Hi all;
I have been following the thread on CO detectors. I work for a Natural Gas Utility. Part of my job as a service rep is investigating calls where a CO alarm is going off. Co alarms can give false alarms in areas of high humidity. Such as bathrooms or those hot humid days in the summer. If i was going to purchase one for a boat i would try to find one with a digital read out.I'm not sure if they make one of these that is battery powered. Most are 110 volt which would'nt be working when you need it the most.

Also re zinc's i have 2 on my shaft just before the strut.One 5 years old. The other 3 years old. They both appear to be still in good condition. I think it depends on your boat and the water.Fresh or salt as to how long they last. They tend to get eaten away as they get used up as i understand it. You can visually see if they are starting to deteriorate. My 2 cents.