Trolling Motors - A beginner's guide. (Part 2)

Welcome to Part 2 of a beginner's guide to trolling motors. In part 1 I discussed Mounting Options, Control Options and Thrust. In part 2 of the article I will discuss the choice of Voltage, Batteries and Shaft Length. The choice of these factors is determined by your boat size and purpose of use. Let's start by discussing Voltage rating.

Voltage Rating

Your choice of Voltage will largely depend on what you intend to use your trolling motor for. If you are a casual angler and primarily use your trolling motor for a few hours over a weekend, you'll be well advised to opt for a 12Vdc trolling motor. If you own a tournament type boat (5.3m and longer) and you generally fish whole day tournaments, your choice will be a 24Vdc motor. For guides and fisherman that fish most days of the week and have limited time to recharge batteries, the obvious choice will be a 36Vdc system.

The Voltage rating of your trolling motor is directly proportional to the thrust and endurance of the motor. Keep in mind that your choice of Voltage will impact on the number of batteries you will have to install on your boat, consider that batteries takes up a lot of space and add extra weight to your boat.

Battery Selection

Any 12V lead/acid battery (or 2 in series) can be used to power your trolling motor. It would be wise to understand what amount of current is drawn by your trolling motor before you choose a battery. How do I know what current is drawn by my trolling motor? Most trolling motor manufacturers indicate the amount of current drawn by a trolling motor when operated at maximum speed. Also keep in mind when replacing trolling motor batteries that a 12 volt system requires a minimum of 1.1 to 1.2 amps per pound of thrust, and a 24 volt system requires .85 to .95 amps per pound of thrust.

You can also determine the approximate running time of your trolling motor when operated at maximum speed setting. Parameters needed for this calculation is the motor's amp draw and the battery's amp hour rating. Example: A 12 volt trolling motor drawing 20 amps when used at maximum speed setting, running off a single 120 a/h 12 volt battery will theoretically run for 3.5 hours.

Keep in mind that as the speed setting is reduced the current (amps) drawn by the trolling motor is also reduced. A motor drawing 20 amps at maximum speed may only draw 3 amps at the minimum speed.Thus the same motor mentioned above that will run for 3.4 hours at maximum speed will run for over 20 hours at minimum speed.

Although any lead/acid battery can be used to power your trolling motor, you can expect to get extended service from "deep-cycle" batteries known as dry cells or gel type batteries. The term "deep-cycle" means that these batteries are designed to handle repeated deep discharging (battery voltage as low as 10.5 volts) without negatively affected the battery's intended life expectancy. These batteries are also designed to provide a steady amount of current (amps) over a prolonged period. Good quality "deep-cycle" batteries have thicker cell plates that is capable of storing more electricity and recharge at a faster rate. This type of battery requires very little to no maintenance and is thus ideal for marine applications. It also eliminates the possibility of acid spills in your boat.

Shaft Length

When it comes to shaft length there are various options available to choose from. Take into consideration if you want to use your trolling motor on the transom or bow of your boat.

It is important to measure the distance between the top of your transom/bow to the water's surface. This distance will be used to determine the required trolling motor shaft length suitable for your boat. As a rule of thumb you can add 45cm to the distance between transom/bow and water to determine the shaft length for optimal trolling motor performance.

See table below:

Keep in mind that this is a rough guide to shaft lengths. Please consult the manufacturer's brochure for the specific recommended shaft lengths.

I hope with the knowledge gained in this and the previous article, you'll be in a better position to make an informed decision about the most suitable trolling motor for your boat. In the third and final article I will discuss tips on Boat Control and Positioning. This is a technique that you should master to improve your bass fishing skills.

Ruffneck
Bassing.co.za Pro Staff Member

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