Switching from 12/24 volt to a straight 24 volt

[johnw91]

Hi guys, I was trying to rewire my trolling motor and have ran into some issues. My boat is a 1996 procraft and was designed/ wired for a 12/24 volt trolling motor , in this case a motorguide brute 50 lb thrust. I have another brand new 75 lb thrust 24v motorguide pro edition trolling motor that I am trying to install. I put a 2 wire plug on the 75 lb thrust and whenever i try to plug it in it blows the 40 amp fuses that are connected to the wires that run back to the batteries. At the batteries there are 4 wires , two negative to positive, and there is no connection between the two batteries such as what is on my old boat. The plug receptacle hasthe 4 wires ( two negative and two positive) connected to it. How would i rewire the batteries/ plug receptacle so that it works correctly? Should i run new wires and bypass the fuses? All advice will be greatly appreciated!

 

[dwparker99]

Re: Switching from 12/24 volt to a straight 24 volt

I would convert the four wire system to a two wire system. Disconnect all wires from the batteries and unplug the TM plug. Run a jumper from Bat 1 negative to Bat 2 positive. Find the receptacle wire color that marries with the positive wire from the TM. Connect that wire to the Bat 1 positive. Make sure this wire is protected by a fuse/breaker. Find the receptacle wire color that marries with the negative wire from the TM. Connect that wire to the Bat 2 negative.

The 40 amp breaker you have may not be large enough to carry the max current draw of the new TM. If the breaker trips on high speeds, you will need to go to a 50 amp breaker. Just make sure your boat wire is large enough to support 50 amps.

 

[NYBo]

Re: Switching from 12/24 volt to a straight 24 volt

You could use the current wires by just doubling them up and properly jumpering at the plug. What is the maximum current draw of the new motor? Mr. Parker is probably right: A 50 amp breaker is most likely about right. But check your manual. You only need one breaker, on the positive lead.

 

[johnw91]

Re: Switching from 12/24 volt to a straight 24 volt

thanks for the replies guys, I will look into switching to a 50 amp fuse instead... i looked at the wire i believe it is 10 gauge, do you think that is thick enough for the job?
@NYBo, when you mention jumping at the plug, what would the wire assemblage look like in this case?
thanks once again guys!

 

[NYBo]

Re: Switching from 12/24 volt to a straight 24 volt

Actually, you would have to combine the + and - wires at the receptacle to power two of the connections; you would just wire the plug with the wires from the trolling motor to match the two live connections in the receptacle.

 

[fishrdan]

Re: Switching from 12/24 volt to a straight 24 volt

I will look into switching to a 50 amp fuse instead... i looked at the wire i believe it is 10 gauge, do you think that is thick enough for the job?

I would just do the 50amp breaker(s), 40 amp is too low for a 75#TM. I bet MG or MK would suggest a 60 amp breaker, but those are about $40-50, compared to the less expensive 50 amp breakers that can be used. Use a manual reset breaker only. I have 50 amp breakers on 2- 70# TM's and haven't popped the breakers.

10ga wire, how long are the wire runs?

What type of socket/receptacle do you have? If it's a Marinco 12/24, you need to re-jumper the plug for 24V operation. The Marinco 12/24 plugs can be parallel jumpered for 12V motors or series jumpered for 24V operation. This type of receptacle has 2 pairs of wires running back to the batteries (1 pair for each battery) and it sounds like this might be what you have.

If it's some other type of plug/receptacle, I'd series jumper the batteries and run 24V up to the receptacle.

 

[johnw91]

Re: Switching from 12/24 volt to a straight 24 volt

Thanks once again for the help. I have attached picture of the front of the plug and then the back of the plug receptacle and i have also attached a picture of where the fuses go. Do you suggest i replace these fuses with circuit breakers?
The the boat is 18 feet so its nearly that length.
To sum up the suggestions and see if im thinking about this the way it should be, i should replace the fuses with 50 amp circuit breakers, i should create a series from the batteries with a jumper in between the positive of one and the negative of the other. Of the other four wires, the two negatives should go to one battery's negative and the two positives should go to the other battery's positive terminal. At the plug, i should combine both of the positives onto one of the two positive terminals and do the same for the negatives. Hopefully that came out correctly, let me know if im thinking correctly guys.

 

[fishrdan]

Re: Switching from 12/24 volt to a straight 24 volt

OK, that's not a Marinco 12/24 setup. How many wires are coming out of the plug, 2, 4?

You have a 18' boat, but how long are the wire runs? My boat is 18' too, but the wire run is 22'. 10ga wire (doubled up) is going be marginal as the voltage drop will be too high at wide open on the TM, but OK at lower speeds. Check it out at Blue Seas DC wire calculator. 6ga wire from the stern to helm would be better.

Fuses are OK, breakers are used more often as they can be reset. Myself, I would put a breaker direct onto the battery + terminal and bypass the fuse holders. I wouldn't run 2 fuses parallel on one circuit though. It might work, but I think it's hokey pokey.

I doubt that socket/receptacle is rated to handle the current (about 75 amps at stall speed) of a 75# TM through only 2 pins, I would use all 4 pins to handle the current,,,, if possible. Even at that, I would check to see if the plug/receptacle is getting hot while the TM is being used heavily, hot is bad.

You might be able to get the TM working with the current wiring setup, but I'd upgrade it, new wires, breaker, maybe receptacle/plug. Check out Genuine Dealz for the wiring, crimp terminals and adhesive lined heat shrink tubing.

 

[UncleWillie]

Re: Switching from 12/24 volt to a straight 24 volt

If you are going to attempt to reuse the present hardware;
This is how you will need to rewire it.

One Fuse (not Shown) should be near each Battery POS Terminal.
Doubling up with the present wires will help handle the current.
24 volts will be using LESS amps at the same power levels.

 

[NYBo]

Re: Switching from 12/24 volt to a straight 24 volt

I doubt that socket/receptacle is rated to handle the current (about 75 amps at stall speed) of a 75# TM

It's a 24V model, so the maximum draw should be considerably lower than that.

 

[fishrdan]

Re: Switching from 12/24 volt to a straight 24 volt

It's a 24V model, so the maximum draw should be considerably lower than that.

Whoops, yes you are right, I was stuck in 12V land. I checked a MinnKota 74# TM and it's 45 amps at 24V, at stall speed. Still quite a bit of power.