How to Measure Trolling Motor Length?

How to Measure Trolling Motor Length?Determining the proper trolling motor shaft length is crucial in ensuring the motor’s performance and preventing any issues during operation. The shaft length should be long enough to keep the propeller submerged at least 12″ below the water line for optimal functionality. It’s important to consider the specific fishing conditions and prevent the prop from coming out of the water, also known as “cavitation.”

However, finding the right motor length goes beyond just avoiding cavitation. The shaft should not be too long as it can catch on the bottom or become a hassle to stow. Proper shaft length selection is more critical with bow mount motors, as the bow-to-water distances vary more and the bow moves more on the water compared to transom mount motors.

To measure the correct trolling motor shaft length, start by measuring the distance from the mounting surface on the bow to the waterline. Then, add at least 22″ to this measurement to determine the minimum required shaft length. This measurement is essential for preventing the propeller from coming out of the water and ensuring optimal trolling motor performance.

Factors to Consider for Bow Mount Motors

In addition to measuring the proper shaft length, there are several important factors to consider when choosing a bow mount motor for your fishing needs. These factors can greatly impact the performance and functionality of your motor, especially in specific fishing conditions such as rough waters or offshore fishing.

If you frequently fish in rough waters or offshore, it is recommended to select a bow mount motor with a longer shaft length. Adding 25″-27″ to the bow-to-waterline measurement can ensure that the propeller remains submerged even in the presence of additional swell or chop. This will help prevent cavitation and maintain optimal motor performance.

For anglers who prefer standing while steering their motor, it is advised to add 12″ to the recommended transom lengths for easier and more comfortable control. Additionally, you can increase the height of the motor by using a telescoping extension handle, further enhancing steering convenience and maneuverability.

By carefully considering these factors, you can select a bow mount motor that is perfectly suited to your specific fishing needs, ensuring smooth operation and reliable performance on the water.

Measuring Transom Mount Shaft Length

The correct shaft length for transom mount motors is crucial for optimal performance and avoiding any operational issues. While the measurement process may seem simple, it is important to consider all the necessary factors to ensure accuracy.

To begin, it is recommended to measure the distance from the mounting surface on the transom to the waterline. This measurement serves as the baseline for determining the minimum required shaft length. It is crucial to perform this measurement in calm water conditions to get an accurate read.

When measuring, it is also important to account for additional weight on the boat. Factors such as a full tank of fuel and gear can affect the boat’s buoyancy and the bow’s dip in the water. Measuring under “real world conditions” provides a more realistic measurement.

Furthermore, it is essential to consider the weight of the motor and batteries when determining the correct shaft length. These additional components can impact the motor’s position in the water and affect performance. If you find yourself stuck between two sizes, it is recommended to choose the larger size to ensure proper submersion of the propeller.

Importance of Accurate Measurement

Accurate measurement of the trolling motor shaft length is vital to prevent issues such as cavitation and ensure optimal performance. Cavitation occurs when the propeller comes out of the water, leading to reduced thrust and potential damage to the motor.

By measuring the transom mount shaft length correctly, you can avoid these problems and enjoy a smoother and more efficient boating experience. Taking into account factors such as the boat’s weight, additional gear, and motor specifications, you can select the correct shaft length that suits your specific needs and fishing conditions.

Factor Consideration
Distance from mounting surface to waterline Measure in calm water conditions for accuracy
Additional weight on the boat Account for full tank of fuel and gear for realistic measurement
Motor and batteries Consider their weight for proper motor position in the water

By following these guidelines and ensuring accurate measurement, you can select the correct transom mount shaft length for your trolling motor and optimize its performance on the water.

Measuring the Shaft Length of Your Current Motor

When it comes to measuring the shaft length of your current trolling motor, it’s important to follow the correct method to ensure accuracy. The shaft length is typically measured from the base of the motor head to the top of the propeller housing. However, it’s essential to note that different manufacturers may have their own variations in measuring shaft length. While measuring the existing shaft length can provide some guidance, it should not be the sole factor in determining the correct shaft length for your specific needs.

To obtain a more accurate measurement, it is recommended to either use the “rated” shaft length provided by the manufacturer or take a bow to waterline measurement. This measurement involves determining the distance from the mounting surface on the bow to the waterline and adding at least 22″ to determine the minimum required shaft length. Consulting with a local dealer or the manufacturer of your boat brand can also provide valuable insights into typical installations for models similar to yours.

Remember, the accurate measurement of the shaft length is essential for optimal performance and preventing any operational issues. By following the recommended guidelines and consulting the appropriate sources, you can ensure that you select the correct trolling motor shaft length for your boat and enjoy a smooth and efficient experience on the water.

Table: Comparing Measured Shaft Length with Manufacturer’s Rating

Manufacturer’s Rated Shaft Length Measured Shaft Length Difference (if any)
45 inches 44.5 inches -0.5 inches
50 inches 51 inches +1 inch
48 inches 47.5 inches -0.5 inches


In conclusion, the proper shaft length of a trolling motor is of utmost importance for optimal performance on the water. By measuring accurately and considering various factors such as fishing conditions and boat type, you can ensure the propeller remains submerged at the right depth and prevent any operational issues during your fishing trips.

Choosing the correct trolling motor shaft length is critical not only for preventing cavitation but also for maximizing efficiency and reliability. A well-fitted motor shaft will enhance maneuverability and overall performance, allowing you to navigate smoothly in various water conditions.

Remember, measuring the shaft length is just the first step. It’s equally vital to consult the manufacturer’s recommendations and, if possible, seek advice from local dealers or experts who specialize in your boat type. Their expertise can provide valuable insights into typical installations and help you make an informed decision.

To summarize, investing time in determining the proper shaft length for your trolling motor is well worth the effort. The right shaft length ensures optimal trolling motor performance, allowing you to enjoy countless hours of successful and enjoyable fishing on the water.

Richard Dodds

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