Having the right shaft length on your trolling motor is crucial if you want it to work correctly.
This is especially true for the motors mounted on the boat’s bow, as the distance from the bow to the waterline can vary greatly from boat to boat.
In this article, you’ll learn about the necessary steps you need to take to get the correct shaft for your motor.
Why the Shaft Length Is So Important
Thrust or power delivered by your trolling motor is essential, but it is only one factor that will affect your boat’s performance. All this power will amount next to nothing if your trolling motor is not submerged deep enough.
Selecting the right shaft of your trolling motor is vital. The shaft must be long enough for the propeller to stay submerged at least 16″ below the water line regardless of water and weather conditions.
You don’t want the propeller to get out of water in choppy waters or/and suck in air from above the waterline when it is not deep enough. It will cause noise, and loss of power and can shorten the life of your motor.
Measure the Distance to the Waterline
As a rough guide, you will need to measure the distance from your chosen mounting location to the water level.
Bow Mount Motors
There are a few different ways to do this, but the easiest is to use a tape measure:
Step 1. Go to the bow of your boat.
Step 2. Unwind the tape measure from the location of where your trolling motor will be mounted to the waterline.
Step 3. Take the reading and write it down.
You should take your measurements when your boat is fully loaded with gear. If possible, take into account the weight and the location of the batteries. On a light boat, the weigh distribution can make a huge difference to the motor’s performance.
Also, make sure that you measure the distance to the waterline when the water is calm. Otherwise your readings won’t be accurate.
Transom Mount Motors
If you want a trolling motor that mounts on your transom, things are usually less complicated. This is because most boats have transoms at a similar height.
Minn Kota recommends the following shaft length for different transom heights:
- 30″ shaft for transoms up to 10″ high
- 36″ shaft for transoms up to 16″ high
- 42″ shaft for transoms up to 20″ high
Engine Mount Motors
Engine mount trolling motors are fixed to the cavitation plate of outboard motors. Before you buy the trolling motor, you should check if the plate is deep enough under the waterline. There should be a minimum of 13 inches of submersion for the trolling motor to function correctly. If not, you will need to buy an extension.
Shaft Length for Different Boat Types
The size and type of your boat will also play a role in deciding the right shaft length. In general, the longer and heavier your boat, the longer the shaft should be.
For most popular pontoons, a shaft of 60 inches (150cm) will be sufficient, but you will need to take measurements and calculate the right length for your ‘toon.
If you’re stuck deciding between a shorter and longer shaft version, it’s usually safer to go a little longer.
The typical jon boat will need a trolling motor with a shaft of at least 42 inches, but it’s always best to check the measurements first.
Again, if you’re unsure, it’s better to go for the longer version.
For kayaks, the most common shaft length is 24″ inches.
However, some factors such as the width of your kayak, the type of fishing you’re doing and the weight of your gear will also play a role in determining the ideal shaft length.
Canoes usually need slightly longer shafts than most kayaks. 30 inches or thereabouts. Of course it’s best to measure first, as it varies depending on how high you mount your trolling motor.
The length of your trolling motor’s shaft will be determined by the size and type of your bass boat. However, in most cases it will be 42-45 inches.
Longer Shaft for Rougher Water Conditions
If you use your trolling motor on larger water bodies with a chop and larger waves more common, then it is good to pick a longer shaft.
Choppy waters will move your motor up and down, close to the waterline or even above it. This will result in the loss of thrust and potential damage to the motor’s propeller.
So if you’re not sure which shaft length to choose of the same trolling motor model, pick the longer one. It will be a much safer choice.
Shortening the Existing Shaft
Sometimes you end up with a trolling motor with a shaft that is too long. It may stick out too high, which can be annoying.
What should you do?
It is relatively easy for many popular trolling motor models to shorten the shaft that is too long. Many YouTube videos are showing how this can be done.
It is important to note that such alteration will most likely void your motor’s warranty, so do it only if you have to.
Can you lengthen a trolling motor’s shaft?
Yes, it is possible to lengthen the shaft of your trolling motor, but you should only do so if absolutely necessary. This is because extending the shaft will make the trolling motor less stable and can negatively impact its performance.
If you decide to extend the shaft on your own, bear in mind you could damage the existing shaft as well as other parts of the motor.
This will also likely void your warranty, so it’s always best to consult with the manufacturer or any authorized service center first.
In summary, the length of your trolling motor’s shaft is determined by the type of boat you have and where you want to mount the motor.
Picking the right shaft length is not difficult. Just make sure that you take accurate measurements.
Also, take into account the type of fishing you’re doing and the conditions you typically fish in. If in doubt, always go for a longer shaft – it will be the safer choice.
Frequently Asked Questions
Can a trolling motor shaft be too long?
This is usually not a problem, as a shaft that is too long can always be pulled up or trimmed so that the motor is not too deep under water. If your trolling motor sticks out more than necessary, and you find it annoying, it’s usually possible to shorten your trolling motor’s shaft.
However, we usually advise against it, as you might want to use your trolling motor on a different boat in the future. It’s much harder to make your shaft longer once you shorten it.
Plus, if you alter your trolling motor in any way, you will probably void the warranty.
Can a trolling motor shaft be too short?
If your trolling motor’s shaft is too short, it can result in the propeller not being submerged enough. This can cause loss of thrust and potential damage to the propeller. So if you’re unsure which shaft length to choose, always go for the longer one.