5 Steps To Select A Trolling Motor

a man fishing in a small boat with a black trolling motor on the transom
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In the market to buy a trolling motor but don’t know which to model pick? I understand your worry, there are many factors that go into choosing a motor. But no need to stress, I have got you covered with my 5 steps to select a trolling motor for your specific needs.

In this article you will learn everything you need to know to choose a trolling motor in 2020. Or if you want to skip to a specific step in this article there is a clickable table of contents. Otherwise, you can read the whole article. Let’s begin.

Step 1. To Select A Trolling Motor: Choose Bow, Transom or Engine Mount

You need to first choose a mounting position for your trolling motor. The two choices are either bow-mounted and transom-mounted. Which one you pick depends on the length, available surface area and type of boat. Each trolling motor type has their own advantages and disadvantages.

Bear in mind though, it’s easier to pull a boat through water than it is to push it. Moving the bow sideways is also easier than it is to move the stern. Thus, bow mount trolling motors give superior boat control over transom mount motors.

Bow Mount

photo of a red boat in water with a black bow-mount trolling motor

A bow mount gets installed at the front/bow of the boat. Anglers prefer bow-mounted trolling motors because it provides precision control of the boat. If you own a vessel over 14 feet in length with room on the bow, this is the ideal type for you. This type steers via hand tiller, hand-held remote and some with a foot control.

The potential downsides are they are harder to install and more expensive than transom mount motors. Plus this type of trolling motor takes up more deck space than comparable transom mount motors.

Keep in mind that installing this a bow mount motor has a few important considerations.

  • One, ensure you use a strong mounting bracket. These tend to come with higher-priced motors.
  • Two, is to install the mount in the right spot on the bow. It’s ideal for the shaft to be center with the bow when the motor is in the submerged position.
  • Three, study the motors’ position in stow and running positions before you drill any holes.

Pro’s: Best Control, Tons Of Features, Hand and Foot Control Options.

Con’s: Expensive, Foot Control Cords Clutter Deck, Take Up More Space.

Looking for a bow mount saltwater trolling motor in 2020?

Transom Mount

closeup photo of a transom-mount trolling motor installed on the stern of a boat

With a transom mount trolling motor you clamp/install it on the stern/back. Select a trolling motor that installs on the transom if your boat is under 14 feet, like an inflatable or kayak. The other main user of transom mounts are sailboats as a primary source of propulsion.

An electric transom motor is a great option for anglers who use the basic trolling technique. For this reason this type is popular on lakes, rivers and ponds that only allow electric motors.

The bonus of a transom mount, is the ease of operation from the back of the boat. Also, it doesn’t clutter up the deck with foot pedals or cords which bow mount motors do. This type is a simple design that’s more affordable than a bow mount design too.

Pros: Less Expensive, Simple Installation, Less Clutter On Vessel.

Cons: Fewer Steering Options, Not As Precise Control.

Engine Mount 

Selective photo of a Minn Kota engine mount trolling motor under light green water

Like the name implies, this type of motor gets mounted onto the cavitation plate of an outboard motor. Or some will mount on an inboard motors’ lower unit. Engine mount trolling motors provide more precision control of an outboard. To steer the user uses the boats steering wheel or by hand. You control the thrust settings and motor direction via a wired remote.

Select a trolling motor like this if you have a multi-purpose boat without room for a traditional trolling motor. No need to worry about added drag with this motor because its only submerged when the engine is off.

For downsides, these motors tend to be harder to control than the others due to the motor pushing the boat. They are also more expensive and have fewer features than bow mount models.

Pros: No Surface Area Requirements.

Cons: Harder To Control, Less Features, Less Affordable Than Others.

Step 2. Identify The Amount Of Thrust Needed

Thrust, is a measurement in pounds of the power of the trolling motor. In layman’s terms it’s the amount of power the motor uses to propel a vessel through the water.

The size and weight of your boat will determine the amount you need. If you own a large and heavy boat you need more thrust to achieve correct control out on the water. Motors with too little thrust result in sluggish, ineffective control of your boat.

Keep in mind, bigger thrust doesn’t equal higher speeds. Think of thrust like “torque” in a car, trolling motor thrust is all about “pull”, not speed. To determine the amount of thrust your boat needs you need to consider the following 3 factors.

1. Boat Weight

The most important consideration to select a trolling motor is the thrust rating. A general rule of thumb is that you need at least 2 pounds of thrust for every 100 pounds of total vessel weight. Total vessel weight refers to the heaviest potential weight. This means you need to calculate it loaded with gear, full fuel and all the passengers. If you aren’t sure of your boats weight, look it up at the NADA vessel directory.

For example:

Your Triton 18 TRX DC bass boat weighs 1690 Lbs empty, plus a total load of 810 Lbs.

The calculation: (1690 + 810) divided by 100 × 2 = 50 Lbs of thrust.

Additionally, chaotic waters tend to lower the speed and power of your boat. You’ll need to use a trolling motor with higher thrust and load the boat with less weight.

