When it comes to choosing a trolling motor for your boat, one of the most important factors to consider is the shaft length. The shaft length is the distance between the motor head and the propeller. It’s crucial to choose the right length to ensure the motor operates efficiently and effectively.
The appropriate shaft length for your trolling motor depends on several factors, including the size of your boat, the type of water you’ll be fishing in, and the mounting location of the motor.
The general rule of thumb is to measure from the mounting surface of the transom or bow where the motor will be mounted to the top of the water and add 20″ to get the recommended minimum shaft length.
However if you’ll be fishing in rough water, it’s advisable to add an additional 5″ to the measurement.
Determining the proper trolling motor shaft length is critical to ensure optimal performance and prevent damage to the motor. In this article, we’ll explore the factors that influence the selection of the right shaft length and provide a comprehensive guide to help you choose the perfect trolling motor for your boat.
Understanding Trolling Motor Shaft Length
When it comes to selecting a trolling motor, one of the most important considerations is the shaft length. The shaft length determines how deep the motor will be submerged in the water and how well it will perform.
A trolling motor with the correct shaft length will keep the propeller submerged at the right depth, allowing it to work efficiently and effectively. On the other hand, a motor with the wrong shaft length will cause the propeller to cavitate and reduce the motor’s performance.
Measuring the trolling motor shaft length is a simple process. One can measure from the mounting point on the boat to the waterline. The goal is to have the centerline of the motor and the propeller shaft about 12-18 inches below the waterline.
It’s essential to note that the ideal shaft length for a trolling motor will depend on the boat’s size, weight, and shape. A larger boat will require a longer shaft length to keep the propeller submerged at the right depth.
In general, the rule of thumb is to have the top of the lower unit or foot of the motor covered by at least 12 inches of water. The head of the trolling motor, which is the top part of the shaft with the handle, usually extends around 8 inches above the boat deck. The propeller works best about 12 inches below the water’s surface.
Selecting the right trolling motor shaft length is critical to ensure optimal performance. It’s recommended to measure the distance from the mounting point to the waterline and choose a shaft length that will keep the propeller submerged at the right depth.
Types of Trolling Motors
When it comes to trolling motors, there are three main types: bow mount motors, transom mount motors, and engine mount motors. Each type has its own unique features and benefits that cater to different types of boats and fishing situations.
Bow Mount Motors
Bow mount motors are mounted on the front of the boat and are controlled by a foot pedal or a handheld remote. They are ideal for anglers who want to fish in freshwater, especially in areas with heavy vegetation. Bow mount motors provide excellent maneuverability, allowing anglers to move their boat in any direction with ease. They also offer superior control and accuracy, making them ideal for trolling in windy conditions.
Transom Mount Motors
Transom mount motors are mounted on the back of the boat and are controlled by a hand tiller or a handheld remote. They are ideal for anglers who want to fish in saltwater, especially in areas with strong currents. Transom mount motors are easy to install and remove, making them a popular choice for anglers who want a motor that can be used on multiple boats. They also offer excellent speed and power, making them ideal for trolling in open water.
Engine Mount Motors
Engine mount motors are mounted on the cavitation plate of an outboard motor and are controlled by a hand tiller or a handheld remote. They are ideal for anglers who want to fish in large bodies of water, especially in areas with strong currents. Engine mount motors provide excellent speed and power, allowing anglers to cover a lot of water quickly. They also offer superior control and accuracy, making them ideal for trolling in windy conditions.
The type of trolling motor that an angler chooses depends on the type of boat they have, the type of water they fish in, and their personal preferences. Bow mount motors are ideal for freshwater fishing, transom mount motors are ideal for saltwater fishing, and engine mount motors are ideal for large bodies of water.
Determining the Correct Shaft Length
When choosing a trolling motor, it is important to select the correct shaft length to ensure optimal performance. The shaft length is the distance between the motor head and the propeller. Here are some factors to consider when determining the correct shaft length for your boat.
Waterline Measurement
The waterline measurement is the distance between the waterline and the point where the motor will be mounted on the transom or bow of the boat. To determine the waterline measurement, go to the bow of the boat and measure from the mounting point to the waterline. It is important to take boat measurements when the boat is fully loaded with gear to ensure accuracy.
