Budget thrusters

Electric notes
Crossing the bridge, the bigger the wire the better, motor performance is dependent on the voltage supplied. Initially I didn’t have large enough wire which cut the performance by 40% upgrading the wire size across the bridge kicked it up to around 84%. I used 4AWG. The batteries will need to handle this. I chose to use the existing house bank. I have 2 X 6v Trojan T125’s (235AH total) considering the Peukert factor this will give me 30 min to 50% DOD. This is more than enough time for docking/anchoring, for occasional assistance with tacking and use as an electric dagger board.

Parts list & Cost
2 x 60A fuses
1 x 150A fuse
2 x 60” replacement trolling motor shafts
2 x Pontoon mounts
1 x ¼” sheet of starboard
1 x ½ in sheet of starboard
2 x 55lb maxim minn kota trolling motors (digital version is more efficient at lower speeds)
10’ 4AWG marine grade wire (AWG = American wire gauge) to cross the bridge.
12’ 6AWG
3’ 8AWG marine grade wire (shaft inner tube is to small for 6AWG.
Wire terminators, and extensions
1 1/2’ Longer bolts for pontoon mounts
Ordered two new props $80 each

Misc. considerations
1. The motor manual states that the motor is grounded and that the battery bank used for them should therefore be isolated as it may cause corrosion… I ignored this.
2. Cutting up the motor obviously voids any warrantee.
3. The maxim motors are not marine grade. For this reason I made them stowable, but they won’t last forever. The don’t have zincs and the internal wire is not tinned copper. That said you can pick them up on ebay for a reasonable price.

Steve

They look good, same trust as the Minn Kotas, the shaft is a little short however but I guess that would depend on where you mount them. The props are bigger which is good.
One not this is the old set speed controller which is quite a bit more inefficient than the digital infinitely variable versions. If you are only going to use them at full power I don't think this matters to much although I would check that reverse give full power as there are only three reverse speeds as opposed to five forward.

Good luck, let me know how this works out for you.

Steve

That’s a good price for the Salties. I think besides the torqueedo’s folding ability and prop, what you mostly paying for is the LiFePo4 battery. The LiFePo4 batteries are fantastic batteries though and will actually pay for itself in the long, long run, over lead acid, if used regularly.
If I did it again I would do just that. Mount them on drop down outboard brackets. If you mount them low enough those shafts might do. If they are off the transom you could turn them sideways which would probably be a more practical solution. Used just to swing her butt about as I don’t think using them like twin screws would be powerful enough in heavier wind.
Two 12v 100AH batteries should be ample. Although you’ll not get two hours at full power more like 20min to 50% DOD. But then I doubt you’ll ever need more than 10min for docking anyway.

Hey Martin

1. No, it’s a different one I ordered separately. Called a pontoon mount. I believe you can buy motors with the pontoon mount as opposed to the transom mount (which requires a vertical transom to clamp to) but I couldn’t find any with the right specifications.
2. I ordered separate shafts 60” and removed the original shafts. With a bit of effort see post.
3. This sounds good. As long as you have the space for the shaft over the edge of the transom, 3 inches. The dimensions of this mount (in inches) are 6 ½ L X 5 W with the clamp that holds the shaft 3 inches over the side. Those plastic strips are starboard a substitute for plywood.

A windlass foot switch will work or even an automotive winch, bear in mind you’ll need two of them, each one will be hooked up to a bi-directional solenoid (electrically controlled high current switch). This is so that the large wires don’t have to run from batteries to switch at the helm and back down to the motors with would require more distance and consequently larger wire and to handle the higher current. The foot switch in this case has small wires running to the solenoid which does the actual switching.
So you’ll need two bi-directional switches and two solenoids / contactors. These can be mounted after the 60 amp fuse.
These are in fact more efficient than using the original controllers as there is a 4% odd loss in the controllers.
Be very aware of the wire size you’re going to need all the way from the battery/s to get to the transom especially the far side, as voltage drop will directly affect motor performance. There is a calculator on this site that I use http://www.powerstream.com/Wire_Size.htm
It is in imperial units and American wire gauge however. I try shoot for < 3% voltage drop. The shaft will however only accept 8AWG so there’s not much you can do about that last 7’, 5’ of shaft and 2’ to the plug. Voltage drop in high current 12v systems is a pain much, much better with 24v but then most stuff don’t run on 24v. I’m considering moving mine to the stern, but will have to move my hydraulic steering arm somewhere as it’s in the way.