2. Location, Conditions and Style of Fishing

Take into account where you do the majority of your boating and what style of fishing you prefer. Spend most of your time on quiet lakes with little wind/currents? You are fine to stick to minimal thrust requirements for the boat. Whereas boating in fast moving water, with big winds or waves, move up at least a level in thrust ratings.

Fishing style comes into play with two factors. One is if you want precise control of the movements of the boat, for this get a bow mount. However, if you only want straightforward trolling a transom mount is fine.

Second, if you want to fish for days without recharging the batteries. For this you will want to consider a motor with a higher thrust rating and in turn a bigger voltage rating. A 70 pound, 24 volt trolling motor will have a much longer run time than a 50 pound, 12 Volt motor.

To estimate the run time of a trolling motor, you do the following equation:

A battery’s amp hour rating divided by the average amperage draw of the motor. Most manufacturers state amperage draw in max amps, to get the average you divide the rating by 2.

For example:

100 amp hour rated battery divided by a 25 average amp draw = 4 hours of run time.

It’s ideal for trolling motors to use specific deep cycle marine batteries.

3. Manufacturer Thrust Charts

Trolling motor brands do their best to help you select a trolling motor with their own charts. It’s important to understand brands test these thrust rating in optimal conditions. They can’t take into account changing weather conditions, loads or location of use.

If your boats weight falls between the least and greatest thrust ratings in a chart, pick the big rating.

It’s in your best interest to decide with your wallet and buy the biggest motor your budget allows.

Step 3. Choose A Correct Shaft Length

After choosing the mount type and a thrust rating you need to pick a shaft length. This is a critical choice for fishermen that pick the bow-mount style. The big mistake with shaft length is picking one that is too short, that allows the propeller to pop out of the water.

A good rule of thumb is to ensure the lower motor sits submerged 10 inches under water.

diagram of stern side of boat showing transom mount trolling motor shaft lengths

To determine the correct shaft length for your motor do the following measurement. Measure between the bow or transom mounting surface and the waterline. Take this measurement and consult the trolling motor brands shaft length table.

diagram of bow side of boat showing bow mount trolling motor shaft lengths

Remember manufacturers test and base their guides and tables on optimal conditions. Boaters who fish in rough water should add six inches to the waterline measurement. Or if you plan to hand-steer a motor while standing add 12 inches to this measurement.

Step 4. Pick 12 Volt, 24 Volts or 36 Volts Power System

Before you pick between a 12, 24 or 36-volt system, it’s vital to understand how each version is set up. Plus the advantages and disadvantages of each.

12 Volt Electric Trolling Motor

A 12-volt trolling motor runs off a single 12-volt, deep-cycle battery. Motors with up to 55 pounds of thrust are 12-volt systems. The main advantages of a 12-Volt system are the low cost, less added weight, and you need a single bank charger. The disadvantage is its lack of prolonged run time, especially if using it at full speed.

High-thrust, 12-volt trolling motors are adequate for boats less than 16 feet in length. But don’t expect full day fishing with this power system.

See The Best Deep Cycle Marine Batteries In 2020

24 Volt Electric Trolling Motor

This type of system runs off two deep cycle marine batteries wired in series. Wiring in series increases the total voltage and wiring in parallel increases battery capacity. 24-volt systems tend to match with motors up to 80 pounds of thrust.

Advantages include: more thrust, more energy efficiency, and it draws fewer amps. Lower amp draw equals longer run times, which is crucial for all day fishing. Disadvantages are the need for a 2/3-bank charger. Plus you need enough surface area to accommodate extra batteries and charger.

Larger motors need more battery capacity. So if you want to fish for over 4 hours and use boats of 16 feet or longer. Use a 24 Volt power system.

36 Volt Electric Trolling Motor

This power system needs three deep cycle marine batteries wired in series. In general large motors that range from 101 to over 112 pounds of thrust use 36-volt battery systems.

The obvious advantage for this amount of battery capacity is for more lengthy run times. The amp draw is tiny compared to 12 or 12 volt systems. As a result, boats using 36-volt power can run all day and is powerful enough to control the biggest boats. Like the previous system the main disadvantage is the onboard weight and size of this system. Plus you need to have at least a 3-bank battery charger.

For serious anglers who use boats over 18 feet in length, a 36-volt system is ideal.

Step 5. How Do You Want To Control The Trolling Motor?

Steering control is a personal preference, but if you aren’t sure where to start, here are some tips. You have three main choices for control, steering via a tiller, remote control or foot control. The tiller is the most basic and is best for slow straightforward steering. Many boaters who own a canoe, kayak or pontoon boat use tiller steered trolling motors.

Boaters who pick an engine mount trolling motor tend to opt for remote control steering. Or some high-end models can steer via a fish finder, like a Minn Kota can with Hummingbird electronics. The obvious reason for using a remote is the motor is underwater on the outboard or inboard motor. A remote is a bonus because its compact and keeps the deck uncluttered.

two angler fishing off boat controlled by bow mount trolling motor on a lake

For fishermen with room on the bow, you have the option for a bow-mount motor. With a bow-mount the options for a remote and/or foot-control exist. Using a remote, the bow or casting platform is clear and you have constant control of the motor.