Bow Rise Consideration
When selecting the shaft length, it is important to consider the amount of bow rise that occurs when the boat is running. If the bow rises significantly, the motor may come out of the water, resulting in reduced performance. It is recommended to add 5 inches to the waterline measurement for fishing in rough water conditions to account for bow rise.
Shaft Length Recommendation Chart
Many manufacturers provide a shaft length recommendation chart to help determine the appropriate shaft length for a particular boat. The chart takes into account factors such as boat size, motor thrust, and transom height. For example, Minn Kota recommends adding 12 inches to the waterline measurement for bow-mount motors and 5 inches for transom-mount motors.
It is important to note that shaft length selection is more critical with bow-mount motors compared to transom-mount motors. Most boat transoms are similar in their distance to the water, and standard transom shaft lengths should be adequate.
Determining the correct shaft length for your trolling motor is crucial for optimal performance. Factors such as waterline measurement, bow rise, and manufacturer recommendations should be considered when making a selection.
Importance of Correct Shaft Length
When it comes to selecting the right trolling motor for your boat, one of the most crucial factors to consider is the shaft length. Choosing the correct shaft length is important to avoid cavitation, prevent damage, and ensure proper submersion of the propeller.
Avoiding Cavitation
Cavitation is the formation of air bubbles around the propeller, which can cause noise and vibration that can scare away fish. Choosing a shaft length that is too short can cause the motor to cavitate, creating fish-spooking noise. The rule of thumb is to have the top of the lower unit or foot of the motor covered by at least 12″ of water. This will help prevent cavitation and ensure that the motor operates quietly and efficiently.
Preventing Damage
Choosing the correct shaft length is also important to prevent damage to the motor and the boat. If the shaft is too long, it can hit the bottom of the lake or river, causing damage to the motor and the boat. On the other hand, if the shaft is too short, the propeller can hit rocks or other underwater obstacles, causing damage to the motor and the boat. It is important to choose a shaft length that is appropriate for the depth of the water and the size of the boat.
Ensuring Submersion
Submersion is the depth at which the propeller is submerged in the water. A trolling motor’s ideal propeller should be at a depth that keeps about 6 inches of water above the blades. In other words, the centerline of the motor and the prop shaft should be about 12-18 inches below the waterline, depending on the make, model, and dimensions of the trolling motor. This will help ensure that the motor operates efficiently and that the propeller is fully submerged in the water.
Choosing the correct shaft length is essential to avoid cavitation, prevent damage, and ensure proper submersion of the propeller. It is important to consider the depth of the water, the size of the boat, and the make and model of the trolling motor when selecting the appropriate shaft length. By following these guidelines, anglers can ensure that their trolling motor operates quietly, efficiently, and effectively.
| Key Takeaways |
|---|
| Choosing the correct shaft length is crucial for the proper operation of a trolling motor. |
| The shaft length should be appropriate for the depth of the water and the size of the boat. |
| A trolling motor’s ideal propeller should be at a depth that keeps about 6 inches of water above the blades. |
Influence of Boat Types on Shaft Length
Kayak and Canoe
Kayaks and canoes are small boats that require a shorter shaft length for their trolling motors. This is because they sit very low in the water and have a shorter distance from the waterline to the motor mount. A shaft length of 24-30 inches is usually sufficient for kayaks and canoes. However, the weight of the kayak or canoe and the intended use should also be taken into consideration when choosing the right shaft length.
Pontoon Boats
Pontoon boats are larger and have a higher distance from the waterline to the motor mount. As a result, they require a longer shaft length. A shaft length of 48-54 inches is usually recommended for pontoon boats. However, the weight of the boat, the size of the pontoons, and the intended use should also be considered when choosing the right shaft length.
Jon and Bass Boats
Jon and bass boats are typically smaller than pontoon boats but larger than kayaks and canoes. They require a shaft length that is in between the two. A shaft length of 36-42 inches is usually recommended for jon and bass boats. However, the weight of the boat, the size of the motor, and the intended use should also be taken into consideration when choosing the right shaft length.
When selecting the right shaft length for a trolling motor, it is important to consider the boat type and its weight. A shorter shaft length is ideal for kayaks and canoes, while pontoon boats require a longer shaft length. Jon and bass boats require a shaft length that is in between the two. It is also important to consider the intended use of the boat and the size of the motor when choosing the right shaft length.
Shaft Length and Water Conditions
When selecting the right trolling motor shaft length, it is important to consider the water conditions you will be using your boat in. The length of the shaft can affect the performance of your motor, especially if the water is rough.
