Minn Kota Electric Motors - Frequently Ask Questions
Minn Kota Electric Motors - Frequently Ask Questions
- What are the benefits of a bow-mounted electric motor?
- What about shaft length selection?
- Can my Minn Kota trolling motor be used in saltwater?
- How important is battery selection for electric motor usage?
- What is Amp Draw?
- What gauge wire should I use for my trolling motor?
- What are the benefits of Minn Kota’s Maximizer?
- How does Maximizer compare to a speed coil?
- Electric motor power ratings are in pounds of thrust. How do I determine the thrust requirements for my boat?
- What is thrust?
- How does thrust compare to horsepower?
- How does thrust compare to speed?
- How do I convert thrust into horsepower?
- What do I do if I experience prop vibration?
Boats do not tend to go in a straight line. Because of this, it is much easier to pull a boat than to push a boat. It is also easier to move the bow of the boat sideways compared to moving the transom. Therefore, a bow-mounted electric motor allows for much greater boat control and positioning. If quick response boat control and positioning is what you are looking for, a bow-mount electric motor is a must.[Back to top]
Choosing the correct shaft length is important so that the angler’s electric motor does not cavitate. The rule of thumb is that the centre of the motor section should be submerged 23cm. In general, shaft length selection is more critical with bow-mount motors versus transom-mount motors. Most boat transoms are similar in their distance to the water, and Minn Kota’s standard transom shaft lengths should be adequate. With bow-mounted motors, there is much greater variation in shaft length requirements. Minn Kota has developed a Shaft Length Selection Guide, shown in the Minn Kota Bow-Mount and Transom-Mount Product sections. This guide requires the angler only to know the approximate distance from the boat’s deck to the waterline.
* Add 125mm to waterline measurement for fishing in rough water. Add 300mm to waterline for steering a hand control while standing.
There is a special line of motors for use in salt or brackish water. The Minn Kota Riptide trolling motors have stainless steel hardware and an advanced painting process for improved corrosion protection. Using any of the standard Minn Kota motors in saltwater may dramatically reduce the life of the motor and voids manufacturer’s warranty. To extend the life of your Riptide saltwater motor, thoroughly rinse the motor with freshwater after every use in saltwater and store indoors. Never leave the motor submerged in saltwater when the boat is moored.[Back to top]
The battery is a critical element of your electric motor system. A high-quality deep cycle marine battery should always be used. Unlike automobile batteries, deep cycle marine batteries are designed to be run down to a discharged state and then recharged. (To extend the life of your battery, always recharge after use. Most trolling motor batteries fail due to lack of proper charging.)[Back to top]
- Amp draw is the measurement of electrical current drawn from a storage battery (or battery), while the motor is being operated.
- Minn Kota’s published amp draw figures represent actual on the water conditions at full power (with all of the motor’s wiring, switches and circuitry in the electrical system as the test measurement is taken).
- Approximate length of running time when operating a motor at full power can be determined with a motor’s amp draw and the battery amp hour rating.
- Example: A single 120 amp hour, 12-volt battery and a 12-volt trolling motor drawing 30 amps at the highest speed setting will run for about 3.4 hours.
- The formula for the calculation is as follows:
.85 A.H.R. = Hours of running time. (A.H.R.= Battery Amp Hour Rating)
M.A.D. (M.A.D. = Motor Amp Draw)
- As the speed setting is reduced the motor amp draw is also reduced.
- A motor drawing 30 amps at high speed may only draw 5 amps at the slowest speed. The same motor that will theoretically run about 3.4 hours at high speed will run for over 20 hours at the slowest speed.
If the incorrect gauge wire is used, there will be a voltage loss to the trolling motor causing a decrease in power and heating of the wires.
Follow the steps and the chart below to determine the proper wire gauge to use:
Step 1. Determine maximum amp draw of your trolling motor and round up to nearest 10.
Step 2. Measure distance from the battery to the power outlet or trolling motor connection.
Step 3. Take the determined length (Step 2) and multiply by two.
Step 4. Select a gauge of wire you think may be applicable. 10 AWG is a good starting point.
Step 5. Consult the Voltage Loss Chart to determine voltage loss per foot so you may match the wire gauge to be used.
Step 6. Take the Determined Length (Step 3) x 2 = Doubled Length. Take the Doubled Length x Voltage Loss = Total Voltage Loss.
Step 7. Work through equation to determine best gauge wire to be used. The best gauge selection will be matched with the lowest voltage loss.
For optimum performance, voltage loss should be between zero and one, but no greater than one.
- Example: You want to run 20 ft of wire in your boat, and the maximum amp draw of the trolling motor is 37Amps.
Step 1. Round up the amp draw from 37 to 40 amps.
Step 2. 20 ft of wire which is needed.
Step 3. Take 20 ft x 2 = 40 ft.
Step 4. Starting with 10AWG. Check the chart above for 40 amps and 10AWG.
Step 5. .0408V is charted for the voltage loss.
Step 6. Take 40 x .0408 = 1.632V — Not acceptable over 1V.
