Of course it should be mounted in the vicinity of where you are inhaling. Consumers Reports gave the nod to the the First Alert CO615 (rated 87) over the Kidde (rated 66, and which I also have 2 of on the back porch when using the Big Buddy propane heater).
CO detectors rated for marine use measure Time Weighted Average CO
levels...a lot more expensive circuit board detector; and we can dicker over the cost/benefit of that. Also, the board is protected by epoxy coating so less
susceptible to the ravages of moist salt air etc. Of course it's going to
warn me of low voltage; otherwise, if I woke up dead from CO poisoning, I
would immediately hire a lawyer to sue Fireboy for not having such a
warning. The unapproved Home Depot models also must be replaced at
specified interval too, but the Fireboy's internal battery and End of Life
Alarm that Will-C heard makes it more boater-proof. At only 1/10 of a
Boat Unit$, I think the pro-rated Fireboy price of $22.40 a year is pretty
good for what you get. I take it and everything else off the boat in the
off season and they seem to last longer. I also have a RV-marine rated
smoke detector, weigh the 3 fire extinguishers every season and move them
off the boat at 3 years from manufacture (stamped on the bottom of every
extinguisher) or if they lose over 3 oz/year regardless of needle reading. You should do whatever You Think is Best.
Fireboy used to have a re-calibration program where you could return the
unit and for $50 get a replacement every year. I wonder if the CEO saw the movie Blade Runner (the replicants had a 4 year lifespan) and decided
that would be Even More Cool in his product. Great for early Harrison Ford fans.
http://www.amazon.com/Blade-Runner-Fina ... sr_1_1?ie=
UTF8&qid=1409259006&sr=8-1&keywords=blade+runner
We'll bring our ABBA and Air Supply 8-track tapes to the Appalachicola Gathering, so you can play them on your players.
I deeply respect Dr Bob's expert opinion here, and do not want to be interpreted as disagreeing, which I ain't. There is always a lot of room for maneuvering in on THE BEST COMPROMISE FOR YOUR PARTICULAR BOAT, and that is all I'm trying to aim for, for the BEST SOLUTION FOR YOUR PARTICULAR BOAT AND NEEDS.
HAPPY BOATING!
John