cab,

A bass boost is the last method to use in your particular situation where you've got an acoustic suspension woofer loaded into a free-air application that isn't even isolated front to rear. In fact, a bass boost will add to the problem rather than providing a solution. For now leave your crossover as is. And, take Phil's suggestion on experimenting with the phase.

I see two different paths you could follow to improve your lows given what you have.

If you're absolutely going to stay with your existing mounting configuration, instead of an enclosure, then you've got to convert to a real free-air sub. Sony, Kenwood, Clarion, Alpine, JL Audio and a few others make true free-air subs. JL Audio might make the best free-air sub but 200 watts is a little light for that model. The Alpine would do better with 200 watts. But your MOMO will not sound much better regardless of the steps you take as it is currently being used. Again, Phil is accurate in his assesment of the MOMO's parameters.

As applied to free-air, the distant opening on the port side is a non-issue since the pathlength is so long. However, you would want to seal up the hole atop the hump which is very close to the sub. Total front to rear isolation is critical but only in close proximity (within several feet). Another issue is that the fiberglass hump is constructed with a very thin wall of fiberglass so this mounting surface could be reinforced to create a far more rigid baffle. This would provide a dramatic improvement over what you have now.

Perhaps the best option is to position a side-firing small sealed enclosure over the top of the hump and extending toward the bow. This requires zero modification to the hump other than a carpeted cover panel over the existing opening. You could use your existing MOMO sub for the short term provided it hasn't become too fatigued from running it undamped. Eventually you could replace it with a 2-ohm woofer. This is an easy fit, especially in an '06.

Currently your sub is in the bilge and all of your coaxials are in the coaming, so they do not share space and do not require further isolation. So you're good in that respect.

David
Earmark Marine