What Size Outboard for My Boat? Easy HP Chart + Best Motors From $885 (2026)

What size outboard for my boat? We hear that question more than any other at our shop in Fresno, California, and the answer is easier than most people think. You need four things: your boat’s capacity plate, its weight, how you’ll use it, and your transom height. Get those right and the motor almost picks itself.

We sell outboards from 2.5 HP to 425 HP, from Yamaha, Mercury, Suzuki, Honda, Tohatsu and Evinrude, and we ship them worldwide. So below you’ll find a simple sizing method, a horsepower chart by boat type, the specs that matter, and real motors with our prices. If you’ve been asking yourself what size outboard for my boat, this page should settle it.

What Size Outboard for My Boat: The 4 Step Method

1. Read the capacity plate. It tells you the most horsepower your boat can legally and safely carry.
2. Work out the total weight: boat, motor, fuel, people and gear.
3. Decide how you’ll use it: displacement speed, planing, towing, or trolling.
4. Measure your transom so you get the right shaft length.

Let’s go through each one, because each step changes what size outboard for my boat really means for you.

Step 1: Check the Capacity Plate

Most powerboats under about 20 feet have a capacity plate near the helm or on the transom. It shows the maximum horsepower, the maximum number of people and the maximum weight. In the US it’s required by the Coast Guard, and you can read more on the US Coast Guard boating safety site. Many other countries have their own version.

The plate is the first answer to what size outboard for my boat. Never go over the maximum horsepower on the plate. It’s there because the hull, the transom and the steering were designed for that much power and no more. Going over can make the boat dangerous, and in many places it can void your insurance.

No plate? That’s common on older boats, sailboats, inflatables and boats over 20 feet. In that case, ask the builder, look for the original brochure, or use the weight method in step 2.

Step 2: Work Out the Total Weight

Horsepower moves weight, so weight is the second answer to what size outboard for my boat. A good rough guide for planing boats is:

• About 1 HP for every 25 to 40 lb (11 to 18 kg) of total weight for a boat that planes easily and quickly.
• About 1 HP for every 40 to 60 lb (18 to 27 kg) if you’re fine with slower planing and moderate top speed.

Total weight means everything: the hull, the motor, full fuel, batteries, people, coolers and gear. People always forget the gear. So when someone asks us what size outboard for my boat, our first question is usually how many people and how much stuff.

Example: a 16 foot aluminum boat weighs about 400 lb. Add a 50 HP motor at about 220 lb, fuel at 80 lb, two people at 400 lb and gear at 100 lb. That’s about 1,200 lb. At 1 HP per 25 to 40 lb, you’d want 30 to 50 HP, and the plate on most 16 footers allows 40 to 60. So a 40 or 50 HP is the sweet spot.

Step 3: How Will You Use It?

Displacement speed (not planing)

Sailboats, heavy dinghies, canoes and some workboats don’t plane. They’re limited by hull length, so more power past a point just burns fuel. Small motors from 2.5 to 9.9 HP are normal here, often with high thrust props.

Planing

Most powerboats are made to get up on plane. You need enough horsepower to push over the hump quickly with a full load. This is where people most often buy too small.

Towing skiers and tubes

If towing is the reason you’re asking what size outboard for my boat, go toward the top of your plate rating. Pulling a skier out of the water takes a lot more power than cruising.

Trolling

If you troll a lot, you may want a main motor plus a small kicker. See our guide on the best 9.9 HP outboard picks for kickers.

Step 4: Measure the Transom for Shaft Length

Horsepower is only half of what size outboard for my boat means. The other half is shaft length. Measure from the top of the transom, where the motor clamps on, straight down to the bottom of the hull.

Too short and the prop sucks air and cavitates. Too long and the gearcase drags, slowing you down and throwing spray. Our long shaft outboard guide goes into this in more detail.

What Size Outboard for My Boat? Quick Chart by Boat Type

These are typical ranges. Your capacity plate always wins over this chart. If you’re still unsure what size outboard for my boat means for your exact hull, send us the make, model and length and we’ll tell you what we’d fit.

Sizing by Boat Type, in More Detail

Inflatables and tenders

Weight is everything here, because you’ll lift the motor on and off. For an 8 to 10 foot dinghy, a 2.5 to 6 HP four stroke is plenty to putter to shore. If you want a 10 to 12 foot RIB to plane with two people, you’ll need 15 to 20 HP, and most RIBs that size are rated for it. Our Mercury 15 HP range is light and fuel injected.

Jon boats and small aluminum boats

A 12 foot jon boat on a quiet lake is happy with 6 to 9.9 HP. A 14 footer that you want to plane with two people and gear does better with 20 to 25 HP. Many lakes cap you under 10 HP, so check your local rules before you decide what size outboard for my boat makes sense. A Mercury 9.9MH at $1,272 or a Suzuki DF9.9BS5 at $2,640 are both good fits.

