolving the issue. My engine was actually giving the 02 sensor code to the diagnostic tools used by the dealer. We tried 3 different 02 sensors and still got the alarm/code. The dealer had no idea what was going on and I picked up the boat un-repaired. Be advised there are other problems that can cause this code. (1 second intermittent beep). In my case it turned out that I had 80psi of fuel pressure. I only tested the fuel pressure at the recommendation of others (Skooter) on this forum. I bought the Honda fuel test gauge and got a consistent reading of 80psi at 650rpm. Normal fuel pressure would be 42psi or so. I replaced the fuel pressure regulator and still had 80psi. Then it occurred to me that there are only 2 things that could cause high fuel pressure, a bad fuel pressure regulator or a clogged/pinched return line. As it turns out my return line had been pinched underneath the intake manifold when they reassembled my engine at the dealer. It was impossible to see without removing the intake manifold. I fought this problem for 4 months and replaced a lot of unnecessary parts. However, in the end it was worth it. Keep in mind that high fuel pressure will cause the engine to run rich which leads to the alarm (and a lot of other problems). As soon as I un-pinched the line I got normal fuel pressure and no more alarm. I hope this helps someone else who is chasing down a difficult problem. Be sure you can blow air thru your full pressure return line. (the larger of the two lines that come out of the fuel pressure regulator.)
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