In your hunt for the perfect trolling motor, you need to know which size to get. Both in terms of shaft length and motor voltage. Ultimately your type of boat will dictate the size of a trolling motor.
A rule of thumb answer is at least 2 pounds of thrust for every 100 pounds of boat weight.
As an industry professional of over 10 years, I’ve needed to size my fair share of outboard motors, so today, I’ll impart my knowledge to you. Here’s a snapshot of what to remember while you read.
At a Glance:
1️⃣ Selecting the appropriate trolling motor size is crucial, considering factors like the prop’s immersion depth and the boat’s weight.
2️⃣ The weight of your boat directly influences the thrust required from your trolling motor. It is recommended to have at least 2 pounds of thrust for every 100 pounds of boat weight.
3️⃣ Electric trolling motors come in 12-volt, 24-volt, and 36-volt options. The right choice depends on your boat’s size, weight, and desired performance.
As I mentioned at the start, the size of an electric trolling motor will also largely depend on the required thrust. This is further explained in my trolling motor thrust guide. Now let’s into it!
🔍 Determining Trolling Motor Size
Choosing correctly is essential to ensure optimal performance and avoid costly mistakes. Here are the guidelines as well as suggestions to help you determine the best trolling motor size for your boat.
Rule of Thumb
The prop of your trolling motor should be submerged 15 to 20 inches below the water. To calculate the ideal shaft length, measure the distance between the deck and the water, then add 15 to 20 inches. This basic calculation will provide a starting point for determining trolling motor size.
Boat Weight and Length
The weight of your boat will directly influence the thrust required from your trolling motor. A common measurement for trolling motor thrust is pounds of thrust.
I recommended having at least 2 pounds of thrust for every 100 pounds of boat weight. To estimate the required thrust, follow these steps:
- Calculate the total weight of your boat, including gear and passengers.
- Divide the total weight by 100 to find the base value.
- Multiply the base value by 2 to determine the required pounds of thrust.
For example, for a boat weighing 2,000 pounds with gear and passengers, you would need a trolling motor with at least 40 pounds of thrust (2,000 / 100 * 2 = 40).
Based on your boat size and weight calculations, you can now assess the appropriate thrust requirements for your trolling motor. Use the following chart as a general guideline for boat length and recommended thrust:
|Estimated Boat Weight (lbs)
|Recommended Thrust (lbs)
|10 – 12 ft
|100 – 300
|2 – 6
|12 – 14 ft
|300 – 500
|6 – 10
|14 – 16 ft
|500 – 700
|10 – 14
|16 – 18 ft
|700 – 900
|14 – 18
|18 – 20 ft
|900 – 1,200
|18 – 24
|20 – 22 ft
|1,200 – 1,500
|24 – 30
🎓 Note: The recommended thrust is calculated as 2% of the total estimated boat weight.
The values in this chart should be treated as a starting point, and it is important to factor in your specific boat weight and conditions when selecting a trolling motor size. For interest’s sake, check out the most powerful models available on the market.
⚡ Voltage and Power
Electric trolling motors come in 12-volt, 24-volt, and 36-volt options. The right choice depends on your boat’s size, weight, and desired performance.
12-volt trolling motors are ideal for smaller boats and offer up to 55 lbs. of thrust. They’re more energy-efficient and require only one 12-volt battery for operation, making them a budget-friendly option. Key points to remember for 12-volt motors are:
- Up to 55 lbs. of thrust
- Requires one 12-volt battery
- Energy-efficient and budget-friendly
For larger boats and higher performance demands, you might need a 24-volt trolling motor. These motors provide between 55 and 80 lbs. of thrust, typically requiring two 12-volt batteries in series to achieve the necessary 24 volts. Key points for 24-volt motors include:
- 55 to 80 lbs. of thrust
- Requires two 12-volt batteries in series
- Greater power for larger boats
If you have a heavy boat or need even more power, a 36-volt trolling motor might be the best choice.
These powerful motors can provide more than 100 lbs. of thrust, capable of moving large vessels like pontoon boats. To achieve 36 volts, you’ll need three 12-volt batteries connected in series. Key points for 36-volt motors include:
- Over 100 lbs. of thrust
- Requires three 12-volt batteries in series
- Ideal for heavy boats and high-performance demands
Understanding your boat’s size, weight, and required performance will help you choose the appropriate voltage and power for your electric trolling motor.
🎯 Factors Affecting Motor Selection
Now that I’ve covered thrust requirements and voltage options let’s turn the conversation to boat types and fishing conditions.
The type of boat you own plays a significant role in determining what size trolling motor you need:
- Bass Boats: For boats designed specifically for bass fishing, a higher thrust trolling motor is often required to maintain efficient speed and power while fishing.
