Shaft Length Guide
Selecting the proper shaft length is critical. You want to make sure the motor's shaft is long enough to keep the propeller submerged in varying water conditions, but not so long that it catches on the bottom or is a hassle to stow.
Bow Mount Shaft Length
Proper shaft length selection is more critical with bow mount motors (as compared to transom mount). Bow-to-water distances tend to vary more from boat to boat, and the bow moves much more on the water than the transom. As such, it's important to make sure you select the proper shaft length. Start by measuring the distance from the horizontal mounting point on the bow to the waterline, then add 20" to this measurement. Generally, you will want a shaft length that is equal to or greater than this sum, but not less. The following factors may be further considerations:
If you frequently fish in rough waters: Then add 5" to the recommended lengths below. This will help the propeller stay submerged despite the additional deck bob of choppy or windy waters.
If steering a hand controlled motor standing up: Then add 12" to the recommended transom lengths below. This will make it easier and more comfortable to steer by bringing the motor tiller higher up.
Transom Mount Shaft Length
Shaft length on transom mount motors is less critical than on bow mount motors, but is still important to double-check.
A Few Rules to Remember
Submersion Rule: You'll want the top of the motor submerged at LEAST 12" under the water to ensure adequate power and to prevent noisy cavitation which will scare fish. The charts above will help you determine what shaft length achieves this (given different distances to the water, the shaft portion above the mount, etc) but it's still a good idea to keep this 12" figure in mind.
Always Go Long: If you're struggling to decide between two lengths, pick the longer one. If the shaft ends up being a bit too long, you can always adjust the shaft depth upward with the depth collar adjustment found on nearly all trolling motors. But if you pick a shaft that's too short, you're simply out of luck.
How the Shaft is Measured
If you're trying to determine how long your existing shaft is - or take measurements on your own boat - it's helpful to know exactly how the shaft is measured. Shaft measurements are taken from the base of the motor head to top of the propeller housing, as seen below:
Grab our FREE Trolling Motor Buyer's Guide and check out all this great information:
"After BassPro couldn't answer my question, I called TrollingMotors.net. The representative was really knowledgeable and answered my question right away! These guys definitely know their stuff and I'd recommend them for any major motor investment to ensure you get the right equipment."
- Anthony G., Kingsland, TX
"TrollingMotors.net was the most informative trolling motor site I found online! When I had questions the site didn't cover, their knowledgeable staff was friendly and helpful. If you're looking to buy a motor - especially a larger one - I would recommend these guys as they will definitely take care of you."
- Jason B., Lake Charles, TX
"The personal service provided was fantastic. They responded very quickly to my emails and phone calls. The order was delivered faster than expected. I will definitely (and already have) told others that this is the only place to go for trolling motors."
- Alan W., Metairie, LA
"I'm so happy I bought from TrollingMotors.net. Not only did they have the motor I was looking for, but I also saved a lot of money."
- David S., Okeechobee, FL
"My $1,500 Terrova 80 i-Pilot purchase was a big investment so I was a little nervous ordering my motor online, but I'm sure glad I chose TrollingMotors.net! When a UPS error delayed delivery, TrollingMotors.net ended up sending another motor to me so I'd have it in time for my tournament."
- Rusty H., East Sparta, OH
"TrollingMotors.net was extremely helpful when UPS damaged my Minn Kota Riptide trolling motor. They arranged for replacement parts to be sent out to me immediately - at no cost - and were very prompt with and follow-up calls and emails. I've been recommending TrollingMotors.net."