Gary, Fireboy-Xintex makes several marine CO Detectors. The CMD-1MR-9V is rated for marine use. I have two on my boat and have never had a false alarm. 9V battery. http://www.fireboy-xintex.com/co-detectors.html Here's another one, the Fireboy-Xintex CMD-4MR - this one can be hard-wired to 12VDC. http://www.amazon.com/gp/product/B001JBQEKY/ref=pd_lpo_k2_dp_sr_2?pf_rd_p=48 6539851 <http://www.amazon.com/gp/product/B001JBQEKY/ref=pd_lpo_k2_dp_sr_2?pf_rd_p=4 86539851&pf_rd_s=lpo-top-stripe-1&pf_rd_t=201&pf_rd_i=B000AMA6TS&pf_rd_m=ATV PDKIKX0DER&pf_rd_r=16D6DJ7ZJ3Q6KY5MEPTG> &pf_rd_s=lpo-top-stripe-1&pf_rd_t=201&pf_rd_i=B000AMA6TS&pf_rd_m=ATVPDKIKX0D ER&pf_rd_r=16D6DJ7ZJ3Q6KY5MEPTG Steve Hazlerig SOLARA Seattle, WA