16 to 18 foot fishing boats

This is the size where people most often under power. A 16 foot deep V with three people and a full livewell needs 50 to 60 HP to plane well. At 17 to 18 feet you’re looking at 90 to 115 HP. Check our Yamaha 60 HP and Yamaha 90 HP listings, or the Suzuki 115 HP range.

Pontoons

Pontoon owners ask what size outboard for my boat more than anyone. Pontoons are heavy and push a lot of water. A small 18 foot pontoon cruising with a few people can get by on 40 to 60 HP. If you want to pull tubes, or you have a 22 foot and up tritoon, go 115 HP or more. Motors with big gearcases and low gearing, like Mercury’s Command Thrust or Yamaha’s high thrust models, swing bigger props and suit pontoons well.

Bass, bay and center console boats

These are usually rated high, and most owners run close to the max. For a bay boat or center console of 20 to 24 feet, 150 to 300 HP is normal. See our Suzuki 200 HP buying guide, our Mercury 250 HP buying guide and the Yamaha V MAX SHO range.

Sailboats

A sailboat motor only needs to push the hull to hull speed. For 20 to 30 foot sailboats, 4 to 9.9 HP is normal. Pick a long or extra long shaft so the prop stays in the water when the stern lifts in waves, and pick a high thrust prop if you can. Electric is also worth a look: our Torqeedo Cruise guide covers that.

Big boats and repowers

Over 25 feet, twin engines are common. For offshore, two motors also give you a way home if one fails. The Yamaha 425 HP and Mercury Pro XS are popular for these.

Specs of Popular Sizes We Sell

Weights are approximate and depend on shaft length and options. Each listing has the details.

Too Small vs Too Big

When people ask what size outboard for my boat, they usually worry about going too big. In our experience, going too small is the more common mistake.

Too small

• The boat struggles to plane, or won’t plane at all with a full load.
• The motor runs near full throttle all the time, which wears it faster.
• Fuel use is often worse, because a small motor working hard is less efficient than a bigger one loafing.
• You have no reserve power for bad weather or a strong current.

Too big

• It can be unsafe and illegal if it’s over the plate rating.
• The extra weight sinks the stern and can let water in over a low transom.
• It costs more to buy and more to insure.

Our advice: aim for 75 to 100 percent of your plate rating for most planing boats. That’s the honest answer to what size outboard for my boat for most people.

Real Examples From Our Customers

Numbers on a chart are fine, but it helps to see how it plays out. Here are a few real situations that came through our shop, with names left out.

The overloaded 16 footer

A buyer had a 16 foot aluminum boat rated for 50 HP and was running a 25. With himself, his brother, two kids and a cooler, the boat would barely plane. He asked us what size outboard for my boat would fix it without breaking the bank. We put him on a 40 HP with electric start and power tilt. He told us later it planes in a few seconds now, and because the motor isn’t screaming at full throttle, his fuel use went down.

The sailboat that only needed 6 HP

Another customer with a 26 foot sailboat wanted a 15 HP because he figured more is better. The boat’s hull speed is about 6.5 knots, and a 6 HP high thrust motor will get it there in calm water. We talked him into a long shaft 6 HP Sail Pro. He saved money and about 20 kg on the stern, which made the boat sit better and the motor easier to lift.

The pontoon that couldn’t pull a tube

A family with a 22 foot pontoon had a 50 HP from the original owner. It was fine for cruising but useless for tubing. When they asked us what size outboard for my boat for towing, the plate allowed 115, so we suggested a 90 to 115 with a big gearcase. That’s the range where pontoons start to feel lively.

The inflatable that was too heavy to carry

A boater bought a 20 HP for his 10 foot inflatable tender because it was rated for it. Then he had to lift it onto a yacht’s swim platform every trip. We swapped him to a light 9.9. Sometimes what size outboard for my boat isn’t about speed at all. It’s about what you can carry.

How Much Faster Will More Horsepower Make It?

Speed doesn’t go up in a straight line with horsepower. As a rough guide, doubling the horsepower on a planing boat often adds something like 30 to 40 percent to top speed, not double. That’s because drag climbs fast as speed goes up. So going from a 40 to a 60 on a 16 footer might add a few mph at the top, but the real gain is how quickly it planes with a load, and how relaxed the motor feels at cruise.

If top speed matters most to you, look at weight as well as power. A lighter motor of the same horsepower can make a small boat noticeably faster.

Heavy Loads, Work Boats and Hot Climates

If you carry heavy loads, run in strong currents, or use the boat for work, size up. Commercial fishermen and ferry operators often run close to the max rating, and they pick motors with high thrust gearing so they can swing bigger props. Hot weather and high altitude also take power away from any engine. A lake high in the mountains can cost you a noticeable chunk of power, so if that’s your water, factor it in when you work out what size outboard for my boat.

