The right outboard size starts with your boat’s capacity plate: it states the maximum horsepower the hull is rated for, and you should never exceed it. Within that limit, choose based on the boat’s length and weight, the load you carry and how fast you want to go. A small jon boat may only need a few horsepower, while a loaded 16-foot boat usually benefits from a motor near its rated maximum.
Start with the capacity plate
US-built boats carry a capacity plate near the helm or transom listing maximum horsepower, persons and load. Exceeding the horsepower rating is unsafe and can affect insurance and legality. If the plate is missing, the manufacturer can usually provide the rating.
Typical sizes by boat length
| Boat | Typical outboard range | Notes |
|---|---|---|
| Inflatable or tender | 2.5 to 9.9 HP | See outboards for inflatable boats |
| 12 ft aluminum jon or V-hull | About 6 to 15 HP | Check the plate; many are rated around 10 to 15 HP |
| 14 ft aluminum boat | About 9.9 to 25 HP | A 15 to 20 HP planes most loads |
| 16 ft aluminum boat | About 25 to 50 HP or more | Varies widely with hull width and rating |
| 18 ft boat | Often 60 HP and up | Usually beyond portable motors |
These ranges are only typical; your boat’s plate is the limit.
Factors that change the answer
- Load: passengers, gear and fuel add up; a motor that barely planes an empty boat will struggle loaded.
- Use: trolling and calm lakes need less power than open water or current.
- Weight: portable motors up to about 9.9 to 15 HP can be carried; larger motors usually stay mounted.
- Shaft length: match the transom height; see the outboard shaft length guide.
- Controls: tiller or remote steering, pull or electric start; see electric start vs pull start.
Is 9.9 HP enough?
For many 12 and 14 foot aluminum boats, a 9.9 HP moves the boat well, and in some areas it is a popular size because of local horsepower limits on certain waters. With heavier loads, a 15 to 20 HP planes more easily if the plate allows it.
Outboards we carry
Our range covers 2.5 to 30 HP Mercury, Suzuki and Tohatsu four-strokes, such as the Mercury 15 HP 15MLH EFI at $3,155.00 and the Suzuki 20 HP DF20ATS5 at $3,490.00. Compare every size on our outboard motors by horsepower page, and see outboards for jon boats and the boat speed calculator.
More guides: boat won’t get on plane · how many hours is a lot for an outboard · Tohatsu vs Mercury · Suzuki vs Mercury · 9.9 vs 15 HP · 20 vs 25 HP · tiller vs remote · outboard motor prices by HP · outboards for sailboats · outboards for canoes.
Shipping is a flat $80.00 per order to US addresses, with 15-day free returns. Questions? Ask a parts specialist.