As long as you have the box built right, and mounted solid to the boat, concealed in the engine compartment is fine. Just make sure it stays dry and/or is rated for marine use. mwdill has a 27 Warlock with a single sealed box in the engine compartment and it thumps well. I have a single dual chamber sealed box completely concealed under my back seat, and it hits so hard it lifts the back seat up. I can't keep the girls off the back seat with an empty Corona bottle.