Last Updated on June 15, 2022
Generally speaking, a 12v 55lbs thrust 42″ shaft trolling motor will work on most boats. However, there are several exceptions.
Trolling motor size primarily depends on the size of your boat (weight and height) and mounting location (bow or transom).
I’ve found myself in situations where I’ve had the wrong size trolling motor and it’s caused a lot of frustration and headache.
At Anglers.com, we want your fishing trips to be as fun as possible, which is why we’re condensing our years of trial and error to answer the question:
What size trolling motor do I need?
In this guide, you’ll find out!
What Size Trolling Motor Do I Need For My Boat?
When discussing trolling motor size, we’re primarily talking about the shaft length and the pounds of thrust.
The shaft length is determined by the distance from the top of your boat to the waterline.
It would be best if you had a long enough shaft to hold the lower unit about one foot below the water’s surface, without too much shaft sticking up so that it gets in the way while you’re fishing.
Bow Mount Trolling Motor Size Guide
|Top of Bow To Water’s Surface||Shaft Length|
|0″ – 16″||36″|
|16″ – 22″||42″|
|22″ – 28″||48″ – 52″|
|28″ – 34″||52″ – 62″|
Transom Mount Trolling Motor Shaft Length Guide
|Top of Transom To Water’s Surface||Shaft Length|
|0″ – 12″||30″|
|12″ – 18″||36″|
|18″ – 24″||42″|
The trolling motor thrust you need is determined by how big your boat is and how fast you wish to go while fishing.
If you have a trolling motor that will propel you four miles per hour, that’s a quick electric trolling motor.
Most professional anglers are thrilled with a trolling motor with a 4-5mph top speed.
Trolling Motor Thrust Guide
|Fully Loaded Boat Weight||Boat Length||Minimum Pounds of Thrust||Recommended Pounds of Thrust|
|1500lbs or less||14′ – 16′||30lbs||55lbs|
|2000lbs||16′ – 18′||40lbs||60lbs|
|2500lbs||18′ – 20′||50lbs||70lbs|
|3000lbs||20′ – 22′||60lbs||80lbs|
|3500lbs||22′ – 24′||70lbs||90lbs|
|4000lbs||24′ – 26′||80lbs||100lbs|
|5000lbs||28′ – 30′||100lbs||120lbs|
|5500lbs||30′ +||110lbs +||120lbs +|
You always want more thrust than you’ll need for days when battling the wind and currents. That’s why I don’t recommend going with the minimum thrust.
It’s a common rule of thumb that you only need 5lbs of thrust for every 200 lbs, but that doesn’t factor in the wind or current, so I prefer to up that a little, so I know my trolling motor can handle any rough water I encounter.
Let’s move on to selecting a trolling motor sized based on the boat you use.
Kayak Trolling Motor Size
Choosing a trolling motor for a kayak is pretty simple. It depends on whether you want a bow mount or transom mount and how much thrust you want.
A typical trolling motor shaft length is 36″ for a kayak. Because kayaks sit low in the water, you don’t need a longer shaft and can probably get by with a 30″ shaft.
I’ve used a longer shaft on my kayak, and it has only caused minor frustrations, but I would prefer to have the shorter shaft.
For a kayak trolling motor, you don’t need more than 55lbs of thrust. This much thrust will push just about any kayak as fast as possible.
I have a heavy fishing kayak with a trolling motor with 45lbs of thrust, and on a calm morning, I can reach four mph.
The size should be a 12-volt 36″ shaft on a 55lb trolling motor like a Motorguide Xi3, whether it’s a bow or transom mount.
If you need help mounting a trolling motor to your kayak, check out our how-to mount a trolling motor on a kayak guide!
Jon Boat/Dingy Trolling Motor Size
Jon boats and dingies come in various sizes, so we’re going to start with the smaller sizes and work our way up. You’ll notice that these boats need a larger trolling motor than a kayak because they’re less aerodynamic and heavier.
With a small boat, you’ll likely be using a transom mount motor, but larger Jon boats come with the option of a bow mount trolling motor.