Common Mistakes When Sizing an Outboard

• Forgetting the load. The boat might plane with one person and nothing else. Load it the way you really use it.
• Wrong shaft length. This is the most common ordering mistake we see. Measure first.
• Ignoring weight on the transom. A heavy four stroke on a small, light boat can make it sit stern down.
• Buying for top speed only. Most of your time is at cruise. Buy for that.
• Not checking local rules. Some lakes cap horsepower, and some ban gas motors outright.
• Forgetting controls. A remote motor on a boat with no steering needs cables, a helm and a control box.

Checklist Before You Order

Before you buy, run through this list. It’s the short version of what size outboard for my boat in practice:

• Capacity plate maximum HP written down
• Total weight worked out, including people and gear
• Use decided: displacement, planing, towing or trolling
• Transom height measured for shaft length
• Tiller or remote decided
• Pull or electric start decided
• Manual or power tilt decided
• Local rules checked for HP limits

Got all that? Then you know what size outboard for my boat looks like for you, and you can pick a brand and model with confidence.

Tiller or Remote Steering?

Up to about 30 HP, tiller steering is simple and cheap. From 40 to 60 HP you can get either, and tiller is popular on fishing boats. Above about 90 HP almost everything is remote, with a steering wheel, cables and a control box. Remember that a remote motor needs those parts, and they add cost if your boat doesn’t have them. Our tiller outboard and electric start outboard pages show the options.

Single or Twin Engines?

For most boats under 24 feet, one motor is simpler and cheaper. Twins make sense on bigger offshore boats for safety and for handling. If you’re thinking twin, work out what size outboard for my boat in total horsepower, then split it. Two 150s on a boat rated for 300 HP, for example.

Two Stroke or Four Stroke Changes the Weight

Older boats were often rated with two strokes in mind, and two strokes are lighter for the same power. A modern four stroke of the same horsepower can be noticeably heavier, especially from 40 HP up. If your boat is small, light or has a low transom, that extra weight matters. It can push the stern down, slow the planing, and cut your freeboard at the back.

So when an older boat owner asks us what size outboard for my boat, we look at the weight the boat was designed for, not just the horsepower. Sometimes the right answer is the same horsepower in a lighter model, or one size down. Direct injection two strokes like the Evinrude E-TEC sit in the middle, lighter than most four strokes. See our Evinrude E-TEC outboards if weight is a worry.

One more thing on weight: fuel. A full 25 litre tank weighs close to 20 kg. Put it in the right spot in the boat and you’ll get better trim and speed. That’s a small detail, but it’s part of answering what size outboard for my boat for real life, not just on paper.

Don’t Forget the Prop

Even when you’ve solved what size outboard for my boat, the prop can let you down. The right motor with the wrong prop still runs badly. When your boat is loaded the way you normally use it, the motor should reach the top of its recommended RPM range at full throttle. If it doesn’t, you need less pitch. If it goes past it, you need more. Getting the prop right can make a 60 HP feel like a 70.

How to Order the Right Motor From Us

1. Send us your boat’s make, length and capacity plate rating if you have it.
2. Tell us how you’ll use it and your transom height.
3. We’ll suggest a size and shaft length, with real prices.
4. Order on the product page, or call or WhatsApp +1 209 690 5983.
5. Your motor ships in its crate, with tracking, to your country.

New to buying online? Read our guide on how to buy outboard motor online, see the outboard motor with free shipping page, or check our cheap outboard motors if budget matters most. More general boating advice is on Discover Boating.

What Size Outboard for My Boat: FAQ

How do I know what size outboard for my boat without a capacity plate?

Use the weight method: about 1 HP for every 25 to 40 lb of total weight for good planing. Then ask the builder or check the original brochure.

Can I put a bigger motor than the plate allows?

We don’t recommend it. It can be unsafe, illegal and can void insurance.

What size outboard for my boat if it’s a 14 foot aluminum?

Usually 15 to 25 HP. Check the plate, as some 14 footers allow more.

What size outboard for my boat if it’s a pontoon?

40 to 60 HP for a small pontoon cruising. 90 HP or more for bigger ones or for towing.

Does a bigger outboard use more fuel?

Not always. A motor that’s a bit bigger and running at part throttle can use less fuel than a small one at full throttle.

Do you ship worldwide?

Yes. We confirm the cost and timing for your country before you pay.

Final Word

So, what size outboard for my boat? Read the plate, add up the weight, think about how you’ll use it, and measure the transom. For most planing boats, aim for 75 to 100 percent of the plate rating. If you’d like us to do the math, call or WhatsApp +1 209 690 5983 or use our contact page. You can browse every brand in our shop, read our customer reviews, or learn more about us.