Looking for a 10 hp electric outboard motor usually means one of two things: you have a petrol engine of that size and want to know what replaces it, or you have found trolling motor listings quoted in pounds of thrust and cannot work out how that compares to horsepower. Both questions lead to the same answer, and it is not a single number.
This page gives you the working conversion we use when advising customers: thrust in pounds, motor power in watts, and an approximate horsepower equivalent. It also gives you the part most conversion charts leave out — which boat each step of the scale actually suits.
One thing before you read the numbers. Everything below is either a confirmed figure from a motor we sell, or a working rule we apply when advising customers, or an estimate. They are labelled as such. Where we do not have a confirmed number — and there are two on this page — we say so instead of guessing. If you would rather start from the full model list, the electric outboard motor range page has every model on one screen.
lb and hp measure different things
Horsepower is a rate of doing work. On a petrol outboard it is measured at the propeller shaft, under load, with a gearcase in between. Pounds of thrust is a force, measured by holding the motor still on a test rig and pulling against a scale. One describes how fast a motor can push; the other describes how hard it can push at zero speed. They are not the same quantity, so no formula converts one into the other exactly.
If that sounds like splitting hairs, consider two petrol engines of the same horsepower with different gearcase ratios and prop pitches. They produce different thrust at trolling speed. Consider two electric motors with the same quoted thrust and different propellers: they reach different top speeds. The mismatch is real, not academic. The lb convention itself comes from the American trolling motor market, where motors have always been sold by thrust rather than by power, which is why a European buyer moving off a 9.9 hp engine meets a number in pounds instead of watts.
Electric motors do have one characteristic that matters here. They produce maximum torque from a standstill, while a petrol engine has to reach a few thousand revolutions before it makes useful power. Pushing a heavy boat away from a jetty, holding a course into wind, or creeping along a weed line at 2 km/h — the electric motor feels stronger than its rated horsepower suggests, because at those speeds the petrol engine is barely above idle.
So the honest approach is to compare at the speeds these motors actually run at, match thrust against the drag of a displacement hull, and give you a range rather than a false precision. That is what the table below does.
The conversion table
The left column is the number you will see on a product page. The middle columns convert it into power and into a petrol equivalent. The right-hand columns tell you what kind of boat that thrust is intended for. Rows marked with a model name are motors we sell; their power figures are confirmed peak power.
| Thrust | Peak power | Petrol equivalent (approximate) | Recommended boat length | Maximum current |
|---|---|---|---|---|
| 30 lb | varies by model | about 1 hp | kayaks and canoes | varies by model |
| 40 lb | varies by model | about 1.5 hp | kayaks and canoes | varies by model |
| 55 lb | varies by model | about 2 hp | tenders under 3 m | varies by model |
| 75 lb — P150 | 850 W | about 1.7 hp | up to 3 m | 65 A |
| 85 lb — P200 | 960 W | about 2 hp | 3–4 m | 80 A |
| 85–130 lb — P360 | 960–1800 W | about 2–3.5 hp | 3–5 m | 80 A |
| 130 lb — P300 | 1800 W | about 3.5 hp | 3–5 m | 75 A |
| 150 lb — P350 | 2100 W | about 4 hp | 3–5 m | 45 A |
| 220 lb — P400 | 3000 W | about 6 hp | 4–7 m | 65 A |
| 560 lb — P500 | 2200–8000 W, depending on pack voltage | about 4.5–12 hp | 4–7 m | 90–155 A |
How to read it. The petrol equivalent column is an estimate, not a specification. It is built on the working rule of roughly 500 W of peak electrical input per horsepower of petrol outboard, applied to a displacement hull moving at displacement speed. On that rule a 3000 W motor reads as 6 hp and an 8000 W motor as 12 hp. The boat-length column is the manufacturer’s recommended range for each model, assuming a laden boat; hull shape matters more than length, so a flat-bottomed aluminium boat of 4 m needs less thrust than a deep-keel sailboat of the same length.
The P500 row is the only one where the numbers depend on the pack you fit: 2200 W on a 24 V pack, 7500 W on 48 V, 8000 W on 72 V, with thrust rising alongside to 160 lb, 525 lb and 560 lb.
