I recently hooked up my tower speaker and sub but when i put it in the water the other day i have the whining engine noise through the tower speakers. I know what it is but i need to know how to fix it. I have tried the RCA filter and it works......but....when the filter is on my sub barley moves and you cannot tell its working. Anyone had this happen or know how to fix it??? Thanks in advance.

First: Where is the headunit getting it's power and ground, should be from the same battery as the amp and the best way to do this is go right to the amp's power and ground lugs. Next: are the RCS running parallel to any power or ground cables such as those for the amp(s)?

Not to sure where the headunit is getting power. I just purchased this boat and there isnt any other wire going to the battery other than my amp that i put in there. The RCA's are running parallel with power and ground but only for about 4 feet to the head unit. My amps are underneath the steering wheel.

Rewire the headunit and move the RCA's away from the power cables. Start there and see.

its definitely your rca connector. i suggest you change it.