My recommendation is to not use a bleach solution on finished surfaces. While it may "kill" some of the mold, it won't prevent a "bloom" which can spread the problem. What you need to do is remove the mold with any good cleaner which should also remove their source of nutrition and slow down a re-infestation. Scott is correct that one of the ways to prevent it is to provide ventilation and lower the humidity. It is recommended that a breathing mask (M-95 or better) be worn while doing the remediation work. There are several materials available to DIYers and most are fairly effective. A good follow up is to be sure to install a good filter element in your boats HVAC returns. A good choice IMO is the 3-M Filtrette. They are available in many stores including HD and Lowes. Try to match the necessary filtration (not necessary to overdo it) with the resistance. 3M offers several levels of efficiency. The greater the filtration, the greater the resistance for air flow, so try to strike a happy medium. Too much filtration can hinder necessary airflow over the coil and cause freeze ups. Clean out your evaporator coils regularly with a liquid coil cleaner and flush with water. The flushed coil cleaner should also help keep your condensate lines clear. BTW, if you're handy, buy the largest size filter element and cut smaller units to size. I believe there is little cost difference between the very large and the smaller sizes and chances are that you won't find an exact size for your boat AC anyway.
Walt
PS I was a NADCA certified mold remediator in a previous life.....