What Size Outboard Motor Is Right for Your Boat?

Choosing the right horsepower (HP) motor for your boat isn’t just about speed—it’s also about safety, performance, efficiency, and handling. Whether you’re running a dinghy, inflatable, trailer boat or sailboat, matching the motor to your craft’s size, weight, and intended use makes all the difference. This guide breaks down the best motor size ranges and what you can expect from each, to help you make a confident choice.

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Motor HP & Boat Length: A Quick Overview

Motor HP Range	Boat Length (feet)	Boat Length (metres)
2 – 10hp	8′ – 12′	Up to ~3.5 m
5 – 15hp	8′ – 14′	Up to ~4.2 m
9 – 20hp	11′ – 16′	Up to ~4.5 m
20 – 40hp	13′ – 18′	Up to ~5.0 m
40 – 75hp	14′ – 20′	Up to ~5.5 m
90 – 140hp	16′ – 25′	~6.0 m +

HP Ranges & What to Expect

2 – 3.6hp (Very Light / Portable Motors)

Great for canoes, small folding or inflatable boats, dinghies, and other very lightweight watercraft. These motors tend to be simple in design, easy to carry, often with forward or forward-neutral gears only. Expect speeds around 8-16 km/h depending on your hull.

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5 – 6hp

For slightly larger inflatables, small dinghies, folding boats, and those needing a portable option with more control. Hulls weighing between ~22-113 kg and around 2.5-3.5 m long fit well here. Some of these motors also come with forward-neutral-reverse gearsets and longer shafts (20") for sailboat or auxiliary use.

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8 – 9.8hp

These outboards offer more power for larger inflatables or aluminium/fibreglass boats around 3-4.5 m in length. Two-cylinder designs provide smoother performance, reduced vibration, and better handling under moderate loads.

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15 – 25hp

This range is where you begin to see fuller-featured outboards, suitable for more demanding applications. Ideal for larger fishing or recreational boats in the 3.5-5 m range, heavier loads, multiple passengers, or where speed and planing become important.

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Key Factors to Consider

• Hull Type & Weight: A heavier hull needs more power to handle well, especially in rough conditions.

• Shaft Length: Short shaft (usually ~15") is common, but if your boat design needs it (e.g. transom height or sailboat applications), you may need a longer shaft.

• Load & Passengers: How many people, gear, and how often will you be fully loaded? That “real-life” weight can significantly affect performance.

• Fuel Efficiency & Features: Higher HP motors often feature better controls, fuel tanks, electric start, etc.—but they also consume more fuel.

• Use-Case: Is this your primary motor, kicker/auxiliary, for trolling, or occasional use? Each case may shift what’s optimal.

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Final Tip: Talk to Your Local Dealer

If you’re unsure or between sizes, visiting your local Parsun dealer is a great move. They can help you assess boat weight, hull shape, typical use, and recommend the best fit so you get reliable performance—not just raw power.