I don't know if folks scan through the old threads looking for tips and such, but I thought I'd offer something here. We replaced the factory sound system in our 2000 FW H180 with a Kenwood marine system. The deep base is ridiculous. We mounted the Kenwood 10" sub into the kick panel under the captain's console. It probably could have gone on either side. It seems to have worked well because the cavity under the console behind the kick panel is pretty well ventilated into the cavity area behind the panel. That air space opens to the ski locker, the side storage areas, under the front seats, and around into the engine compartment. There seems to be plenty of ventilation back there for the sub to work well. When in the boat, the actual "thump" feels like it's coming from everywhere.
We've been really happy with how well this system turned out in our boat. Deep rich sound, great thump, and clear voice.
In case it helps someone else looking to replace their audio system in their boat, the parts list is posted below: (purchased from Amazon).
Subwoofer and Amp:
https://www.amazon.com/gp/product/B0009 ... UTF8&psc=1Head Unit:
https://www.amazon.com/gp/product/B07BG ... UTF8&psc=16.5" speakers:
https://www.amazon.com/gp/product/B00U7 ... UTF8&psc=1Note: We did not replace the rear speakers in the rear side panels of the boat. We just took those out. Instead, I installed the rear speakers in the rear of the boat, under the back seats on either side of the engine, facing forward. I did this to help push the tunes to the front of the boat better. This also seems to have helped with sound quality in the boat with the speakers not directly facing each other. The front speakers are still in the sides of the boat under the captain's and passenger's consoles where the factory speakers were.
I hope maybe this will help someone else looking for a sweet sound system in their boat!!