What Size Motor Should You Get For a Jon Boat?


14 foot Jon boat with 15hp mounted outboard motor

The humble Jon boat is such a versatile watercraft that it can be rowed, paddled, punted (poled) and fitted with a motor. But if you buy a Jon boat without an outboard motor how do you know what size motor it needs?  Let us help.

The size of the motor that should be mounted on a Jon boat will vary with the size of the boat and its weight capacity. For Jon boats between 8 foot and 16 foot, 8 hp – 20 hp motors will offer more than enough power to push the boat upstream, achieve a respectable speed and get the boat on plane. 18 + foot Jon boats can usually take a 20 – 25 hp outboard motor.

What size of motor is best for a Jon boat?

The size of motor you choose for a Jon boat will be dependent on the size of the boat. A trolling motor is often the first choice for a Jon boat owner to mount on his/her because it is small and light and will provide more than enough power for upstream use.

However, some Jon boat owners will mount much larger outboards if their boat can handle the extra weight at the back. More powerful outboard motors are often needed as trolling motors can make it difficult to get a Jon boat on plane and it may even cause it to start porpoising.

Although a Jon boat can be pushed at speed with a simple trolling motor, as the boat gets bigger a trolling motor will tend to lack in the necessary thrust to get the most out of your boat.

A 3 hp trolling motor will provide enough power and thrust to get a Jon boat moving upstream but it will not provide speed.

Below is a list of the best size hp motors based on Jon boat length:

  • 8 foot – 3 – 8 hp motor.
  • 10 foot – 3 – 10 hp motor.
  • 12 foot – 10 – 15 hp motor.
  • 14 foot -15 hp motor.
  • 16 foot – 15 – 20 hp motor.
  • 18 foot – 18 – 20 hp motor.
  • 20+ foot – 20 – 25  hp motor.

The above list is a quick and simple guide as not all boats are the same. For example, you can easily find that one particular 14′ foot Jon boat can take a 20 hp outboard motor while a different 14′ model can only handle a 15 hp, even though they are both made by the same manufacturer!

It seems that the gauge of aluminum used in the boat’s construction can affect the size of the motor that can be mounted on the Jon.

Trolling vs outboard

Trolling motors are great for small Jon boats. Their small size and incredible lightweight nature means they don’t take up a lot of space on the boat and won’t weight down the stern. Unfortunately though they aren’t very powerful.

Trolling motors will usually offer just enough power to push a Jon a boat upstream but it won’t offer you much speed and it is doubtful you will get the boat on plane.

The extra thrust offered by a larger outboard motor will mean it is easier to achieve good speeds on a Jon and get the boat on plane for that extra ultra smooth fast cruising.

Electric vs gas

If you plan to go with a trolling motor then you will have the choice between gas-powered and battery-powered.

Gas motors are by far the most popular choice because they offer more thrust than their electric counterparts. However, electric motors have their place and you should not just dismiss them because you an “outboard gearhead”.

Electric motors are lighter and don’t require a gas tank on the boat. The are also a lot quieter which many anglers and hunters like. Gas motors tend to be noisy and scare away fish and prey alike.

An electric trolling motor will offer enough power to move the boat into your chosen fishing or hunting waters and then, via the use of paddle or pole, you can get into position using a more stealthy approach.

Thrust vs boat weight

A heavier Jon boat will require a bigger hp engine to provide the thrust needed to propel the boat. So many hunters, who take lots of gear and dogs, choose bigger engines. Likewise those who use their Jon boats for boat camping will also tend to opt for more power as they laden their boat with passengers, gear and supplies.

To work out the weight capacity of your Jon boat, if it has no plate, read this.

To ensure your Jon boat has the needed thrust to provide you with power and speed it is recommend you use a motor with 5 lb of thrust for every 200 lb gross boat weight.

Important word about shaft length

When choosing the correct motor for a Jon boat it should not just be about the size of the engine. Shaft length plays an important role as well.

Because Jon boats have small transoms, and low freeboard (like many shallow water boats) you will most likely want a motor with a shorter shaft.

Why do you need a shorter shaft length on the motor you mount on a Jon boat? Because if you don’t you will regret it especially when you give it some throttle and attempt to build up speed.

The length of the shaft on an outboard motor affects the position of the prop in the water. The position of the prop is important because it not only propels the boat forward but it greatly affects the stability of the boat as it moves in the water.

You should get a motor with a shaft length that matches the length of your transom.

To correctly measure your transom, to determine what shaft length you need for your specific Jon boat, use a standard measuring tape to measure from the top of the transom (the rear of the boat) to its bottom most part. Take this measurement in the middle of the boat along its beam (width wise).

The length of the shaft on the motor you plan to mount on that boat should match the measurement you just took. In other words, the outboard motor’s shaft length should be equal to the length of your boat’s transom.

This is not an exact science. Being an inch off either way is no big deal and will have very little, if any, effect on the boat’s performance. However, if it is several inches off then you could run into problems on the water.

As a Jon boat has a short transom, a shorter shaft length outboard is better. Of course there are exceptions to this rule  but to be on the safe side I’d just stick to a shorter shaft.

There is also a major disadvantage of using a longer shaft outboard motor – it increases the draft of the boat.

The whole point of using a Jon boat is to take advantage of its shallow draft. When you add extra length at its base you increase its draft, essentially changing it from a shallow draft boat into something more akin to a shoal draft boat.

To read more about shallow draft read this article and to learn about shoal draft read this article.

You can also learn about measuring the whole Jon boat properly here.

How to measure your transom for shaft length (video)

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