Polarity sensing 12VDC relay system

Boat has poorly designed high current 12VDC electric hatch lift actuators where all current for 2 motors (1 per side) runs through operator panel switch and harness. Voltage drop makes motors slow and run at different speeds. Termination end has motors wired parallel to 2 leads that switch polarity depending on op. panel switch position. Is it possible to design a relay system where above 2 leads are control circuit only to actuate relays/contactors that will switch polarity of current (supplied by fused feed direct from batteries) to motors depending on the polarity coming from control circuit? Don't want to run more wiring from operator panel back to hatch if I can avoid it. Thank you in advance.

Sorry-doubt its relevant, but this is a 23 ft. 1995 Mariah Talari Z

I would do it this way: 2 relays required. One will be for UP, and one will be for DOWN. Note: All wiring on 30, 87, and 87a must be capable of carrying the full load of both actuators. My experience is that #10 should be adequate. Fuse or Circuit Breaker for 30 Amps for #10 wire. UP: 87 = Hot at all times. 87a = Ground 30 = To both actuators, lead that is 12V + for UP 85 = Ground 86 = Lead from existing switch that is 12V + for UP DOWN: 87 = Hot at all times. 87a = Ground 30 = To both actuators, lead that is 12V + for DOWN 85 = Ground 86 = Lead from existing switch that is 12V + for DOWN NOTE: Cut the existing wires coming from the panel to the actuators in the place you wish to insert the relays. The lead coming from the panel goes on 86. The lead going to the actuators goes on 30. No real need to keep track of "up" or "down". If you get it backwards, transpose the 86's on the relays. Post back if you need more.

This is basically what you're doing with my above suggestion. You will have the two actuators in parallel:

Hey davep HUGE thanks for taking the time to map this out. I understand completely and will wire a mock-up this weekend and let you know how it works out.

Thanks hotwaterwizard. We were talking here about a negative switched circuit here too. Not sure which Ill use. Did not get to install this yet-kids graduation party, household stuff etc