If you already know roughly how much thrust you need, these are the models that map onto it:
- P150 – 75 lb, 850 W, 12 V
- P200 – 85 lb, 960 W, 12 V
- P250 – 55 lb at 12 V / 105 lb at 24 V
- P300 – 130 lb, 1800 W, 24 V
- P350 – 150 lb, 2100 W, 48 V
- P360 – 85 lb at 12 V / 130 lb at 24 V
- P400 – 220 lb, 3000 W, 48 V
- P500 – up to 560 lb, 8000 W
How to size by boat type
Boat type narrows the range faster than any table. These are the five categories customers actually ask about, with the thrust band that works and the reason it works.
Inflatable and PVC dinghies, 2.4–3.0 m. Inflatable tubes are draggy: a lightly loaded 2.6 m tender needs more thrust than its weight suggests, because the tubes sit deep and push water aside. 55–75 lb is the useful band. The P150 at 75 lb on 12 V is the usual pick, and in most cases it is more thrust than the tender strictly needs — which is fine, because reserve thrust is what gets you home against a headwind.
Aluminium open boats, 3.0–3.6 m. Light for their length, but they carry more crew and gear than a tender. 70–85 lb covers the range. The P200 at 85 lb is the model we recommend most often for this size, and it is also our best seller for first-time buyers moving off a small petrol engine.
Fibreglass fishing boats, 3.6–4.5 m. Heavier hull, more windage, more weight in batteries and gear. 85–150 lb. Choose by loaded weight: under about 800 kg total, the P300 at 130 lb is enough; a heavily loaded 4.2 m hull wants the P350 at 150 lb.
Sailboat auxiliary, 22–28 ft. A displacement hull with a small propeller aperture. You need thrust to punch through chop on the way in and out of a mooring, not speed. 85–130 lb is the band for most boats in this size, which puts the P200 and P300 in the frame. Above that, a 28 ft boat with a full keel is genuinely at the edge of what a transom-mounted trolling motor should be asked to do, and we will say so rather than sell you one.
Kayaks and canoes. 30–55 lb, and the real constraint is mounting and weight distribution rather than thrust. A motor plus battery at the stern of a 4 m kayak changes the trim noticeably; keep the battery forward if you can. The P150 is the smallest model we make and is the only one that belongs on a boat this light.
If your boat does not fit any of these — a 4.8 m rib, a wide-beam pontoon, a heavy workboat — the P400 at 220 lb is the general answer. It reads 6 hp, and it is still what we point at when someone is coming off a 9.9 hp petrol four-stroke, because those boats are 4–5 m displacement hulls.
Choosing voltage: 12V / 24V / 48V
Voltage is not a power rating. It is a wiring decision that follows from the thrust you need, and getting it wrong is the most expensive mistake on this page because it usually means buying batteries twice.
12 V. One battery, one charger, the simplest installation there is, and the setup most people already own. It covers the lower half of the range — up to about 85 lb in our line. If your boat is under 3.6 m and you want to keep the electrical system simple, stay on 12 V.
24 V. Two 12 V batteries in series. Doubling the voltage halves the current for the same power, which means thinner cables, less heat and less voltage drop over the length of the boat — the reason the mid-range motors are 24 V rather than 12 V. Two batteries also give you capacity for a longer day. It covers the 120–150 lb band. If you are not ready to commit to a voltage yet, the P250 and the P360 are the two models we make that run on either 12 V or 24 V — 1400 W and 1800 W respectively.
48 V. Four 12 V batteries, or a dedicated 48 V pack. This is where the high-thrust motors live, and it is not a casual upgrade: you want a proper fuse, correctly sized cable, and a charger that matches the pack. The P350 and P400 both run on 48 V.
The P500 sits outside this scale entirely at 20–72 V. It is a different class of machine, not a drop-in for a 12 V boat, and it is currently out of stock.
Whatever you choose, the rule is absolute: never connect a motor to a higher voltage than it is rated for. A 12 V motor on a 24 V bank will be destroyed, usually within seconds, and that is not a warranty matter. If you are moving from one voltage to another, read up on sizing and wiring a battery before you buy anything.
What “6 hp equivalent” really means
It means one specific thing: at displacement speed, on a displacement hull, this motor produces about as much usable push as a 6 hp petrol outboard. It does not mean the boat will go as fast, and any page that implies otherwise is overselling.
