Where exactly?

Nonskid surfaces are notorious for holding and breeding mildew and mold, esp in a damp climate and with neglect. Generally a vigourous scrub, or in extreme cases, a gentle pressure washer will take care of it.

 

Thank you for replying. The mold is on the topside, from bow to stern.

 

Photo attachment

Atempted to attach photo of mold

 

The mold in the picture will/should clean up fine.

However a boat allowed to get to this state is a red flag to look very carefully at the rest of it.

 

Looks like 'artillery fungus', a very common fungus that grows on tree bark in wet climates.
Any 'caustic' type detergent will usually DISSOLVE it: Mild lye solution, TriSodiumPhosphate, SodiumSilicate, .... all the industrial strength 'caustic type' detergents - use with caution. Apply and 'let soak' as it takes time to dissolve. Clorox, etc. can kill it but doesnt dissolve it and the remaining 'dead fragments' then can become the nutrient source for other fungi.

Remaining 'shadows' can usually be easily 'bleached' with oxalic acid (wood bleach) - from a paint or hardware store.

Most probably you will see the same 'growth' on ALL the roofs of buildings in the same area.

 

thank you so much! this is good news because it needs extensive interior work as well.