Try 6AWG. In working through the equation it equals .064 — which is under 1 volt, which is acceptable.[Back to top]
The Maximizer offers two primary benefits: infinitely variable speed control and more run time on a battery charge versus a five speed control motor. The infinitely variable speed control feature allows the angler to adjust his motor to just the right power setting for the conditions he’s fishing. The Maximizer is electronic circuitry that uses “Pulse Width Modulation” technology to apply the correct amount of current to the motor unit. Basically, no current is wasted — giving the angler up to five times more fishing time between battery charges.[Back to top]
How Speed Coil Motors Work
- Electrical loads are hooked up in series with the motor such that power from the battery is split between supplying the motor and supplying the additional loads (speed coils).
- Power from the battery is fairly constant regardless of the speed setting. Therefore, on speed 1 for example, more power is diverted to the speed coil than is supplied to the motor. This makes the overall motor assembly less efficient (vs. variable speed/maximizer).
- Extra power consumed by the speed coil produces heat, much like an electrical heating element. The heat is then transferred through the motor housing to the water.
- That is why speed coils are located in the lower motor unit.
Speed Coil Analogy
- You are driving a car at full speed. To slow down, you brake with one foot while continuing to keep your foot down on the acceleration pedal. By doing this, you continue to burn petrol (power) while causing the brakes to heat up.
- Same theory applies with a speed coil motor. The power supply is still constant, but is diverted to the speed coils for the lower speeds which reduces efficiency and run time.
How Maximizer Works
- Since speed coils reduce the power going to the motor, the Maximizer was designed to, eliminate this inefficient speed control method by using rapid on/off switching. The Maximizer is simply a switch that turns the connection to the battery on and off 20,000 times per second.
- If “on” time is longer compared to “off”, the motor runs receive more power. If “off” time is longer, the motor gets less power. Since there is minimal power lost to accomplish this, the overall motor is very efficient.
- You are driving a car fully accelerated. To slow down, you lift your foot off the pedal to decelerate allowing only the proper amount of petrol (power) to be used. This burns less petrol than the first analogy and does not heat up the brake system.
- Same theory applies to the Maximizer. Only the necessary power to go the desired speed is delivered to the motor providing extreme efficiency and longer running time.
- Extended trolling time (up to 5x longer on a single charge).
- The Maximizer speed control saves valuable power over a conventional speed coil motor.
- The Maximizer allows more fishing time on your battery charge, up to five times longer run time per battery charge, compared to the 5-speed switch.
- With infinitely variable speed control, the Maximizer allows for proper speeds to be set and maintained while trolling lures for proper presentation.
- Virtual speed adjustments for changing conditions.
- The Maxmizer allows for fine tune speed adjustments.
- The Maximizer allows the user to control boat speed more effectively in changing environments.
- A feature of the Maximizer, it limits how fast the motor can go from “off” to “on.”
- Soft start helps increase the motor’s life.
More Powerful Motors
- Maximizer electronics allow for more control of higher thrust motors.
- A standard 5-speed switch does not hold up as well under the same conditions.
Momentary/Constant Foot Pedal Switch
- Feature allows the user to switch power on and off while keeping the preferred speed setting.
Thrust requirements are determined by the size and weight of your boat. If you frequently fish in heavy winds, rivers or adverse weather conditions, you may want to consider a higher thrust electric motor. It’s always better to have too much power than not enough![Back to top]
- Thrust is a static measurement in pounds of the motors pushing or pulling power.
- Horsepower is a measurement of “work” being performed.
- One horsepower is a unit of measurement equal to 550 foot pounds of “work” per second.
- There is no direct correlation of thrust to horsepower. Contrary to what you may have been told, fifteen pounds of thrust DOES NOT equal one horsepower.
- As noted in the previous definition, thrust is simply a static measurement of force.
“My buddy has a 36 lb thrust motor, we have the same size boat yet his motor moves his boat just as fast as my 42 lb thrust unit. Why is this?”
- Again, thrust is simply a static measurement of pushing or pulling power, and higher thrust does not necessarily mean greater speed.
- Speed is a factor of prop pitch and motor R.P.M.
- Given motor R.P.M. under load, and Minn Kota’s 4" prop pitch, the approximate speed that a motor will push/pull a small boat can be calculated.
- The formula for this is:
.85 (4x) x 60 = Miles Per Hour
12 5280 (Motor RPM = X)
Many people think that the more pounds of thrust they are getting, the faster the boat will go. This is not exactly true. With trolling motors and outboard motors, boat speed (and acceleration) depends on horsepower and prop pitch. By changing prop pitch, you can trade acceleration for top speed. Minn Kota's trolling motors have props designed for maximum acceleration. When you hit the power, the boat responds immediately. This also allows you to hold the boat in high wind conditions. Top speed with Minn Kota motors and props is about 8 km/h. Small boats will reach this speed with most Minn Kota motors. Larger boats require Minn Kota's largest motors to approach this speed. Comparing Minn Kota motors to gasoline outboards is difficult because most outboard props are designed for much higher speed.[Back to top]
- Props and shafts are not 100% symmetrical.
- Often times simply removing the prop, rotation it 180 degrees, and reinstalling it will lessen or eliminate the incidence of vibration.