I hear engine noise through my tower speakers when the boat is running. As the engine revs and the rpms go higher the high pitch from the tower speakers also gets louder. This noise only comes from the tower speakers, not the in boat speakers. When the boat is off and the stero is on the speakers play fine and so high pitch noise is generated. The tower speakers are run off of a kenwood amp and the boat speakers seem to be ran straight from the head unit. I have a 05 24' sunsport. I have taken all the speakers out of the roswell tower to inspect the wiring and they all have solid connections. The amp is also grounded directly to the battery so I don't see this as being the reason. What else could be causing the noise?