Yanmar 315 engine alarm

[fairtide]

The Yanmar 315 engine alarm sounded for the first time and it took me several seconds just to identify what the sound was. No warning lights were lit and the temperature (per gauge) was normal. I reduced rpm from about 2700 to 1500 while searching for something that was not right. Within perhaps a minute, the alarm shut down, so I continued my trip that whas about half-way completed (a total of two hours one way). There was no further problem during the remaining hour while running on plane at about 13 kts. The complete two-hour return trip after a two-hour layover was without incident.
I don't think that my '06 TE flush deck model has any CO detector that may have been set off, and it seems that the alarm on the instrument panel is dedicated to the engine. Any suggestions?

[zinbaad]

I do hate to admit it but.... On my maiden voyage from Jamesport to NYC (being unfamilier with the electronics) seas were a bit rough banging me around quite a bit twisting & turning. I occasionally heard some sort of beeping alarm sound, no red lights on the gages, oil, battery & temp looked fine. As it turned out I think it was the auto pilot as I attemped to steer while it was engaged, which I realized sometime later.

[Yearwood]

My Yanmar (300 HP) set off an alarm two years ago. Manual was not clear but traced it to engine temperature, per the manual, while the temperature gauge was normal. After a couple of hours messing with the water pump etc. determined it was a water flow sensor. There is a plastic shaft that a float rides on and after riding up and down for years it wore a ridge in the shaft and hung up. Cut the wire to the alarm. Yanmar called on the cell phone and after giving them all the info their educated guess was a faulty alarm, but they had never replaced on. Took the boat in to have it replaced (really a 10 minute job as it sits on top of the engine, but wanted to be sure) a week or two later and then they advised that during the previous two weeks they had replaced two others.