How to Measure Shaft Length on Trolling Motor

To measure the shaft length on a trolling motor, measure from the mounting bracket’s base to the shaft’s tip. If you’re thinking of purchasing a trolling motor for your boat, it’s crucial to understand how to measure the shaft length.

Not only will this help you determine the appropriate size for your vessel, but it will also affect the motor’s performance on the water. Measuring the shaft length can be done easily with a few simple steps. In this article, we’ll discuss how to accurately measure the trolling motor shaft length and provide some tips to consider when making your purchase.

How to Measure Shaft Length on Trolling Motor


Understanding Trolling Motor Shaft Length

Definition Of Trolling Motor And Its Components

A trolling motor is an electric motor built to propel a boat at a slow speed, making it an excellent tool for anglers. It’s mounted on either the bow or stern of the vessel and is used to quietly maneuver the boat in shallow waters or around structures.

Trolling motors come with various components, typically consisting of a motorhead, a shaft, a propeller, and foot controls or handheld remote.

Explanation Of Shaft Length And Its Importance

The trolling motor’s shaft length is a crucial factor when selecting a trolling motor. This length, measured from the motorhead to the top of the propeller, determines how deep the propeller sits in the water and how efficient it is in maneuvering the boat.

The longer the shaft, the deeper the propeller sits in the water, and the more control you have over your boat.

How The Shaft Length Affects The Performance Of The Trolling Motor

The trolling motor shaft length significantly influences the efficiency and performance of the trolling motor. Some of the impacts include:

  • Speed: A trolling motor with a longer shaft provides more control over the boat’s direction, creating less resistance, and results in greater speed control.
  • Depth control: A longer shaft results in a lower propeller depth, which means better control over boat drift and water disturbance. It’s essential if you’re fishing in shallow water where sudden movements can scare away fish.
  • Steering control: The shaft length determines the distance between the motor and the stern or bow of the boat, so the longer the shaft, the easier it is to steer and control the boat.
  • Battery life: The shaft length affects how hard the trolling motor has to work to move your boat. The longer the shaft, the more power it needs, and the battery life decreases.

Whether you’re an angler or a boat enthusiast, understanding the importance of trolling motor shaft length is crucial. With this information in mind, you can select the perfect trolling motor shaft length and ensure your vessel’s efficient and effective performance.

Step-By-Step Guide On Measuring Shaft Length

Necessary Tools And Equipment Required

Before you begin measuring the shaft length on your trolling motor, you’ll need to gather a few key tools and equipment. Here’s what you’ll require:

  • A measuring tape or ruler
  • A boat with the motor attached
  • A flat surface for the boat to rest on
  • A helper to hold the boat steady

Measuring The Length Of The Shaft

Now that you have all the necessary tools and equipment, you can begin measuring the length of the shaft on your trolling motor. Here’s how:

  • Place your boat on a flat surface and ensure that it is steady.
  • Locate the top of the trolling motor and measure from the base of the motor head to the top of the motor.
  • Take note of the measurement in inches or centimeters.

Measuring The Distance From The Bracket To The Waterline

Measuring the distance from the bracket to the waterline is crucial in determining the required shaft length. Here’s how to do it:

  • Position your boat in the water at a normal load or weight.
  • Mark the waterline with a piece of tape or a marker.
  • Measure the distance from the bottom of the motor bracket to the marked waterline.
  • Note the measurement in inches or centimeters.

Determining The Required Shaft Length

The final step is to determine the required shaft length of your trolling motor. Here’s how to do it:

  • Add the two previous measurements together (shaft length and distance from bracket to waterline).
  • If the result is between two standard shaft lengths, round up to the next size.
  • If the result is an odd number, round up to the next even size.
  • Ensure that your boat and motor are of similar size and weight to the manufacturer’s recommendations.

By following these simple steps, you can accurately measure the shaft length on your trolling motor for optimal performance on the water.

Common Mistakes To Avoid

Common Errors Made While Taking Measurements

Taking measurements may seem like a straightforward task, but there are common mistakes people make while measuring the shaft length of a trolling motor. Below are some mistakes to avoid:

  • Placing the tape measure on the ground instead of the motor’s base, causing an incorrect measurement.
  • Not using a tape measure at all and trying to eye the measurement, leading to inaccurate measurements.
  • Not taking into account the tiller steering handle when measuring the shaft length, leading to the incorrect measurement.

The Implications Of Incorrect Measurements

It’s essential to take correct measurements because inaccurate measurements can cause several problems. Below are some of the implications of incorrect measurements:

  • An incorrect measurement could lead to the purchase of the wrong shaft length, which would not fit the trolling motor properly, causing a risk of equipment damage or injury.
  • The trolling motor’s performance could be affected, causing issues such as reduced battery life and decreased speed.
  • Incorrect measurements could lead to additional expenses for repairs or replacements due to motor failure.

