Tedgix K4C vs K4S: Which Electric Paddle Board and Kayak Motor Fits You?

Quick answer: Choose the Tedgix K4C Cruise if you want a light 400W motor for relaxed cruising on a paddle board or kayak. Choose the Tedgix K4S Sport if you carry more weight, paddle with a second rider, or push into wind and longer distances: it has 1500W and up to 47 lbs of thrust. Both slide into a standard US fin box, run on a separate waterproof battery, and come with a wireless remote.

Electric fin motors are one of the most popular upgrades we carry this year. Here is how the two Tedgix K4 motors compare, using Tedgix's published figures.

What is an electric fin motor?

An electric fin motor is a small propeller unit that mounts in the fin box under your paddle board or kayak, in place of the center fin. A waterproof battery rides on the deck, a cable connects the two, and a wireless remote in your hand sets the speed. There is no gas, no outboard bracket, and no change to the board itself: take the motor out and you have your regular board back.

Tedgix K4C vs K4S: the key differences

Tedgix K4C Cruise

• Power: 400W brushless motor
• Thrust: 10 kg (22 lbs)
• Speed: up to 6 mph (9.6 km/h), cruising at 3 to 4 mph
• Weight: 3.4 lbs (1,535 g) with cable
• Mount: slide-in US-BOX adapter, included
• Batteries: Tedgix B4 (423 Wh) or B8 (808 Wh), sold separately
• Best for: solo cruising, shoreline tours, a lift home at the end of the day

Tedgix K4S Sport

• Power: 1500W brushless motor
• Thrust: 21.5 kg (47 lbs)
• Speed: up to 9.3 mph, cruising at 3.5 to 5 mph
• Weight: 3.9 lbs (1.78 kg) with cables
• Mount: quick-release fin box base, included
• Battery: Tedgix B15 (1526 Wh, 48V), sold separately
• Best for: fishing kayaks, two riders, inflatable boats, headwinds and longer open-water runs

How fast does an electric paddle board motor go?

Tedgix rates the K4C at up to 6 mph and the K4S at up to 9.3 mph. Most of your time will be spent at a cruise: 3 to 4 mph on the K4C and 3.5 to 5 mph on the K4S. Real speed depends on your board or kayak, total weight, wind, current and battery charge, so treat top speed as a ceiling, not a promise.

How long does the battery last?

Runtime depends far more on speed than on anything else. Tedgix's figures:

• K4C with the B4 (423 Wh): about 5 hours at cruising speed, about 1.3 hours at top speed
• K4C with the B8 (808 Wh): about 8.75 hours at cruising speed, about 2 hours at top speed
• K4S with the B15 (1526 Wh): about 14 hours in economy mode, 1.9 hours at half throttle, 1 hour at full throttle

At a 3.1 mph cruise, 5 hours on the B4 works out to roughly 15 miles in calm water by our math. Wind, current and extra weight shorten that, so plan your route with a margin and keep a paddle on board.

Which batteries and chargers work with each motor?

The two motors use different voltages, so their batteries are not interchangeable.

• K4C: runs on the K4 batteries (B4 or B8 Pro). They charge from a standard USB-C PD charger or the Tedgix K4 fast charger, and neither charger is included. The B4 also works as a USB-C power bank for a phone or camera.
• K4S: runs only on the 48V B15 battery. It charges with the Tedgix 440W standard or 819W fast charger, sold separately. Its USB-C port puts out up to 100W for devices but does not charge the battery. Do not use the K4C charger on the B15.

How do you install a fin motor?

1. Remove the center fin from your board or kayak.
2. Slide the motor's mount into the US fin box: the US-BOX adapter on the K4C, the quick-release base on the K4S.
3. Drop in the screw and plate and finger-tighten, the same way you fit a center fin.
4. Secure the battery on deck, connect the motor cable, and pair the remote.

Tedgix and NIXY put the K4C install at under 5 minutes. To pack up, reverse the steps and slide the motor out.

Can you use a fin motor in saltwater?

Yes. Both motors are rated for fresh and saltwater. After every saltwater session, rinse the motor, propeller, mount and connectors with fresh water, wipe them down and let everything air-dry before storage. The K4C remote is IP68 rated, so it is sealed against submersion.

Which motor should you choose?

• Solo paddler on calm lakes, bays and rivers: K4C with the B4 for half days or the B8 for full days.
• Two riders, a kid, or a dog on a big board: K4S. The extra thrust keeps the cruise steady under load.
• Fishing kayak with gear, or long open-water crossings: K4S with the B15.
• Travel and light packing: K4C. It is the lighter motor and pairs with the lighter B4 battery.

Going deeper? Read our guides to adding a motor to a paddle board and putting an electric motor on an inflatable kayak, or browse every motor, battery and part in our electric motors collection.

Frequently asked questions

Is the battery included with Tedgix motors?

No. Both motors ship without a battery. The K4C needs a B4 or B8, and the K4S needs the B15. You can add one on the K4C and K4S product pages.

Can I use K4C batteries on the K4S?

No. The K4S runs on a 48V battery and the K4C batteries are a different voltage. Use the B15 with the K4S and the B4 or B8 with the K4C.

Can I take a motor battery on a plane?

No. Tedgix batteries are 423 Wh to 1526 Wh, and the FAA forbids lithium-ion batteries over 160 Wh on passenger aircraft, in carry-on or checked bags (FAA PackSafe, checked October 2026). Plan to drive with your battery, or charge one at your destination if you have one there.

Do I need to register a paddle board or kayak with a motor?

In California, any boat or vessel with a motor, no matter how small, must be registered with the DMV, and since January 1, 2025 every operator of a motorized vessel needs a California Boater Card (California DMV and California State Parks, checked October 2026). Other states set their own rules, and some lakes limit or ban motors, so check your state boating agency and your launch site before your first run.

What warranty do Tedgix motors have?

Both motors carry a 1-year Tedgix warranty. NIXY handles your order and helps with product questions.