10′ – 12′
You can get by with a trolling motor similar in size to a kayak trolling motor when you’re in a small Jon boat or dingy. However, I would recommend a longer shaft.
The best trolling motor for a small Jon boat is a 12v 42″ shaft with 55lbs of thrust.
If you own a medium-sized Jon boat or dingy, you’ll need to step up the size of your trolling motor. I wouldn’t go any less than a 12v 42″ shaft with a 55lb thrust trolling motor. Ideally, you could step up to a 24-volt 46″ shaft with 62+ pounds of thrust.
I wouldn’t recommend a trolling motor that requires more than 24v because then your boat’s weight capacity will be taken up by the batteries.
By now, you know larger boats need a larger trolling motor. So for an 18′ or larger Jon boat, I recommend a minimum of a 24-volt system 52″ shaft with 72lbs of thrust.
This will ensure you have plenty of power to control your boat if the wind picks up.
Bass Boat Trolling Motor Size
Bass boats are more aerodynamic and lighter than Jon boats, but they often serve a different purpose and need a larger trolling motor.
The primary reason for this is that most bass boats will have a bow-mounted trolling motor, and bass anglers want more than enough power for the windy days or when they’re fishing in strong currents.
16′ – 18′
Starting where we left off for Jon boats, I recommend a 24v 52″ shaft with 72lbs of thrust for a 16 to an 18-foot bass boat.
Depending on how high your boat sits out of the water, you might need to purchase a shorter or longer shaft, but a trolling motor with similar specs as the ones listed above should be adequate.
18′ – 20′
If your boat is in the 18′ – 20′ range, you can begin thinking about a 36-volt system with more power. However, a 24v trolling motor will still have enough power to handle just about any situation.
The ideal trolling motor for this size of a bass boat is a 24-volt 52″- 60″ shaft with 80lbs of thrust. Trolling motors with more than 80lbs of thrust tend to need 36-volts.
For 20′ and larger bass boats, it’s best to have a 36v 52″- 60″ shaft with 100lbs of thrust. These boats have more room for deep cycle batteries than smaller boats, plus the extra power is nice to help better control the boat.
Pontoon Boat Trolling Motor Size
Pontoons are a special case. They’re a large boat that catches a lot of wind, but they’re lightweight. So they don’t require as powerful of a trolling motor as one might think. They do, however, need a long shaft.
16′ – 18′
For pontoons in this size range, Minn Kota makes a couple of options, a 12v 48″ shaft and 55lb thrust with a foot control, which I think is a little small.
They also manufacture a 12v 52″ shaft and 55lbs of thrust with hand tiller control, which I believe is the better choice, even though it’s hand control and not incredibly powerful.
Pontoons 18′ – 20′ need a more powerful trolling; that’s why I would go with a 24v 52″ shaft and 70lbs of thrust with a tiller handle. You have room for the additional battery, and you might need the extra power on windy days.
You need a powerful motor when you get to pontoon boats this large. Especially if you’re asking, “what size trolling motor for a 24′ pontoon boat?”
Since they are similar in size and weight to 18′ – 20′ pontoons, I recommend a minimum of 24v 52″ shaft and 70lbs of thrust, but if you can, I would go with more thrust, but most trolling motor manufacturers stop around 70lbs for pontoon trolling motors.
What Size Trolling Motor Battery Do I Need?
The size of your trolling motor battery will determine your trolling motor’s power and run time. The power is measured in volts. 12-volt batteries are the least powerful, while 36-volt batteries are the most powerful.
You can also run the batteries in series, so two 12v batteries would equal a 24v battery, but your capacity would be the same.
To lengthen your motor’s run time, you will need to buy a battery with an increased Ampere hour rating.
Picking the right trolling motor battery can make the difference between having enough power or running out of juice.
Choosing the right trolling motor can be the difference between a good day of fishing or fighting the wind all day instead of fishing.
That’s why it’s crucial to have the correct shaft length and power for your boat size.
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If you have any other questions regarding “what size trolling motor do I need?” feel free to drop them in the comments below!