In my Dynasty open bow with 3.0L mercruiser, I have a sport seating cockpit. 2 bucket seats and a full width bench backs up to the full width sunpad covered bilge/engine compartment.

I did not notice untill the other day that the area between each side of the bench seat, and the side of the boat, has a 4 to 5 inch wide opening from the deck up to the sunpad. I realized that even though this area is hidden, it is a place to allow engine noise to get into the cockpit area.

Id like to seal this area off with wood and maybe even add speakers in the area. Would there be a problem doing this? The bilge already has 2 vents, one on each side of the boat up high, and the blower and proper ductwork. Any ideas?

willie, I doubt there would be any problem with it.
I'll bet the areas are open because your boat came standard with a motorbox cover and two rear seats back there. So those gaps were just the normal under the gunnel area ahead of those seats.

You could always cut out some wood or something to shape, temporarily install it, and then take the boat out on a HOT day and see if it caused any vapor lock or loss of breathing ability for the motor.

I always thought they had those openings so that while you're cruising, fumes are vented. Air comes from the front and pushes it out of the back. Although, mine is always stuffed with PFD.

If I wanted to plug up the noise, I'd use foam.

WaterWing, in the pictures of his boat on the link in his signature, the gaps just look like they happened because of the way the rear bench is contructed. Think about boats with just a motor box cover and a seat on either side. They certainly don't get any air from in front of that engine.