Xintex Carbon Monoxide Detector
Xintex Carbon Monoxide Det 12v Co Sentinel

Model CMD-4MR 

Use the CMD-4MR carbon monoxide detector for single sites when generator shutdown is NOT desired. 12 VDC operation. Features a state-of-the-art sensor that is unaffected by common cleaning solvents. Lowest current draw of any Fireboy-Xintex CO Detector. UL 2034 Listed for Marine use.

Bought this for the Main Cabin area - $79.13 shipped - Hodges Marine

MTI SA-325 Carbon Monoxide Detector Alarm - Battery Operated.

Bought this for the front V-Berth Cabin from Amazon - $47.82 shipped.

MTI Industries 65-541-WT 12-V Surface Mount Hard Wired Carbon Monoxide Alarm.

Bought this as a backup to store on boat from Amazon - $54.95 plus $7.99 shipping.