Calm Water
In calm water conditions, a shorter shaft length may be sufficient, as the water does not create much resistance. However, it is still important to ensure that the top of the motor or lower unit is covered by at least 12 inches of water. This will help to prevent the motor from cavitating and losing power.
Rough Water
In rough water conditions, a longer shaft length may be necessary to keep the propeller submerged and maintain optimal performance. This is because waves can cause the boat to rise and fall, which can affect the depth of the motor.
When selecting a shaft length for rough water conditions, it is important to consider the size of the waves you will be encountering. If you fish on saltwater or rough waters, it may be necessary to add an extra 5 inches to your measurement to ensure that the propeller remains submerged.
Table 1 below provides a general guideline for selecting the correct shaft length based on water conditions:
| Water Conditions | Shaft Length |
|---|---|
| Calm Water | Shorter |
| Rough Water | Longer |
It is important to note that these are general guidelines and that the actual length required may vary depending on the size and weight of your boat, as well as the type of motor and propeller you are using.
In summary, selecting the correct shaft length for your trolling motor is critical to ensure optimal performance and prevent damage to your motor. When selecting a shaft length, consider the water conditions you will be using your boat in and ensure that the top of the motor or lower unit is covered by at least 12 inches of water.
Trolling Motor Brands and Shaft Length
When it comes to trolling motors, there are several brands available in the market. Each brand has its own unique features, and it is important to select the right brand and shaft length that suits your boat requirements. In this section, we will discuss one of the most popular trolling motor brands, Minn Kota, and its shaft length options.
Minn Kota
Minn Kota is a well-known brand in the trolling motor industry. They offer a wide range of trolling motors with varying shaft lengths. The shaft length is an important factor to consider when selecting a trolling motor. It is recommended to have the top of the lower unit or foot of the motor covered by at least 12″ of water.
Minn Kota offers standard transom shaft lengths that should be adequate for most boat transoms. However, if you are using a bow-mount motor, shaft length selection is more critical. In such cases, it is recommended to add 9″ for bow-mount hand control motors.
Minn Kota trolling motors come with a warranty that covers defects in materials and workmanship. The warranty period varies for different products, and it is recommended to check the warranty details before making a purchase.
Minn Kota is a reliable brand that offers a range of trolling motors with varying shaft lengths. It is important to select the right shaft length that suits your boat requirements. Additionally, it is recommended to check the warranty details before making a purchase.
Power Considerations
When selecting a trolling motor shaft length, it is important to consider the power of the motor. This section will cover the two main power considerations: thrust and voltage, as well as batteries.
Thrust and Voltage
Thrust is the amount of force that the trolling motor can generate. It is measured in pounds of thrust (lbs). The higher the lbs of thrust, the more power the motor has to move the boat through the water. The appropriate lbs of thrust for your boat will depend on the size and weight of the boat, as well as the type of water you will be fishing in.
Voltage is another important consideration when it comes to power. Most trolling motors operate on either 12 volts or 24 volts. A 12-volt motor will generally be less powerful than a 24-volt motor, but it may be sufficient for smaller boats or calm water conditions.
Batteries
The power of the trolling motor is directly related to the battery that is used to power it. When selecting a battery, it is important to choose one that is compatible with the voltage of the motor. A 12-volt motor will require a 12-volt battery, while a 24-volt motor will require two 12-volt batteries wired in series.
The type of battery is also important. Deep cycle batteries are designed to provide a steady stream of power over a longer period of time, making them ideal for trolling motors. It is important to choose a battery with enough capacity to power the motor for the length of time you will be fishing.
When selecting a trolling motor shaft length, it is important to consider the power of the motor. This includes the lbs of thrust, voltage, and battery capacity. By choosing the right combination of these factors, you can ensure that your trolling motor has the power it needs to move your boat through the water with ease.
Advanced Features and Shaft Length
When it comes to trolling motors, there are a number of advanced features that can affect the appropriate shaft length for your boat. Here are a few things to consider:
Quest: Minn Kota’s Quest feature allows you to set a specific speed and have the motor maintain that speed regardless of wind or current. This feature can be helpful in determining the appropriate shaft length for your boat, as it can compensate for any changes in speed caused by external factors.
Spot-Lock: Another advanced feature on some trolling motors is Spot-Lock, which uses GPS to keep your boat in a specific location. This feature can be useful for fishing, but it also means that you don’t need to worry as much about the length of your trolling motor shaft.
