The battle on mold and mildew is a constant one.
Consider a sodium triphosphate solution (TSP) https://www.homedepot.ca/en/home/p.tris ... 30976.html
. Alternatively, if you want a pre-mixed sodium triphosphate solution, you can use a product like https://www.homedepot.ca/en/home/p.mold ... 50815.html
. More money for the same product, but they do claim a "secret" concentration that is better than home-mixing. (B.S., probably).
You don't want to get sodium triphosphate into your local lake or river, though, so it's best applied at home.
Chlorine dioxide is a good way to combat the growth of mold, and to fight the boat-smell:
Slow release system for storage:
https://www.freeportmarine.com/boat-sys ... -slow.html
They also sell a fast release Star Brite chlorine dioxide package, also called a "boat bomb", for a one-time high-concentration treatment.
I painted all accessible sections of the bilge, plus the underside of the hatches with this anti-mold paint: https://www.google.com/shopping/product ... gJTmPD_BwE
Limited success in the bilges, where certain areas of the hull flex like crazy, so I did get some light flaking in certain places. But overall still way better than unpainted, and it worked very well on the underside of the hatches.
Be careful when using multiple cleaning products as they may be incompatible: bleach, when mixed with certain other products (like vinegar!), can create a toxic gas. Bleach, ammonia, TSP, and others all hide in certain cleaning products and you can easily mix up a dangerous concoction.
Those are some of the chemical solutions.
The alternative is active or passive ventilation in an attempt to keep the air fresh, but you can't win the battle on mold with ventilation alone. It helps to keep the bilges as dry as possible, which is a never-ending and unwinnable fight. There are dessicant products available to absorb moisture from the air which also help, but are only a part of the grand scheme. Unfortunately I believe you can't effectively combat mold without a chemical attack.