I have this is my hunterr5ds bilge, what is it?

Sep 25, 2008
7,495
Alden 50 Sarasota, Florida
Looks like an old battery isolator although it could be an external RF amp for a radio (missing coax) or something else. If you really want to know rather than rely on our guesses, pull it out and look at the label/part number/placard.
 
Jun 11, 2011
1,243
Hunter 41 Lewes
looks like a way to eliminate excess electricity by throwing it into a resistor. Also some scary wiring. perhaps a way to get rid of unwanted solar power?
 
May 24, 2004
7,179
CC 30 South Florida
My best guesses are that it could be a heater to keep water in the bilge from freezing or that it could be some components of a high water level alarm system. Give us a hand and read the placard on the black box and trace the red and black wires to its source.
 
Aug 22, 2017
1,609
Hunter 26.5 West Palm Beach
That green spiral thing is a big fat power resistor. That type is normally used to dump excess energy in systems that have older types of power regulation. The black box has cooling fins, so it would appear to be designed to handle high current. The "brake chopper" type over-voltage protection devices that are used on some types of motor control systems use those. The black box MAY be some sort of overgrown zener diode that is there to protect your house bank from being overcharged by either wind or solar chargers. If the red & black wires go to the house bank, then I am voting that it is an overvoltage protection device.