RV Repair: Suburban Gas Water Heater, propane water heater, gas water heater

Question
I have a factory installed Suburban propane water heater Model # SW6 DM on a 5 year old houseboat.  Recently, my carbon monoxide alarm went off.  The water heater was the only source of combustion at the time, so I am thinking it must be the water heater.  It is externally vented.  I could not find any visible seal problems, all windows were shut at the time.   The water heater is working OK, however, it does seem noiser than usual.  The flame is burning a little yellow, but not severely.  There appears to be a small amount of soot in the flu.

It is likely that a sooty flu box and burner assembly are the problem?  

Regards,

J. Krafft  

Answer
I would suspect the detector more than I would the water heater.  RV water heaters are really no brainers.  I am assuming your enclosure is metal but if it's canvas, air can go in and out and so can gases.  Make sure whenever you have any type of gas appliance burning that you have adequate ventilation.  A good stiff wind into the side the heater is on will certainly bring some gas into the interior.  Try another detector and if the problem persists, check for where air is entering the enclosure and try to remedy that.