Description
What Pro XS Actually Changes
The 115 Pro XS is built on the same 2.1-liter inline-four as the standard Mercury 115 FourStroke. It has eight valves, a single overhead cam, and computer-controlled multi-port electronic fuel injection. If you are comparing spec sheets side by side, the blocks look nearly identical.
The difference is calibration and airflow. The Pro XS runs to 6,300 rpm against the standard 115’s 6,000, and it uses a top-mounted throttle body feeding a performance-tuned scroll intake manifold. Three hundred extra rpm sounds marginal, and at the top end it is: independent testing has put a Pro XS 115 at just over 37 knots at 6,300 rpm on a suitable hull, which is a modest gain over the standard engine.
Where it is not marginal is everywhere below that. The Pro XS delivers noticeably better hole shot and more mid-range torque. Mid-range response is what you actually experience in a bass boat that needs to get up and planing quickly from a launch, or in a bay boat navigating tight waters where you are constantly adjusting the throttle. Top speed is a number you quote at the ramp. Hole shot is what you feel every hour you run.
Mercury’s own framing for this engine is that displacing 2.1 liters lets it work less hard for the same output, which improves durability and service life alongside the performance. That is a fair description. A high-output engine that achieves its rating through displacement rather than boost or extreme rpm is a more relaxed engine at cruise.
Weight and Why It Is the Headline Spec
At 359 lb / 163 kg for the standard gearcase configuration, the 115 Pro XS is light for its output. The Command Thrust version runs 363 lb / 165 kg, a four-pound difference that is effectively nothing.
On a 17- to 18-foot aluminum or fiberglass bass boat, transom weight is a live design constraint. Every pound at the stern is a pound that affects how the hull sits, how it planes, and how it handles in chop. A lighter engine at the same horsepower is not a marketing point at this end of the market; it is a measurable performance advantage.
Command Thrust on the 115
The Command Thrust option runs a 2.38:1 gearcase against the standard 2.07:1, and it accepts larger propellers. The decision follows the same logic as the 40 to 60 HP range covered elsewhere in this catalog: standard gearcase for light, fast hulls and Command Thrust for heavier boats or where you struggle to plane.
At 115 HP the typical Command Thrust buyer is running a pontoon or a heavier bay boat. The typical standard gearcase buyer is running a bass boat and wants every knot. Neither is wrong, and both are available with 20-inch or 25-inch shafts.
Electrical and Rigging
The alternator produces 35 amps at 441 watts with a water-cooled voltage regulator. The water-cooled regulator matters and rarely gets mentioned: voltage regulators fail from heat, and a cooled one lasts considerably longer on an engine that runs hard.
Thirty-five amps supports the electronics load a serious fishing boat carries: a large sounder or side-imaging unit, a chart plotter, a live well pump, an aerator, deck lighting, and navigation lights, while charging the cranking battery.
Steering is available as dual cable mechanical or hydraulic power steering, and remote or tiller configurations exist. Controls are mechanical throttle and shift. The engine is SmartCraft compatible, so Mercury’s digital gauges give live fuel burn, engine hours, trim position, and diagnostic codes. Active Trim is available, which automatically adjusts trim through hole shots, turns, and changing water conditions rather than leaving you to manage it manually.
Fuel is unleaded regular, 87 octane minimum, or 90 RON, with up to 10 percent ethanol. Oil is NMMA certified FCW SAE 10W-30. Trim is power trim and tilt. Warranty is Mercury’s three-year limited plus a three-year corrosion warranty.
What It Suits
Aluminum and fiberglass bass boats from 17 to 18 feet, pontoons, flats boats, and bay boats in the same size range. It is the entry point into Mercury’s performance line and the most common choice for anglers who want Pro XS characteristics without stepping up to the weight and cost of a 150 or a V6.
Every Mercury 115 Pro XS we ship is new, factory sealed, and pre-delivery inspected before crating. Compare across the Fast Frenzy range and the Mercury outboard motors hub. Step down to the Potent Power range for 30 to 60 HP. For hull matching, see our rigid-hull inflatables and pontoon boats. Cross-brand, the closest in stock is the Yamaha F115 outboard motor.
Mercury Pro XS 115 HP: Full Factory Specifications
| Feature / Specification | Technical Detail / Value |
|---|---|
| Horsepower | 115 HP / 86 kW |
| Engine type | Inline-4, 8-valve single overhead cam (SOHC) |
| Displacement | 2.1 L / 126 CID |
| Full-throttle RPM range | 5300 to 6300 rpm |
| Air induction | Performance-tuned scroll intake manifold, top-mounted throttle body |
| Fuel induction | Computer-controlled multi-port electronic fuel injection (EFI) |
| Recommended fuel | Unleaded regular, 87 octane minimum or 90 RON, 10% ethanol max |
| Recommended oil | NMMA-certified FCW SAE 10W-30 |
| Ignition | SmartCraft digital inductive |
| Cooling system | Water-cooled with thermostat |
| Alternator | 35 amp / 441 W with a water-cooled voltage regulator |
| Starting | Electric (turn-key) with Smart Start |
| Controls | Mechanical throttle and shift |
| Steering | Dual cable mechanical or hydraulic power steering, remote or tiller |
| Gear shift | Forward, Neutral, Reverse |
| Gearcase ratio | 2.07:1 standard, 2.38:1 Command Thrust |
| Shaft lengths | 20 in / 508 mm, 25 in / 635 mm |
| Trim system | Power trim and tilt, active trim available |
| SmartCraft compatible | Yes. |
| Engine protection | SmartCraft Engine Guardian |
| Dry weight | 359 lb / 163 kg standard, 363 lb / 165 kg Command Thrust |
| CARB star rating | 3 stars |
| Color | Phantom Black |
| Warranty | 3-year limited, 3-year corrosion |
| Condition | New, factory sealed, PDI completed |
Frequently Asked Questions
Is the Mercury 115 Pro XS a V8?
No. The Mercury 115 Pro XS is an inline-four with 2.1 liters of displacement and an 8-valve single overhead cam. Mercury’s V8 Pro XS platform is the 4.6-liter, and it begins at 200 horsepower. The smallest V6 Pro XS is the 175. Any listing describing a 115 Pro XS as a V8 is incorrect.
What is the difference between the Mercury 115 FourStroke and the 115 Pro XS?
Both use the same 2.1-liter inline-four block. The Pro XS is calibrated to rev to 6,300 rpm against the standard engine’s 6,000 and carries a top-mounted throttle body feeding a performance-tuned intake. The top speed gain is modest. The meaningful differences are noticeably better hole shot and more mid-range torque, which is what you feel in normal running.
How fast is the Mercury Pro XS 115?
Independent testing has recorded just over 37 knots at 6,300 rpm on a suitable hull. Actual speed depends heavily on hull weight, load, and propeller selection. The Pro XS advantage over a standard 115 shows more in acceleration and mid-range pull than in outright top speed.
Should I order the Command Thrust gearcase on the 115 Pro XS?
Order Command Thrust if you run a pontoon or a heavier bay boat, since its 2.38:1 ratio and larger propeller capability plant a heavy hull on a plane more easily. Order the standard 2.07:1 gearcase for bass boats and lighter hulls where top speed matters. The weight difference between the two is four pounds, so weight is not a factor in the decision.
How much does the Mercury 115 Pro XS weigh?
359 lb (163 kg) in the lightest standard gearcase configuration, or 363 lb (165 kg) with Command Thrust. That is light for the output class, which matters on bass boats where transom weight directly affects how the hull planes and handles.