Tips On How To Avoid Measurement Mistakes

To ensure correct shaft length measurements, follow the tips below and avoid measurement mistakes:

  • Always use a tape measure and place it correctly on the trolling motor’s base to ensure accuracy.
  • Take into account the tiller steering handle, and if possible, remove it before taking measurements for accuracy.
  • Double-check your measurement by taking it twice and comparing the numbers to ensure accuracy.
  • If you’re unsure of how to take measurements or suspect that the measurement could be incorrect, seek expert advice from a trolling motor dealer to avoid costly mistakes.

Taking accurate measurements when determining the shaft length of a trolling motor is crucial to its performance, lifespan, and your safety. By avoiding common measurement mistakes and following the tips outlined above, you can ensure that you purchase and install the right shaft length for your motor.

Choosing The Right Shaft Length

Trolling motors come in different shaft lengths, which can be overwhelming to choose from. It’s important to select the right shaft length for your trolling motor as it affects the overall performance of your boat. Here are the factors to consider when choosing the shaft length.

Factors To Consider When Choosing The Shaft Length

  • Boating conditions: The height of the boat transom above the waterline should be considered when selecting a trolling motor shaft length. If you boat in rough or windy conditions, a longer shaft length is needed to keep the propeller under the waterline.
  • Fishing style: The style of fishing you prefer should also be put into consideration. If you’re a shallow water angler, a shorter shaft length is suitable. For those who enjoy deep water fishing, a longer shaft length is necessary.
  • Motor wattage: The power of the motor affects shaft length selection. A high-powered motor requires a longer shaft length, while a lower-powered motor can work well with a shorter shaft length.
  • Boat size: The size of your boat should be taken into account. A heavier boat necessitates a longer trolling motor shaft.

The Effect Of Boat Size And Weight On Trolling Motor Performance

The weight and size of your boat have a significant impact on the performance of your trolling motor. It’s crucial to select the right trolling motor and shaft length to match your boat’s size and weight.

Here are the effects of weight and size on trolling motor performance:

  • Heavier boats require more thrust to propel forward
  • Larger boats require bigger trolling motors
  • A shorter shaft length may lift the motor out of the water if your boat is too high above the water.

Overview Of Different Shaft Lengths Available In The Market

Shaft length options range from 36” to 72”. The length you choose will depend on your boating conditions, fishing style, motor wattage, and boat size.

Here’s an overview of the different shaft lengths available in the market:

  • Short shaft (15-38 inches): These are perfect for kayaks and small boats with low freeboards.
  • Standard shaft (42-45 inches): These are the most common lengths and work well with boats with low to medium freeboards.
  • Long shaft (48-52 inches): These are ideal for larger boats with high freeboards.
  • Extra-long shaft (54-72 inches): These are required for boats over 23 feet long or boats with exceptionally high freeboards.

Selecting the right trolling motor shaft length will make a significant difference in your boating experience. Consider the factors highlighted above and take the time to choose the option that best suits your situation.

Frequently Asked Questions For How To Measure Shaft Length On Trolling Motor

How Do I Measure The Shaft Length On My Trolling Motor?

To measure the shaft length, measure the distance between the transom mounting surface to the top of the motor. Subtract the distance from the waterline to the transom, and this will give you the shaft length.

Why Is It Important To Measure The Shaft Length?

It is important to measure the shaft length to ensure that the trolling motor is the correct size for your
boat. A motor that is too short may not be effective, and one that is too long may cause drag and reduce boat speed.

How Do I Determine The Correct Length For My Boat?

Measure the distance from the transom to the waterline and add 16 inches to determine the minimum shaft length. If the motor is being used in rough waters, it may be best to choose a longer shaft length.

Can I Use A Motor With A Shorter Shaft Length Than Recommended?

Using a motor with a shorter shaft length than recommended may result in poor performance and reduce boat speed. It may also cause the propeller to cavitate, resulting in damage to the motor and reduced thrust.

How Can I Tell If I Need A Longer Shaft Length?

If the distance between the transom and the waterline is greater than 20 inches, it is recommended to use a
longer shaft length. This will ensure the propeller stays under the waterline and provides maximum thrust.

What Size Shaft Length Do I Need For Saltwater Fishing?

For saltwater fishing, it is recommended to use a longer shaft length of at least 48 inches. This will ensure the
propeller stays fully submerged in choppy water conditions, providing maximum thrust and better control of the boat.


After reading this post, you should now have a good understanding of how to properly measure the length of your trolling motor shaft. It is crucial to measure the shaft length correctly to ensure that your motor is operating at its full potential.

By following the steps outlined in this post, you can easily measure your trolling motor’s shaft length and select the right size motor for your boat. It is important to keep in mind that a properly sized trolling motor will not only improve your boating experience but also help preserve the life of your motor.

Always take accurate measurements and refer to the manufacturer’s guidelines when purchasing a new or used trolling motor. With these tips in mind, you can confidently take your boat out on the water and enjoy a worry-free day of fishing or cruising.

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