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Chandler
Dec 26, 2019  •  2 min

How to Find Your Shaft Length

If you are looking for an ePropulsion electric outboard for your boat, choosing the correct shaft length is important. If you go too long it would still work but it may lack performance. You will also risk hitting bottom or submerged objects more frequently such as rocks. If you go too short, that’s the worst scenario as you‘re more than likely going to cavitate.

Please note that ePropulsion has a different shaft length measurement from gas-powered outboards. For electric outboards, the shaft length is measured from the top of the clamp bracket to the center of the propeller. For gas outboards, it’s measured from the top of the clamp bracket to the anti-ventilation plate.

As you can see, our XS is close to S from Mercury. Our S is close to L from Mercury. Our L is longer than L from Mercury. See below.

To find the suitable shaft length, the principle is to make sure the top of the propeller is matched to the lowest point of the transom. Hard to put it into practice? Well, in order to get the right shaft length, first, measure the transom height, the length from the top of the boat transom to the bottom of the boat.

After that, you could choose the recommended shaft length based according to the transom height.

For most small dinghies and aluminum boats under 15ft or 4.5m, extra short shaft and short will work, depending on the transom height, some over 40 cm / 15.7 inches, some not.

For boats with the transom height higher than 50 cm / 19.7 inches, a long shaft version is more suitable.

For daysailers and short one-design racing sailboats, it depends on the position of the outboard mount. If you choose Spirit 1.0, we suggest you keep the outboard mount at a lower position so XS will work. That’s because XS takes less space to store inside the cabin.

For daysailers, sports boats and other sailing boats it’s best to measure the distance from the water line to the top of your outboard mount.

It’s always worth checking with your local dealer on which shaft length they recommend for your boat and local conditions. If you still have any questions regarding the shaft length, don’t hesitate to leave a message to our official Facebook.

You could download the technical drawing of ePropulsion outboard here.

14 Comments
David Wutzler
August 7, 2020

Hi – just to clarify, is the recommendation that the top of the prop is 140mm (5.51 inches) below the bottom of the boat?

Unknown member
August 7, 2020

Hi David, to find the suitable shaft length, the principle is to make sure the top of the propeller is matched to the lowest point of the transom. Thank you.

Dale Gillette
January 28, 2021

This article suggests lining up the top of the propeller to the lowest point of the transom. However, in every photo and video on your website that shows the propeller under water, it appears that the top of the propeller is at least 4-5 inches below the lowest point of the transom. Why?

Tom
March 27, 2021

Hi, I would also like clarification please – your manual states the top of the propeller should sit between 100 and 150mm below the lowest point of the hull, but this page suggests 0mm below – could you clarify? For reference, my boat has a 400mm deep transom

Debra Huber
April 21, 2021

Shaft length recommended for a 16 ft Compact Yaught

Jared Jensen
April 28, 2021

This indicates that 0mm is appropriate for faster boats, but for slower boats 2-3″ below the bottom of the boat is better. I doubt it matters a whole lot at the speeds this little motor is going to push a dinghy, and a bigger concern might be keeping the shaft shorter if you beach the dinghy frequently so you can get closer to shore before pulling up the motor.
https://boatbuildercentral.com/support-tutorials/Tutorials/outboard-shaft-lengths-and-transoms.pdf

Fab
June 2, 2021

Hello, may I enquire what would be the right size Navy 6.0 for an IRB (Honwave T-40)? Thank you very much.

Chandler
June 3, 2021

Hi Fab, we’d suggest short shaft Navy for transom height between 400mm – 500mm, and long shaft for transom height higher than 500mm.

Rob
June 15, 2021

Considering ordering the Spirit 1.0 Plus. My transom height is 14″ which meets the 15.7″ max transom height criteria of the Xtra Short Shaft. I have heard complaints that the props is too close to the surface of the water. Looking for any feedback or recommendation as to the shaft length? We do go into the shallows from time to time, so I am trying to avoid the extra 4″ of depth with the Short shaft if possible.

Chandler
June 23, 2021

Hi Rob, we would suggest the Extra Short shaft for your application. Thanks!

Bill
July 10, 2021

I have a square stern canoe with a transom height of 17”….will the XS shaft work? Short shaft seem too long.

Chandler
July 12, 2021

Hi Bill, we would recommend the short shaft for your application. If you are not sure about whether the short or extra short shaft suits you better, you may schedule a test ride with our local dealer by filling up this quick form https://epropulsion.typeform.com/to/cpDJAn

Jamie
September 9, 2021

I have a Walkerbay 8’ will the extra short shaft work? Not sure of the measurements as the dinks in Florida

Chandler
September 9, 2021

Hi, I have googled the Waterbay boat and found this measurement. https://walkerbaydinghies.com/wp-content/uploads/2016/12/WB-8-SPEC-SHEET-2014.pdf
It shows the transom height is around 53cm, which is suitable for the Spirit Long shaft. But it’s better to have your boat measured as well, just in case.

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