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ePropulsion
Sep 30, 2023  •  10 min

Short Shaft Outboard Motors: Everything You Need to Know

Short shaft outboard motors are ideal for small boats including dinghies, tenders, inflatable boats, or sailboats as kicker motors, providing higher power efficiency, and better performances at higher speeds, at lower costs.

However, what is a short shaft outboard motor? How do I know if I need a long or short shaft outboard? How tall should a transom be for a short shaft outboard motor? What happens if you put a long shaft motor on a short shaft boat?

If you are new to the boating world, you could have a long question list about the short shaft outboard motors.

Even experienced boaters can be confused by the short shaft outboard motor lengths, prices, and the modern options available (since the outboard can last really long if you take good care of it).

No worries. This post will explain everything you need to know about short shaft outboard motors to help you make a wise choice, quickly.

Table of content:

Short Shaft Outboard Motors

Short Shaft Outboard Motor 101

Before we get into details, let’s make it clear what a short shaft outboard motor is so that we are on the same page. So how long is a short shaft outboard motor?

As an industry standard, a short shaft combustion outboard motor is 15 inches, a long shaft outboard motor is 20 inches, and an extra long shaft motor is 25 inches.

Combustion Outboard Motor Length OptionsShaft Length Measurement
Short Shaft15”
Long Shaft20”
Extra Long Shaft25”

How do we get this measurement? How to measure a short shaft outboard motor?

Remember that a short shaft outboard motor length is measured from the top of the mounting clamp bracket to the bottom of the anti-ventilation plate (See the diagram below).

Combustion Outboard Motor Length Diagram

Now you may wonder whether the “shaft lengths” measurement varies between different outboard manufacturers (regardless of being assigned the terms short shaft or long shaft).

The answer is NO if you are comparing short shaft outboard motors in the combustion world only.

This makes it easy for you to communicate with different manufacturers.

However, the short shaft outboard motor length measurement is slightly different if you go with electric.

Compared with combustion motors, electric outboard motors tend to have longer shaft lengths:

For example, an extra short shaft electric outboard motor is around 21 inches, a short shaft electric outboard is around 25 inches, and a long shaft length goes to around 30 inches.

Electric Outboard Motor Length OptionsShaft Length Measurement
Extra Short Shaft20”
Short Shaft25”
Long Shaft30”

Also, remember that the short shaft outboard motor length measurement is from the top of the clamp bracket to the center of the propeller (instead of the cavitation plate for combustion outboards).

Electric Outboard Motor Length Diagram

Here is a comparison chart between electric and combustion outboards so you can have a better idea of what shaft length options you may have with each solution.

ComparisonElectric OutboardsCombustion Outboards
Extra Short Shaft Length20.7” (52.5 cm)x
Short Shaft Length24.6” (62.5 cm)15” (38 cm)
Long Shaft Length29.5” (75 cm)20” (51 cm)
Extra Long Shaft Lengthx25” (64 cm)
Ultra Long Shaft Lengthx30” (76 cm)

So which short shaft outboard motor is better for you?

According to our experiences dealing with customer requests over the years, an easy and safe way to decide is always going electric if you want a reliable and quiet short shaft outboard motor solution for your boat.

Further Reading: When you need a small outboard, do you choose electric or petrol?

Long Shaft Versus Short Shaft Outboard Motor

Now that we’ve understood the differences between a long and short shaft outboard motor, it’s time to decide which one is better for you.

So how do I know if my boat motor is long or short shaft? What’s better long shaft or short shaft outboard? When do you want a short shaft outboard motor vs the long option?

Essentially, it’s all about your transom height.

Generally speaking, a short shaft outboard motor is built to hang on a 15” high transom, and a long shaft is designed for a 20” transom.

Apparently, if you put a short shaft outboard motor on a long shaft boat, the propeller will not extend deep enough, causing overheating and cavitation problems (when the propeller is out of water), and thus power loss.

By contrast, if you put a long shaft motor on a short shaft boat, the prop will be too deep, causing extra drags and making the bow rise with an upward thrust that loses efficiency. In this case, it would be way more fun to have a short shaft outboard motor instead.

Does a short shaft outboard motor make that much of a difference?

Theoretically, you can never get full speed out of your motor, whether it’s too deep or shallow in the water.

If you are only looking for trolling speed to help go in and out of the slip, it’s not a big problem whether you go with longer or shorter shaft outboard motors.

However, if you are trying to go faster (than 4-5 mph), a proper shaft length will make a HUGE difference.

Also, don’t forget that a short shaft outboard motor means a more compact design and less weight, which makes it easier to store and transport.

Do I need a long or short shaft outboard motor?

Generally speaking, if you own a small boat, you will likely need a short shaft outboard motor to make the best use of it.

A good way to find your best short shaft outboard motor is to check the manufacturer’s buying guide with tips to determine the proper shaft length for outboard motors.

Most outboard manufacturers will provide a guide based upon measurement. For example, ePropulsion has released a shaft length guide that allows you to calculate the exact shaft length needed for your specific boat so that you can choose the long or short shaft outboard motor with confidence.

Best Short Shaft Outboard Motors (with Prices)

Looking for the best short shaft outboard motor for sale on the market?

Among the seemly endless manufacturers who make short shaft outboard motors, we’ve selected the top 3 models with the latest technology, competitive prices, and thousands of happy customers worldwide.

To help you make an easy decision, the recommendation list only covers the most popular options for short shaft outboard motors, including the 3 HP, 6 HP, and 9.9 HP models.

