3 way switch, dc motor and polarity chang

I have a 2 DC pumps that I am trying to control with their own On-Off-On switches.   These pumps are for the ballast system in my boat. One pump is for port and the other for the Starboard side. With the first "On", I would like the pump to run clockwise, or pump water in. Off is self explanatory and with the second "On" I would like the pump to run Counter clockwise, or pump the water out.

I previously had this setup working with a DPDT switch, but each pump is rated at 30amps, which I felt is a lot for the switch to handle. I (un)successfully hooked up one relay to the pump and while it worked, the switch, regardless of its on position, only powered the pump in the clockwise direction. I understand that if I swap the leads to the pump, then it will run in the other direction, but how do I use relays to do this for me.

After a lot of research, I am pretty sure the answer is two relays per pump and it would be wired a lot like the examples posted here with the automated door lock.

https://www.the12volt.com/relays/relaydiagram4.html

But what is the difference between the Negative switch trigger and positive with trigger diagram? Since the motor is DC doesn't it mean the pump might just run the opposite way that I think it is going to?

Also, how do I incorporate the on-off-on switch with this because it shows two outputs to the alarm, or in my case pump, neg or positive depending on the negative or positive trigger diagram,

Any information would be super helpful.

Thanks.

Absolutely nothing, it's your choice, the only difference for pos would be a required fuse in the supply. You need 2 x latching SPDT centre off switches for forward and reverse on each pump.
2 things to consider, 30 amps is on the limit for normal SPCO relays of the type you referred to, you might have to go to a specialist supplier such as RAW or Mouser
Try the Mouser catalogue, part no 611D103J1S215NQF it's the exact switch you require.



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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Some DC motors do not change direction with changing polarity.
In those cases you need change only the polarity of the armature (else the stator).

The pump's reversibility is another issue.

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John DeRosa (Hotwaterwizard)
Stockton California
When in doubt, try it out !