Trolling Motor Shaft Length: Why It Matters & How to Measure
Choosing the right trolling motor shaft length is crucial for effective fishing. A shaft that's too short won't reach the water properly, while one that's too long can drag on the bottom or get damaged. This comprehensive guide will delve into the importance of shaft length and provide a step-by-step guide on how to accurately measure for the perfect fit.
Why Does Trolling Motor Shaft Length Matter?
The shaft length directly impacts your ability to efficiently and effectively use your trolling motor. Several key factors are influenced by this seemingly small detail:
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Water Depth Coverage: The most obvious factor. A longer shaft allows you to use your motor in deeper water without the prop lifting out of the water. Shorter shafts are limited to shallower depths.
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Obstacle Clearance: A correctly sized shaft ensures your prop avoids underwater obstacles like rocks, logs, and weeds. Too short, and you risk damaging the motor; too long, and you risk dragging the shaft along the bottom.
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Optimal Performance: The prop needs to be fully submerged for optimal thrust and efficiency. An improperly sized shaft negatively affects the motor’s performance, leading to reduced speed and increased battery drain.
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Boat Type and Size: Different boat sizes and types (e.g., jon boat, bass boat, pontoon) require different shaft lengths to accommodate the hull design and typical water depth.
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Mounting Position: The location of your trolling motor's mount on the transom will also affect the necessary shaft length. A higher mount necessitates a longer shaft.
How to Measure for the Right Trolling Motor Shaft Length
Accurately measuring your needs is vital. Here's a step-by-step guide:
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Determine Your Average Fishing Depth: Consider the typical water depth where you fish most often. This is the baseline for your shaft length calculation.
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Measure from the Transom to Waterline: With your boat in the water, measure the vertical distance from the bottom of your trolling motor mount on the transom to the waterline. This measurement should be taken at the boat's normal load and trim.
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Account for Boat Trim: Your boat's trim will affect the final measurement. If your boat is often trimmed up (bow higher), you may need a slightly shorter shaft. Conversely, a trimmed-down boat (bow lower) may require a slightly longer shaft.
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Add Extra Length (Safety Margin): To account for variations in water level and boat trim, add 2-4 inches to your initial measurement. This provides a safety margin ensuring the prop remains submerged even under varying conditions.
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Consider the Prop's Position: Ensure that the prop will be fully submerged at your average fishing depth, even if the boat is lightly loaded or at a different trim level than when you took the measurement.
Frequently Asked Questions
What happens if I use a trolling motor with a shaft that's too short?
Using a shaft that's too short will severely limit your fishing depth. The prop will frequently come out of the water, significantly reducing thrust and efficiency. It can also cause excessive wear on the motor and potentially damage the prop.
What happens if I use a trolling motor with a shaft that's too long?
A shaft that's too long risks grounding on the bottom, especially in shallow water. This can damage the motor, prop, or shaft itself. It will also reduce efficiency and cause unnecessary wear and tear.
How do I know what shaft length I need for my specific boat?
The best way is to follow the measuring guide above, considering your boat’s size, average fishing depth, and typical trim. Consulting with your boat dealer or trolling motor manufacturer's specifications can also be beneficial, especially for more complex hull designs.
Can I adjust the shaft length of a trolling motor?
No, the shaft length is fixed. You cannot adjust it after purchase. Therefore, careful measuring beforehand is crucial.
Where can I find trolling motors with different shaft lengths?
Most reputable sporting goods stores and online retailers that sell trolling motors offer a variety of shaft lengths. Make sure to carefully check the specifications before making a purchase.
By carefully measuring and considering the factors outlined above, you can choose the perfect trolling motor shaft length for your needs, ensuring optimal performance and a more enjoyable fishing experience. Remember, investing a little time in this crucial decision will save you frustration and potential costly repairs down the line.
