If you have plenty of space then began your selection process with the boat dictating the enclosure. And that will produce your best sub option. For example:
Dual bass-reflex 12W6v3s will offer 79% more surface area and only require 55% more external enclosure displacement as compared to a single 12W7.
Past surface area the biggest factor in bass production is how you direct the bass radiation from a sub/enclosure within a console to the open cockpit. You can maintain 100% of the energy or you can lose 5 to 6 dB (75% lost energy) in the transfer depending on the design. Not to mention, it makes a giant difference in sound quality. Again, that directs you back to the boat at the beginning of your sub design process.