How big of a boat ? You also have to leave open SLITS at the deck to hull join area to let the sound out.

PT has a 1/2" high point in the center to get it out. Otherwise only water ripples around the hull and a moan.

Found out that General Motors auto speakers are Much more efficient than all those expensive speakers. $ 5 at a auto junk yard. Get the spearer, plug and a few feet of the wire together.

maKes hookup much easier. Medicin kickin in.-------later.

Rich