The difference between a 9.9 HP and a 15 HP outboard is often smaller than the numbers suggest. On many brands, the 9.9 and 15 share the same basic engine and weigh about the same, with the 15 set up to produce more output. The 9.9 exists largely because many lakes and waterways limit horsepower to under 10 HP, and some areas set registration or licensing thresholds near that size. If your water has a limit, the 9.9 is the answer; if not, the 15 gives more speed and load capacity for a modest price difference.
9.9 vs 15 HP at a glance
| 9.9 HP | 15 HP | |
|---|---|---|
| Main reason to choose | Waters with a horsepower limit, kicker use | More speed and load on unrestricted water |
| Weight | Often similar to the 15 of the same brand | Often similar to the 9.9 |
| Fuel use | Slightly lower | Slightly higher at full throttle |
| Starting price in our range | Tohatsu $2,600.00, Suzuki $2,655.00, Mercury $2,865.00 | Tohatsu $2,890.00, Suzuki $2,895.00, Mercury $3,130.00 |
Check the weight and shaft length of the specific models in each listing.
Horsepower limits
Many lakes, reservoirs and some states limit motors to under 10 HP, which is why 9.9 HP models are so common. Check local rules before buying a 15. Some owners ask about converting a 9.9 to 15; whether that is possible depends on the model, and it can break local limits and registration rules, so treat it as a question for the manufacturer and your local authority.
How fast will each go?
Speed depends far more on the boat’s weight and hull than on the motor’s badge. On a light jon boat or small aluminum boat with one or two people, the extra power of a 15 is noticeable; on a heavy boat or pontoon, neither will plane. Estimate with our boat speed calculator, and see boat won’t get on plane.
Mercury 9.9 vs 15
Many of the Mercury 9.9 and 15 HP models we list are EFI four-strokes, as their names show; compare tiller, starting and shaft options in the listings on 9.9 HP outboards and 15 HP outboards.
Buying used
Because 9.9 and 15 HP motors often look identical, check the model code and decal on a used motor, and ask for hours and service records; see how many hours is a lot for an outboard.
Kicker motors
As a kicker on a larger boat, a 9.9 is the usual choice for trolling and backup power; see kicker motors.
See also what size outboard do I need? and 20 vs 25 HP.
More guides: Mercury outboard model codes · 9.9 hp outboards compared · Tohatsu 9.8 vs 9.9 · outboard motor prices by HP.
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