Hydrogen peroxide used at supermarket or drugstore over the counter strength (usually about 3%), not the industrial concentration, will often eliminate
mold and other organisms that create nasty
bilge odors. Spray it on liberally with a garden sprayer, leave it for a day, then rinse with a
water spray with dish detergent added.
Do not bow to the temptation of using a higher concentration of the hydrogen peroxide in hopes of getting better results. It's a strong oxidizer which can provide a spectacular thermal show when it reacts with many substances.