Depth Collar Adjustment: Some trolling motors come with a depth collar adjustment that allows you to easily change the depth of the motor in the water. This can be helpful if you need to navigate shallow water or avoid obstacles.
Extension: If you have a boat with a high transom, you may need to use an extension to ensure that your trolling motor is at the appropriate depth. This is especially important if you plan to fish in shallow water.
Fish-Spooking Noise: Trolling motors can be noisy, which can scare away fish. If you’re concerned about this, look for a motor with a quiet operation or consider using a propeller guard to reduce noise.
Stow: Finally, consider how easy it is to stow your trolling motor. Some motors have a quick-release bracket that makes it easy to remove the motor when you’re not using it, while others require more effort to stow.
These advanced features can affect the appropriate shaft length for your trolling motor, so it’s important to consider them when making your decision.
Freshwater vs Saltwater Shaft Length
When choosing a trolling motor shaft length, it is important to consider the type of water the motor will be used in. Freshwater and saltwater environments have different characteristics that can affect the performance of a trolling motor.
In general, freshwater environments are less harsh on trolling motors than saltwater environments. Freshwater motors do not need to be as heavily protected against corrosion and have fewer seals on the mechanical and electrical components. As a result, freshwater motors can have shorter shaft lengths than saltwater motors.
Saltwater environments, on the other hand, are more corrosive and require trolling motors that are specifically designed for saltwater use. Saltwater motors have more seals and are made with materials that are more resistant to corrosion. As a result, saltwater motors typically require longer shaft lengths than freshwater motors.
When selecting a trolling motor shaft length for saltwater use, it is important to consider the depth of the water, the size of the boat, and the type of fishing being done. A general rule of thumb is to have the top of the lower unit or foot of the motor covered by at least 12 inches of water.
In addition to the general rule of thumb, it is important to consider the following factors:
- Boat size: The size of the boat can affect the amount of water displacement and the amount of drag on the motor. Larger boats will require longer shaft lengths than smaller boats.
- Fishing style: Different types of fishing require different shaft lengths. For example, if fishing in heavy cover, a shorter shaft length may be necessary to avoid getting tangled in the vegetation.
- Water conditions: Rough water conditions may require a longer shaft length to keep the propeller submerged and maintain control of the boat.
It is important to select a trolling motor shaft length that is appropriate for the specific conditions in which it will be used. Freshwater motors can typically have shorter shaft lengths than saltwater motors, but factors such as boat size, fishing style, and water conditions should also be considered.
Frequently Asked Questions
What is the ideal shaft length for a trolling motor on a 20-foot boat?
The ideal shaft length for a trolling motor on a 20-foot boat is between 60 to 72 inches. This is because the shaft length should be long enough to keep the motor’s propeller submerged in the water, even when the boat is riding high on the waves. If the shaft length is too short, the motor’s propeller may come out of the water, causing the motor to cavitate and create noise that could scare off fish.
How to determine the correct shaft length for a trolling motor?
To determine the correct shaft length for a trolling motor, measure the distance from the mounting surface to the waterline of your boat. Add 12 inches to this measurement to account for the height of the motor head above the waterline. This will give you the minimum shaft length you need for your trolling motor.
What is the difference between a 36-inch and a 42-inch trolling motor shaft?
The difference between a 36-inch and a 42-inch trolling motor shaft is the length of the shaft. A 42-inch shaft is six inches longer than a 36-inch shaft. The longer shaft may be necessary if your boat has a high freeboard or if you plan to fish in rough water conditions.
What is the recommended shaft length for a trolling motor on a kayak?
The recommended shaft length for a trolling motor on a kayak is between 24 to 36 inches. This is because kayaks sit lower in the water than other boats, and a shorter shaft length will keep the motor’s propeller submerged in the water.
How to replace a trolling motor shaft?
To replace a trolling motor shaft, first, remove the motor head from the old shaft. Then, remove the old shaft from the mounting bracket. Next, install the new shaft onto the mounting bracket and reattach the motor head. Make sure to tighten all bolts and screws securely.
What is the diameter of a Minn Kota trolling motor shaft?
The diameter of a Minn Kota trolling motor shaft varies depending on the model of the motor. However, most Minn Kota trolling motor shafts have a diameter of 1.25 inches.
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