Minn Kota EM 55 electric trolling motor (3.0hp)

Using an EM with an outboard

The EM 55, EM 80, EM 101, EM 160, EM 202 are all designed primarily to be used with outboard motors. The whole idea is that the motors are bolted onto the cavitation plate of the outboard, the power cable and remote cable are fed up and into the boat and the remote control mounted by the helm. With that set up the electric motor can be steered simply by steering the outboard in the usual manner, and the speed controlled from the helm. Essentially it is exactly the same as using your outboard except without the noise and vibration.

Using an EM without an outboard

The EM can certainly be used as an electric means of propulsion without being mounted on an outboard. Provided that an appropriate mounting position can be found then the motor should function exactly as intended. Please find below some key points to remember:

• The motor should ideally placed so that it passes through clear unobstructed water from below the hull in order to perform at its optimum efficiency.
• The mounting position should take into account the possiblity of grounding, collision or debris all of which could damage the motor.
• If the boat is to be left in the water for long periods of time then we strongly reccomend the motor is removed when not in use. Prolonged submersion may mean the motor is subject to corrosion or fouling (weed growth) for which it was not designed.

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As the motor is not mounted on an outboard which would normally provide articulation and a helm then an alternate method of steering is needed. Normally a suitably placed rudder will suffice for this purpose. If suitable mounting and steering arrangements can be made the Engine mount series of trolling motors from Minn Kota make a very competitive means of propulsion for an electric boat. 

The EM trolling motors from Minn Kota are designed to be mounted on the cavitation plate of an outboard. When the boat is either moving slowly or is a displacement type hull the EM unit is below the water. If mounted to a boat with a planing hull then at speed (being propelled by the outboard) the EM unit is up and out of the water, hence not creating drag and not exposed to any potential collisions with debris.

The remote control unit allows stepless speed control in both forward and reverse throughout the EM trolling motors power range.

Please find above on the left a diagram detailing the critical dimensions for mounting an EM minn kota motor. As mentioned previously the motor is mounted on the cavitation plate of an outboard. Obviously the motor needs to be positioned a certain distance below the waters surface in order to function correctly. Please find the dimensions detailed below:

1. 7.25"
2. 3" (EM 80 & EM 101), 3.75" (EM 55) from the end of the cavitation plate to the spine (shaft) of the outboard, This is to allow mounting of the EM on the plate AND avoid collision of the motor body with the engine shaft.
3. 13" is the distance below the water surface that the EM should be mounted.

Please see above an aerial view of the EM trolling motors mounting bracket. The EM series are primarily designed to be mounted on a 30hp+ outboard, however provided there is enough room on the cavitation plate there is no reason why it should not be mounted on a smaller engine. If you do find the cavitation plate is too small then if you fit a horizontal hydrofoil (doel fin) to the outboard then you should be able to mount the EM unit to that (provided it is strong enough).

There is no reason why you cant mount the Minn Kota on any other appropriate surface that is suitable for bolting onto or bolting through.

How big a motor do I need?

Minn kota provide a rough guide for motor size suited to boat length (please see the table at the bottom of the page); that provides a good starting point for choosing the model to suit your needs. However each boater will use their boat differently and in many different circumstances; a good rule of thumb is to work on the HP rating of each model in comparison to the outboard motor already fitted, that should then give you a good reference for the performance you can expect from your Engine Mounted Minn Kota motor.

The standard specification motors are suitable for freshwater use, the Riptide models are suitable for saltwater use. Both products are priced at the bottom of this page.

An important consideration when choosing the right motor is to be aware of its operating voltage. These are detailed in the table at the bottom of this page. A 12v motor can be supplied from a single battery upwards, a 24v motor needs two batterys connected in series (more pairs can be added to increase the battery bank size), a 36v motor can be suplied from three batteries connected in series (more sets of three can be added to increase the battery bank size). 

How many batteries will I need?

There are some very good websites around that have developed some basic rules for designing an electric boat. The trickiest part of which tends to be getting the battery system right.  We have applied the following rules below to give you a good guide on how many batteries you would need to achieve approximately 4 hours cruising at 50% thrust using your Minn Kota.  Please be aware though, for all those fishermen out there just wanting an hour or so trolling around, you will not need such a large battery bank.

If you want to ask any questions or need any help deciding which may be the best product to choose then please feel free to give us a call on 01353 663095

Reccomendation 1: The average current draw should not be greater than 20% of the battery bank size (e.g 40A for a 200A/hr battery bank)

Reccomendation 2: Maximum current draw should not be greater than 40% of the battery bank size (e.g 80A for a 200A/hr battery bank)

Reccomendation 3: A battery bank should be discharged more than 65% otherwise battery life (cycles) is depleted significantly.

Reccomendation 4: 4 Hours is a good duration guide at 50% thrust, if you require higher thrust for extended periods then size a bigger motor.

We are currently putting together very competitively priced packages for those wishing to do a comprehensive installation of a Minn Kota EM motor. The packages will be made up of:

• EM motor and remote control
• Appropriate size battery bank
• Victron BMV602 battery monitor
• Battery charger to suit the above.

The various packages will be detailed on our website very soon. However, if you are interested in the meantime please feel free to give us a call and we will be very happy to talk through your requirements.