A good friend of mine wanted to upgrade the sound system in his Avalanche. The original equipment was pretty much worn out by the previous owner and all needed to be replaced, so we gutted it and started fresh.
The stock subwoofer enclosure is built into the floor of the boat and isn't really sealed. I spent a bunch of time spraying expandable foam and undercoating to try to seal it up and deaden the sound and improve the enclosure. The best bet would have been to cut it out and build a proper box, but that wasn't in the scope of this rebuild. I installed a Polk Momo 12" sub and grille.
The stock highs and mids are mounted at floor level which is horrible acoustically. I decided to get them up where you could hear them. That is a challenge in this boat. I installed a set of Polk 6 1/2" separates in the observer dash and installed the midrange of the right side separates in the walkway facing the driver. I installed the tweeter of that set of separates to the right of the driver by the dash. I would have preferred to install the mid on the same plane as the tweeter, but this configuration works well for boats that don't have any good places to place a mid near the driver. You don't get the perfect stereo separation, but you get great sound with plenty of volume for the driver while driving.
The mids in the rest of the cabin were even more work. I built HDPE enclosures on each side that went in the drink holder cubbies. Since I was already building the enclosures, I went ahead and installed dual USB chargers in them. Getting all of the speakers up in the boat massively improved the sound in the cabin and chargers are in great positions. We didn't do anything in the bow to have a "quiet" zone.
For the music source I added a JL Audio Bluetooth receiver and a Clarion EQ. The receiver went in the right side of the dash, next to the throttle control to make it easy to control while driving. I fabricated the EQ plate out of 1/4" HDPE and made room for the 3 surf system controls. Oh by the way we added surf system to the boat at the same time.
Since the stock speaker locations were just holes at the floor now I put in Polk Audio white speaker grills with LEDs where the tweeters went. This allows the storage to breath and made for perfect LED locations around the interior.
For the tower I installed four Polk Audio 6 1/2" speakers in Kicker pods. These worked out great being short and wide on the tower. There is plenty of headroom in the middle of the boat.
Last but not least I built an HDPE amp rack for a Polk 900w five channel amp for the in boats & sub and a Polk 500w two channel amp for the tower speakers. The Promariner onboard charger keeps both batteries charged and ready to go. I extended the plug to the rear walk through. It is easy to just reach over the side and plug it in.
Overall it is a great system on a reasonable budget!! It fit my buddy's needs perfectly.
I forgot to get good pics of the surf system when we finished it, but here are a couple during the install.