In this guide
The most common pontoon mistake is undersizing the engine to save $2,000–$4,000 upfront. You'll feel it every single time you're on the water. Use the formula below to get your minimum HP, then buy at least the middle of your range — never at the bottom.
Why engine sizing matters more than most buyers realize
An underpowered pontoon doesn't just feel slow — it has real consequences. The engine runs at high throttle percentage just to maintain cruise speed, which accelerates wear, increases fuel consumption, and reduces the engine's service life. With a full load, an underpowered pontoon struggles to plane at all. In an emergency situation on a river with current, insufficient power can be genuinely dangerous.
The U.S. Coast Guard requires every boat to have a capacity plate stating the maximum HP rating — but there's no minimum. The minimum is the buyer's responsibility to get right.
HP by boat size — the reference table
| Boat length | Config | Min HP (calm lake) | Ideal HP (family) | Watersports HP |
|---|---|---|---|---|
| 18 ft | Twin tube | 50 | 75–90 | 90–115 |
| 20 ft | Twin tube | 60 | 90–115 | 115–150 |
| 22 ft | Twin tube | 90 | 115–150 | 150–175 |
| 24 ft | Twin tube | 115 | 150–175 | 175–200 |
| 22 ft | Tritoon | 115 | 150–175 | 175–225 |
| 24 ft | Tritoon | 150 | 175–200 | 200–250 |
| 26 ft | Tritoon | 175 | 200–250 | 250–300+ |
These ranges assume sea level altitude, typical 4–8 passenger load, and a standard boat weight for the listed configuration. Use our pontoon underpower calculator to get a personalized recommendation for your exact boat, weight, load, and altitude.
The four adjustments to make
1. Passenger load
The table above assumes a moderate load of 4–8 people. For boats that regularly carry near-maximum capacity, add 10–15% to the ideal HP figure. For solo or couple use, you can work with the minimum HP end of the range.
2. Use case
Watersports (tubing, skiing, wakeboarding) require significantly more HP than cruising because you need pull force, not just cruise speed. The watersports column in the table above reflects what you need for reliable, confident watersports performance — not the absolute minimum to drag a tube.
3. Water type
River use requires 10–15% more HP than calm lake use. Current means you need power reserve to maneuver safely, not just maintain cruising speed. On a river, HP is a safety margin as much as a performance factor.
4. Altitude
Engines lose approximately 3–5% of rated HP for every 1,000 feet above sea level due to thinner air. At 4,000 feet elevation, a 115 HP engine effectively produces around 93 HP. Adjust your HP target upward accordingly — add roughly 4% per 1,000 feet of elevation.
The most common mistake: buying at the minimum
Buyers frequently size to the minimum because the larger engine costs $2,000–$4,000 more. Over a 7-year ownership period, that's roughly $500/year. In exchange, you'll have confident performance under full load, better fuel economy at cruise, a longer engine service life, and the ability to tow tubes without apologizing for the boat every time.
It is almost always the wrong financial decision to undersize the engine. Once you own the boat, upgrading the engine is a $4,000–$8,000 project. Sizing correctly at purchase costs a fraction of that.
Sources & references
Frequently asked questions
How much horsepower do I need for a 22-foot pontoon?
For a 22-foot twin-tube pontoon used for family cruising with 4–7 people, 115 HP is the minimum for adequate performance and 150 HP is ideal. For watersports or river use on a 22-foot boat, 150–175 HP is appropriate. A 22-foot tritoon needs 150 HP minimum and performs best at 175–200 HP.
Is 90 HP enough for a 22-foot pontoon?
90 HP on a 22-foot twin tube is technically adequate for light loads on calm water, but it's underpowered for a family of 6 or any watersports use. You'll plane slowly with a full load and the engine will run near wide-open throttle to maintain cruise speed. For a 22-foot boat, 115 HP is the minimum we recommend for comfortable family use.
What is the maximum HP for a pontoon boat?
Maximum HP is printed on your boat's capacity plate — it's a legal limit, not a suggestion. Exceeding it voids your insurance and is illegal. Premium brands support 200–400+ HP on tritoon models. Entry-level 20-foot boats are often limited to 90–115 HP. Always check your capacity plate before purchasing a larger engine.
Does a bigger pontoon engine use more fuel?
A larger engine doesn't necessarily use more fuel at cruise speed — in fact, an adequately powered boat often uses less fuel than an underpowered one because it runs at lower throttle percentage to maintain speed. An underpowered pontoon running at 80–90% throttle to cruise at 20 MPH uses more fuel than a correctly powered boat cruising at 40–50% throttle.