I hear from people all the time who've torn out their hair and most of their sanitation system plumbing, trying to get rid of what they think is "head" odor, when all they really needed to do was clean their bilges! 'Cuz a wet bilge is a dark stagnant swamp...and it behaves like one, growing a variety of molds, fungi and bacteria—some that thrive in dark stagnant water, others that just like damp dark places...and it generates the same gasses--hydrogen sulfide and sulfur dioxide--that can make a whole boat smell like a swamp or even a sewer. The warmer the weather and water, the faster they grow. Add some dead and decaying sea water micro-organisms, dirt, food particles, rain water, wash water, hot weather and humidity, plus a little oil or diesel, and you have a real primordial soup…no wonder it stinks!
Most people’s approach to bilge cleaning consists only of throwing some bilge cleaner/and or bleach into that soup when it starts to stink, let it slosh around for a while, then turn on the bilge pump and call it done. I’ve never understood why they think that’s all there is to it. They wouldn’t just add some detergent and bleach to a bathtub full of dirty bath water, swish it around a bit, then just pull the plug and expect the bathtub to be clean. Or just pour some more dishwashing detergent into a sinkful of dirty greasy dishwater, swish it around a bit, then pull the plug and expect to have clean sink. So why do so many boat owners think they can have a clean bilge without any effort and especially without rinsing ALL the dirty water out of it? So if you really want to get rid of odor inside your boat, roll up your sleeves and get to work...you'll be glad you did!
And btw...if you don't have a power washer, get one..they aren't expensive and it'll make the job a lot easier 'cuz it can get water and detergent into areas that are impossible to reach with even the longest handle brushes and mops.
--Peggie