If you have any other specific needs or requests, leave a comment below and I will try to provide a short shaft outboard motor solution tailored to your needs.

Editor’s Note: The price indicated below is just for your reference and can be different depending on your selection of the batteries, accessories, and location.

#1. 3 HP Short Shaft Outboard Motor: Spirit 1.0 Plus

3HP Short Shaft Outboard Motor

If you are looking for a 3 HP outboard motor short shaft with tiller, look no further than Spirit 1.0 Plus.

Spirit 1.0 Plus features a 20.7 inch shaft with a compact design for easy storage and transportation.

This 3 HP short shaft outboard motor is made for dinghies, fishing boats, sailboats, tenders and other small boats. It’s lightweight and reliable with a built-in tiller for easy maneuverability.

More than that, this short shaft electric outboard motor promises you a cleaner and quieter ride than ever. It’s literally just you and nature on the boat. No smell, no noise, and no pollution.

The integrated lithium battery is designed for long range, delivering impressive performances whether it’s intended for slow trolling or some higher speed fun:

Power (W)Speed (mph / kph)Runtime (hh:mm)Range (mile / km)
352.2 / 3.512:2580 / 129
652.7 / 4.319:3553 / 85.3
1253.5 / 5.610:0035 / 56
2504.4 / 7.15:0022 / 35.5
5005.3 / 8.52:3013.3 / 21.3
7505.7 / 9.21:409.5 / 15.3
10006.2 / 101:157.8 / 12.5
* Data is collected on a 12-foot aluminum boat with one person and one Spirit battery Plus in calm lake water. **Remote control is also available with this short shaft outboard by adding a wheel and remote.

#2. 6 HP Short Shaft Outboard Motor: Navy 3.0 Evo

6 HP Short Shaft Outboard Motor

This 6 HP short shaft outboard motor gives you some more juice for extended range and time on the water.

Its short shaft is measured 24.6 inches long from the mounting bracket to the center of its propeller.

The short shaft outboard provides efficient and clean power for aluminum fishing boats, dinghies, daysailers and cruising sailboats, suitable for both saltwater and freshwater.

Besides its electric virtue of being clean and quiet (with all information available through a digital display), its direct drive technology makes this short shaft outboard motor nearly maintenance-free, saving you a lot of time and money in the long run.

It offers four types of controls to cover your various boating needs and installation requirements, including tiller, top mount control, side mount control, and dual control.

Check out the short shaft outboard motor performances on a 12-foot aluminum boat with one person, powered by one E80 battery:

Power (Watt)Speed (mph / kph)Running Time (hh:mm)Range (mile / km)
3003.7 / 613:2049.3 / 79.3
5504.7 / 7.57:2535 / 56.3
10005.3 / 8.64:0021.2 / 34.1
15006 / 9.72:4016 / 25.7
20006.3 / 10.22:0012.6 / 20.4
25008 / 12.81:3512.7 / 20.5
300010.2 / 16.41:2013.6 / 21.9

If you are a sailor, you will love this short shaft outboard motor since it features an advanced hydrogeneration function that allows you to collect electricity from wind and water.

#3. 9.9 HP Short Shaft Outboard Motor: Navy 6.0 Evo

9.9 HP Short Shaft Outboard Motor

Still want more power with your short shaft outboard motor? Check out the 9.9 HP Navy 6.0 Evo.

This 9.9 HP short shaft outboard motor is suitable for tenders, pontoon boats, bass boats. Daysailers, commercial boats, and motorboats under 30 ft.

With one charge, you can go 40 miles with Navy 6.0 Evo, or go fishing all day long at trolling speed:

Power (Watt)Speed (mph / kph)Running Time (hh:mm)Range (mile / km)
5004 / 6.518:0072 / 116
10008-May9:0045 / 72
20006.7 / 10.84:3030.2 / 48.6
300013-Aug3:0024 / 39
400011.5 / 18.52:1525.9 / 41.7
500013.5 / 21.81:5024.7 / 39.8
600015 / 24.31:3022.5 / 36.5

*Data collected on the same boat as Navy 3.0 Evo to help you compare.

Other than that, the 9.9 HP short shaft outboard Navy 6.0 Evo is basically the same as the 6 HP model. That’s to say, you will get all the benefits and a larger motor to provide more range and run time.

Short Shaft Outboard Motor on Long Shaft Boat

It’s highly possible that you get a short shaft outboard motor for a long shaft boat (or the other way around).

After all, the boat models are nearly endless while the shaft length option is limited.

Or you just own a spare short shaft outboard motor that’s ready for use, like the following:

I ran into a big problem when I bought a skiff with a 20″ transom. I have a short shaft outboard that I want to keep. Does anyone have any suggestions on how I can make this work?

No worries. There are a lot of easy ways you can try to make the short shaft outboard work.

Solution #1. The easiest way is to trade the short shaft outboard motor for a longer one, although it takes time.

Solution #2. you can always mount a jack plate to adjust the transom height. That way, you can put an outboard with a longer or shorter shaft on your boat (just adjust the jackplate to level the motor with your boat).

Solution #3. Otherwise, you might check with a dealer or other local O/B mechanic about the expense and availability of changing out the short shaft to a long one and adding mid housing extension.

There would also be exhaust chamber, shift shaft, and water tube length concerns. The modification can also void the manufacturer’s warranty of your short shaft outboard motor.

Solution #4. Some experienced boaters may also try lowering the transom by cutting a few inches off to make it work for your existing short shaft outboard motor.

If you decide to cut down your transom, don’t forget to reinforce the transom afterward.

Join the discussion!

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