Here is the basis for the estimate. A hull has a speed beyond which it will not go without climbing over its own bow wave — roughly 1.34 times the square root of the waterline length in feet, for a displacement hull. Below that speed, thrust is doing almost all the work of overcoming drag, so pounds of thrust are a fair comparison against a petrol engine’s push at the same speed. Above it, drag rises steeply and the petrol engine’s ability to keep turning a propeller at speed wins clearly. Even a 6 hp petrol outboard will plane a light boat. No electric motor of this class will.
So the useful reading of “6 hp equivalent” is: the same low-speed push, the same ability to hold a course in wind, the same reserve for getting off a lee shore — at displacement speeds, without the noise, the fuel and the servicing. If you want to plane, this is the wrong category of motor and we would rather tell you now.
Two more things the estimate is not. It is not a certification of any kind, and it is not a legal rating. Do not use it for insurance, registration, licensing or any official capacity calculation: those need the motor’s nameplate data, which is on the unit and in the specification table of each product page. The estimate exists to help you choose, nothing more.
Three sizing mistakes
1. Buying by watts. Watts tell you how much electricity the motor draws at full throttle — and the figures quoted are peak, not continuous. They do not tell you how much of that reaches the water as thrust, which depends on the propeller, the gearcase and the motor’s efficiency at low speed. Two motors with the same wattage can differ by 20 lb of thrust. Start from thrust, then check power and voltage.
2. Sizing for an empty boat. Almost everyone quotes the hull weight from the builder’s brochure, which excludes the outboard you are removing, the battery you are adding, crew, fuel, cooler and fishing gear. A 3.8 m aluminium boat that weighs 180 kg dry is routinely 600 kg on the water with two people aboard. Add up the real number before you choose, and if you are between two models, take the larger one.
3. Ignoring shaft length and voltage. A motor mounted too high will cavitate in chop and lose thrust exactly when you need it; the propeller has to sit below the hull line with the whole blade in clean water. Check your transom height before ordering, not after. The same applies to voltage: matching the motor to the battery you already own is a decision, not an afterthought.
FAQ
What thrust equals a 6 hp outboard? About 220 lb, which is the P400 at 3000 W on 48 V. On our working rule 500 W of peak input reads as one horsepower, so 3000 W is 6 hp.
How much thrust is a 3 hp outboard? About 130 lb, the P300 at 1800 W. A 3 hp petrol engine usually sits on a 3.5–4 m hull, which is the P300’s range.
What replaces a 5 hp petrol outboard? Between 150 and 220 lb. The P350 at 150 lb reads about 4 hp, the P400 at 220 lb about 6 hp. For a loaded 4–5 m boat we point at the P400.
What about a 4 hp? 150 lb, the P350 at 2100 W. This is the step where 48 V becomes worthwhile: the same power on 24 V would need a much heavier cable run.
What replaces an 8 hp? The P500. Nothing in the range sits between the P400 at 6 hp and the P500 at 12 hp, so an 8 hp boat moves up one step.
What replaces a 9.9 hp? The P400, even though it reads 6 hp. 9.9 hp is the default small outboard across Europe, and almost all of those boats are 4–5 m displacement hulls — exactly where 220 lb is enough.
What replaces a 15 hp? The P500 on a 48 V pack, where it runs 7500 W. On our rule 15 hp is about 7500 W, and 48 V feeds it without the cable weight of a 72 V setup.
Is there a 20 hp electric outboard motor? No. The P500 is the largest we make: 8000 W at 72 V, which we rate at 12 hp and 560 lb of thrust.
How long will the battery last? It depends entirely on battery capacity, and on how hard you use the throttle. The arithmetic is simple: amp-hours multiplied by voltage, divided by the motor’s wattage, gives you hours at full throttle. We do not quote runtime figures, because the same motor on two different batteries gives two completely different answers: a 100 Ah bank and a 50 Ah bank feeding the same motor differ by a factor of two before you touch the throttle. Size the battery around the day you actually plan.
Can I run a 24 V motor on a single 12 V battery? No. It will either not start or run badly, and you risk damaging the controller. Voltage has to match the motor’s rating; if you need more thrust than 12 V can deliver, the answer is two batteries in series, not one bigger battery.
Still not sure where your boat lands? Tell us the length, the loaded weight and what the boat is used for, and we will give you a thrust figure rather than a product name.
Tell us your boat length and weight — we’ll tell you the thrust you need