Electric thruster setup help please

[TetraFish'n]

There is a local “electric only” lake that I am going to start fishing. It’s a wide open reservoir, around 5000k acres. I have a 20ft aluminum jon(my duck hunting boat) I’ll fish out of. I’m going to borrow the 112 Ulterra from my big boat and mount it on the bow of the jon. I want a second motor for extra thrust. 

 

Trying to custom build this so I can avoid spending three grand on a new trolling motor. I found Minn Kota replacement motors online. I would like to mount one on the stern as a thruster. I’ll use the Ulterra to steer. I can get a 112 motor with shaft to mount on the transom. For you Minn Kota experts, is this doable? What would I need to get to turn the motor on/off and adjust the speed? There is an option for older models and newer Bluetooth models. Would the older legacy models would be the way to go for simplicity?
 

Side note: to keep it lighter weight I’ll be running lithium batteries. 

[casts_by_fly]

You mean to run both at the same time?  You won’t get much more speed if any. 
 

if you want to do it that way with both, I’d sit in the back with the tiller motor and use the remote on the ulterra. Keep one straight and use the other to steer.

[TetraFish'n]

I understand I won’t get more speed, just thrust to carry more weight.
 

My issue is the set up does not have a tiller. It is just a motor with a shaft and the wires running out. There is no head or control board. 

[Jig Man]

Like stated, I don’t think you will benefit much with two motors.  If I were doing it,  I would put an ulterra up front and remotely control it from wherever I am sitting.  
 

I have a 112 Ulterra on a heavy glass boat (probably 3500# +).  Moving across a cove it goes about 3 mph.

[Way2slow]

Your biggest concern should be battery power first and by the time you get enough battery for a reasonable amount of run time, especially if you go with lithiums, you will have a few grand tied up in batteries.  If you go with lead acid, you will a huge amount of weight.

I'm making the assumption your TM is 36 volts going by the size of it.  If I was going to take this journey, my first action would be to start with six,12v batteries and see what king of run time you get, then build from there.

There used to be a web site for electric only boats that had a lot of good info for what you are wanting to do.  Might do a search and see if you can find that.  I've seen people running four TM and half a boat full of batteries back before lithium's.  Some even ran electric fork lift batteries.

[TetraFish'n]

I probably should've prefaced this question with some more information.

 

The intention for two motors isn't for speed, which I already understand will be providing little to no additional speed. My big fishing boat is 22 feet and I have tested the Ulterra and it pushes at 3 mph at 100%.

 

I know the 20ft Jon is a big boat to attempt this with and I would go with a smaller aluminum boat, but I already have this vessel. I need additional thrust to push the weight and mosey along at a reasonable pace and not run the motor at 100% all the time. The amp draw on the batteries will be much lower if I can run both motors at 50 to 75%.

 

It will also be a back up motor in case my bow mount fails. I will try to pick my days wisely, but if it gets windy and wavy, I will also need additional thrust. 

 

I already have the 36V lithium's and I've calculated the runtime. I don't plan on going very far in this rig and will have ample energy.

 

Here is a link to the motor I'm considering mounting on the transom. It will be a stationary mount, only providing forward thrust. I just need to know if it's a reasonable purchase and I can run it with minimal accessories. https://lakesidemarineandservice.com/products/minn-kota-saltwater-ulterra-shaft-tube-and-motor-assembly?variant=40129026326594

 

Thank you, J

[Jig Man]

So you are going to buy a shaft and lower unit, mount it permanently to the boat as a thruster.  Is that correct?

[TetraFish'n]

1 hour ago, Jig Man said:

So you are going to buy a shaft and lower unit, mount it permanently to the boat as a thruster.  Is that correct?

It will have a clamps so that I can remove it when trailering, but yes, otherwise permanent.

[airshot]

When you jerry rig the speed controls that will, in all probability void the warranty !!  

[Jig Man]

Tetra check your pm.

[casts_by_fly]

That’s pretty close to what a lot of kayak guys do, though in the reverse order. Usually you buy a full motor for cheap and then cut the top off.  Build a mount out the back and then hook it up to a controller.  They are just using it for thrust forward instead of paddling or pedaling too much.

 

what you’re talking should work. I don’t know what all comes with that lower unit so you might want to give Lakeside a ring before you buy it. You’ll need a variable power speed controller but there are plenty of those available. You’ll want a fuse somewhere. 

[Jig Man]

Before you buy, lets talk.

[TOXIC]

Did I read it right that the lake is 5,000 acres? I don’t know of any setup that would cover that amount of water.  You might be better off looking at the motors that are like stand alone outboards or the ones that mount to the foot of a big outboard used in trolling. 

[Alex from GA]

I have a friend that built an electric only lake boat.  He mounted 2 trolling motor heads on an outboard lower unit for go and a regular front mounted for fishing.  He's built a couple of these for a local lake.  I don't know any details but have seen the boats.  I can give you his name and number with a PM.

[Bankc]

It depends on the motor, but what a lot of kayak people do in this situation is buy a PWM speed controller and hook that up between the motor and battery.  It'll need to be able to handle the voltage and amperage draw of the motor.  In fact, I'd upsize it to near double the actual amperage you'd pull, just to keep heat down.  I also installed a DPDT waterproof switch rated for the voltage and current that my motor pulls so that I can turn it off, on, and reverse it.  Look up "switch for reversing motor" and you should see how to wire it up.  Though some PWM controllers have reversing options built into them, and most should have an off switch, so you might not need a separate switch, especially if you don't need reverse out of the thruster.    

 

The problem with a PWM controller is it needs to be cool and kept dry.  So you'll probably want to install it into a waterproof box.  And this could overheat the circuit.  What I did to mine was drilled some vent holes and then sealed them up by gluing some KN95 mask filters, because those N95 style masks will pass air, but not liquid.  So it's cheaper than buying purpose build water glands.  It's won't protect it from submersion but will do just fine from splashes and rain.  Of course, a big enough box and sizing the PWM (using one with a much higher amperage rating than you need) so it's not being stressed might allow you to keep the heat down enough that you don't need vent holes.  I'd look for a PWM that doesn't have a fan built in.  The reason being, if it doesn't need a fan, then it doesn't generate as much heat as one that does.  Plus, a fan in a sealed box won't do you much good.