I have a 98 310 Sundancer. And...

[KCP]

I have a 98 310 Sundancer. And the end of the season on my way to be hauled out for the season I threw an alarm. The alarm was subtle and in the cabin. I could hardly hear it. I came off plane, it stopped. Back up on plane and started shortly after again. The only way I knew it was going off was keeping it on plane and sticking my head in the cabin. Nothing operational happened, that I noticed. It's now time to prep for splash and it's on my mind. Anyone know or have any ideas what it could be? Need to start the hunt. Thanks in advance! 

[wingless]

Welcome to the forum.

The only OEM alarm stuff in the salon and staterooms are the CO detectors.

The symptoms described might not be from valid CO detection, but instead possibly from voltage supply issues or from past end-of-life detectors.

[RMS]

The end of life detectors are likely but agree strange they are not all the time or chirping first. Check bilge pumps. It could be no noise upstairs but alarm down

[gregk]

Not sure if your engine/year has an audible "check engine" alarm/beep, it may sound like it is coming from the cabin. Mine is the same beep as when you first turn the ignition on. It can alarm if an overheat condition occurs which may explain your symptoms. I would check your instruments for temperature and voltage as wingless suggested. Have a friend/family member sit in the cabin to determine the source of the noise.

[SteveR]

More than likely its the CO detector end of life notification but if it is only happening on plane it could be a high water alarm from the front sensor. I had a malfunctioning high water sensor on my 460 Sundancer.

[Kevo]

I used to get an alarm also that was baffling at 1st. It mostly came on while I was cruising with my radar on. It turned out to be the CO detector low voltage alarm.
There's no way to turn it off so I just disconnected it. I have all brand new CO detectors throughout the boat.