09operator,

Several questions to narrow it down:

  • Verified your batteries are resting at over 12 volts with no alternator?
  • Veified grounds are tight?
  • Tower amplifier powered off Perko common versus battery-direct?
  • Adjusted tower amplifier input gains down?
  • Does noise pitch vary with engine RPM?
  • Does noise level vary with volume changes or remain consistent?
  • Without the tower amplifier on, have you put your ear directly to the other in-boat speakers listening for the noise?
  • Is the noise there only with the engine running or without the engine running and the key powering the engine management electronics?
  • Is the noise in both tower spekaers?


David
Earmark Marine