- Pontoon Boats: These boats tend to require higher thrust motors due to their increased weight and larger size compared to other boat types.
- Jon Boats: Smaller and lighter, Jon boats can often be fitted with lower thrust trolling motors, ensuring a longer-lasting battery life.
- Bay Boats: A mid-range trolling motor is usually ideal for bay boats, which strike a balance between size and power requirements.
Fishing conditions such as wind, current, and the speed at which you plan to fish can impact the size and power of the trolling motor you need.
Remembering the rule of thumb that the recommended thrust is calculated as 2% of the total estimated boat weight (fully loaded). You may want to consider a little extra thrust if you encounter strong wind or current while fishing.
Waterline and Shaft Length
Ensure you measure the waterline to deck distance and add the necessary inches to find the ideal shaft length for your trolling motor. For example, if you are using a bow-mount trolling motor and plan to steer it while standing, add an additional 12″ to your measurement.
🔋 Batteries and Runtime
You can’t run your motor without a battery, so spend a good amount of time researching the different options of marine batteries and their effects on your potential run time and running costs.
The size of your battery system will depend on the thrust of your trolling motor. Motors with 55 lbs. of thrust or less require a single 12-volt battery.
For more than 55 lbs. of thrust and up to 80 lbs. of thrust need two 12-volt batteries, creating a 24-volt system.
Larger trolling motors with a higher thrust rating may require a 36-volt battery system, which is achieved by connecting three 12-volt batteries in series.
When it comes to amp-hour ratings, a standard 12-volt trolling motor battery should have at least 100 amp-hours.
You should also consider the type of batteries suitable for trolling motors, such as lead-acid or lithium-ion batteries, each with pros and cons concerning weight, capacity, and endurance.
Run Time Considerations
Accurately calculating the run time will help to ensure you have sufficient battery capacity to cover your fishing trips.
A factor to consider is the depth of discharge (DoD), meaning how much energy is drained from the battery. Shallow discharges significantly increase the battery life, contrary to deep discharges.
To optimize runtime, it’s best practice to use your trolling motor at lower speeds whenever possible, as higher speeds consume more energy, thereby reducing the overall runtime.
Heavier boats will require more thrust, which in turn will consume more battery power. To avoid issues with battery life, ensure you have an appropriately sized trolling motor and battery system for your boat to maximize your time on the water.
🎛️ Control Systems
Larger motors typically come with more bells and whistles. So you need to determine what features you need and factor them into your sizing calculations.
These sizing factors aren’t in terms of power but rather the physical space that they take up.
|Manual control via a handle or tiller.
|Easy to use, affordable.
|Requires close proximity, frequent shift in focus.
|Control via foot pedal system.
|Requires more space, learning curve.
|Wireless system with potential GPS functions.
|Flexible positioning, advanced features.
|May require more battery power and investment.
|App-based control with advanced features.
|Depends on device stability, potential battery drain.
🌟 Popular Brands and Options
Minn Kota Motors
Minn Kota is a reputable brand offering a broad range of electric trolling motors with varying thrust levels, voltage requirements, and shaft lengths. Key models include:
- Endura C2: A classic! The reliable and affordable model is suitable for small freshwater boats, offering 30lbs to 55lbs of thrust and using a 12-volt battery system.
- Terrova: Featuring a 45″ or 60″ shaft, digital-maximizer technology, and auto-stow/deploy system. This advanced trolling motor offers 80 lbs of thrust and a 24-volt battery setup. Great for larger boats and suitable for both freshwater and saltwater use.
- Ulterra: This high-end model boasts a range of sophisticated features, including auto-stow/deploy, power trim, integrated GPS, and Universal Sonar 2. It is available in multiple configurations, with 24- or 36-volt battery systems and thrust levels from 80lbs to 112lbs. Suitable for large boats and professional anglers.
To choose the right Minn Kota model, I recommend consulting their comprehensive buying guide.
🔑 Key Takeaways
Choosing the correct size trolling motor may seem daunting at first, but following the tips in this article should help simplify the selection process.
1️⃣ Several factors should be considered when choosing a trolling motor, such as the type of boat, fishing conditions, waterline and shaft length, and battery types and runtime.
2️⃣ Control systems also play a crucial role in the selection process. Depending on your needs, you may choose between hand control, foot control, remote control, or smartphone app-based control systems.
3️⃣ Consider your specific boating and fishing needs when selecting from diverse trolling motors, like those offered by Minn Kota. Always refer to the manufacturer’s guide for precise selection.
Further insight into how electric trolling motors work will help you better understand what size you might need.