Mold isnt all that easy to identify.
Many things look like mold .... like accumulations of 'air pollution
specs', artillery fungus, etc.
X14 (available in grocery stores) and of course chlorox .... only kills
the mold and leaves a residue that gets 'eaten' by something else. .

Strong caustic detergents containing lye (extreme caution) or sodium
silicates such as "tuff-eNuff" .... (made in S. Florida) available
through West Marine will DISSOLVE the cells. If X-14 doesnt 'so the
trick' go to a janitorial supply and get a strong caustic detergent -
(read the safety precautions).

"Artillery fungus" is a common attacker of unprotected/unwaxed gelcoat
and other boat surfaces. It looks like a haze of "little black spots".
You'll need a strong caustic detergent to dissolve it. For recurring
infections of artillery fungus, wipe on one of the clear non-greasy
"athletes foot" remedies .... or any compound containing TIN.