The disadvantage is that you lose hand control of your rod to make steering adjustments. Whereas with a foot control frees up both hands for fishing. Yet it has cords, wires and the pedal that can be trip hazards on the deck of the boat. Be aware though, foot controls can malfunction at the worse times. Such as when you’re fighting a “Personal-Best” catch.

Which ever type of control you pick be mindful that it’s hard to switch from one to another after you get used to it.

General Considerations To Select A Trolling Motor

Freshwater Versus Saltwater

If you select a trolling motor that is freshwater, only use it in this type of water. Materials used for freshwater motors is basic due to it not needing protection from salt. Below are the three difference that make saltwater models different.

1. Specialized Material & Parts

Saltwater motors run in harsh areas, needing damage-proof shafts and motor heads. These motors use specialized marine-grade materials like corrosion-proof stainless steel, aluminum, or zinc. Which, is then covered in a protective powder-coating with enhanced seals near electronics. Using exhaustive research and design allow the motors to withstand harmful salinity. In turn ensuring a longer life span for your motor.

2. A Sacrificial Anode

The salinity of brackish estuary waters and oceans is very corrosive to metals. To protect crucial metals inside the motor, saltwater models use a sacrificial anode. Anytime two different metals that touch and are underwater, they create a battery. As current flows a special type of corrosion takes place, called galvanic corrosion. Leaving this area unchecked will destroy both metals.

To counteract this corrosion you add a third metal (sacrificial anode) usually zinc. Salt is a great conductor of electric current, which is why these anodes are vital. A sacrificial anode provides optimal durability for your motor for years to come.

3. Price

Since saltwater models, use higher marine-grade materials you need to expect higher prices. Although I always recommend it’s better to pay a high cost once that twice.

If you select a trolling motor that is freshwater, only use it in this type of water.

Don’t Skimp On Power & Charging

The biggest disservice I see from some of my fellow boaters is using cheap, improper power. By this I mean buying the wrong batteries and charging with cheap chargers. Many boaters think that a car battery is fine as a power source, but they are wrong. Car batteries are sometimes called cranking batteries, meant for short bursts of power.

For trolling motors, it’s best to power with high-quality deep-cycle marine batteries. This is due to the design of deep-cycle batteries, which allow for a steady, slow release of power over time. As a result, this type won’t damage your new trolling motor.

When you shop for batteries, buy the best you can afford with the highest ampere-hours (Ah). Using a battery that’s a bit over-sized is always better than an under-sized one.

This important battery rating can help you estimate how long a battery will last on you motor. Do this by matching the Ah rating on the battery(s) to your motors amp draw. Most trolling motors list their amp draw as the amount of current the motor uses as it operates at max speed.

Next, you need to match your high-quality battery(s) with a high-quality charger. Choosing an onboard charger means no more neglect for your trolling motor batteries. I always recommend getting a “smart” charger, because it won’t overcharge the batteries. Most brands provide one, two, three and four bank models for 12, 24 and 36 volt systems.

Eliminate Sonar Interference

This has been a thorn in the side of boater who use fish finders for a long time. It’s the interference between the trolling motor and these types of electronics. Interference is an electromagnetic impulse from a running trolling motor to the sonar. Resulting in the creation of weird visual display issues on the sonar screen. Including the following:

  • Random pixels or target images on the display.
  • The depth sounder function turns off.
  • Erratic depth readings or certain losses of depth readings.
  • Visual noise waves on the display.
  • Screens freezing or blank screen.

Solutions

To solve this nuisance, first try installing the sonar unit to the cranking battery. Thus bypassing and separating the sonar wiring from the trolling motor wiring. It’s ideal to run each set along each side of the vessel.

A second option is to instead turn the sonar sensitivity down. Most sonar units have ranges of 0-100%, turn it down to 75%. If this doesn’t fix it try a snap-on RF Choke. This is s device common to computer to reduce “RF interference.” To use it, you wrap a power cable around the choke 5 times and place it close to the LCD screen. The device acts as an electromagnetic filter.

Another culprit of interference is poor grounding of the trolling motor. Not completing proper ground can allow electrolysis (leaking electrical current) to happen. This is a major source of interference and poor motor performance. Ground the trolling motor to the negative side of the cranking battery. I prefer to run an 18-gauge wire with a two amp in-line fuse to complete proper grounding.

Select A Trolling Motor With Advanced Features

Most anglers love innovative feature to help make their fishing free of frustrations. These days quality trolling motors feature settings such as anchor lock, autopilot and route record capabilities. If you want Bluetooth connectivity, look for motor with a “heading sensor” which allows you to control it with your phone.

What about matching your sonar to a trolling motor? MotorGuide pairs with Lowrance and Simrad electronics. Minn Kota trolling motors have perfect compatibility with Hummingbird imaging sonar units.

With every added bit of technology, expect the cost of the trolling motor to increase.

In Conclusion

By now you are better informed to make the right decision to select a trolling motor. Remember to follow each step and think about the general considerations. For versatile use, buy a saltwater trolling motor. One that has the capabilities to deliver precision control and nuisance free fishing.

As always, thanks for letting Outdoors Informed aid with your research. We love doing it so you can spend less time indoors and more time fishing or boating.

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