Mercury Pro XS 250 HP 4-Stroke Outboard Engine | 4.6L V8 DOHC, 20″ or 25″ Shaft

Description

Where the 250 Sits

Two hundred and fifty horsepower is one of the most common hull ratings in the recreational market, particularly for offshore center consoles and larger bay boats in the 22- to 26-foot range. If your capacity plate reads 250, this engine is the ceiling, and the reason to buy it is straightforward.

If your hull is rated higher, look at the 300 before deciding. On our current pricing, the two are separated by $1,000 for 50 horsepower on the same block, at the same weight, with the same rigging. That is not a close call, and we would rather say so than sell you the wrong engine.

The 4.6-litre V8 at 250 HP

The block is the same 4.6-liter, 64-degree V8 used from the Pro XS 200 upward: 92 x 86 mm bore and stroke, dual overhead cams, 32 valves, 279 cubic inches. At 250 horsepower it is running at roughly 83 percent of what Mercury asks of it in the 300, which is still comfortably inside its design envelope.

Four valves per cylinder and twin cams allow independent intake and exhaust timing, which is what gives this engine its breadth. It pulls hard from low rpm because of displacement, and it keeps breathing at the top because of valve area. The result is a torque curve that stays useful across the whole 5,600 to 6,200 rpm band rather than peaking in a narrow window.

The exhaust is performance-tuned rather than simply silenced. Mercury shapes the note deliberately on the V8 Pro XS range, which is a detail the buyer at this level notices and values.

Electrical Capacity on a Fully Rigged Boat

A 250 HP boat is typically the most heavily rigged vessel in a private owner’s fleet: twin large-format displays, radar on some hulls, VHF, autopilot, live wells, wash-down pumps, deck lighting, stereo, and a trolling motor charging bank.

The alternator delivers 85 amps and 1,071 watts at wide open throttle and 20 amps at idle, with idle charge automatically raising idle rpm to lift output when a battery runs low. That last feature is the one that saves days. Extended trolling or drifting with the full electronics load running draws more than 20 amps, and without idle charge, you return to a cranking battery that won’t turn the engine over.

The Rest of the V8 Feature Set

Adaptive speed control holds a target rpm regardless of load and sea state, without throttle input. Transient Spark adds ignition timing advance during throttle transitions for extra torque on acceleration. Advanced range optimization with closed-loop fuel control leans the mixture at cruise, which on an offshore run at part throttle is where the fuel bill is actually decided.

Ignition is SmartCraft PCM 112 digital inductive. Starting is electric with SmartStart protection. Steering is hydraulic as standard, power is optional, and the big tiller is optional. Shaft lengths are 20 inches and 25 inches. The trim range is 20 degrees and the tilt range is 73 degrees.

The TorqueMaster gearcase runs 1.75:1 with a 1.25-inch propeller shaft built for semi-surfacing high-speed operation, where the prop runs partly clear of the water and loads intermittently.

Fuel is unleaded regular at 87 octane minimum or 90 RON, up to 10 percent ethanol. The warranty is three years limited plus three years of corrosion.

What It Suits

Offshore center consoles from 22 to 26 feet, larger bay boats, tournament hulls, performance runabouts, and pontoons at the top of their rating. Also a common single-engine repower for boats previously carrying a 250 HP two-stroke.

Every Mercury 250 Pro XS we ship is new, factory sealed, and pre-delivery inspected before crating. Compare across the Pro XS 200 to 300 range, the Verado 250 to 600 range, and the Mercury outboard motors hub. For hull rating and rigging advice, send us your boat details.

Mercury Pro XS 250 HP: Full Factory Specifications

Frequently Asked Questions

Should I buy the Mercury 250 Pro XS or the 300 Pro XS?

Buy the 250 if your hull capacity plate is rated at 250 HP maximum, because exceeding a hull rating typically voids insurance and can be illegal. If your hull permits 300, the 300 Pro XS uses the same 4.6-liter V8 block and weighs the same 505 lb with the same rigging, so there is no weight, size, or installation penalty for taking the larger engine.

Is the Mercury 250 Pro XS the same engine as the 200 and 225?

Yes, mechanically. All V8 Pro XS models from 200 to 300 share the 4.6-liter block, the 92 x 86 mm bore and stroke, the 32-valve DOHC powerhead, the 85 amp alternator, and the 505 to 511 lb dry weight. Mercury differentiates them by calibration. The installation is identical across all four.

What electrical output does the Mercury 250 Pro XS provide?

85 amps at 1,071 watts at wide open throttle, and 20 amps at idle. Idle Charge technology automatically raises idle rpm to increase alternator output when it detects a low battery. That matters on a fully rigged boat, where extended trolling with displays, pumps, and running lighting draws more than 20 amps and would otherwise flatten the cranking battery.

Does the Mercury 250 Pro XS need premium fuel?

No. It runs on unleaded regular at 87 octane minimum (R+M/2) or 90 RON, with up to 10 percent ethanol. Advanced range optimization with closed-loop fuel control manages the mixture automatically and provides tolerance for variable fuel quality, which matters when refueling at unfamiliar marinas.

How heavy is the Mercury 250 Pro XS?

505 to 511 lb (229 to 232 kg) depending on configuration. Your transom capacity plate lists a maximum weight as well as a maximum horsepower, and both need checking before you order. The weight is identical across the whole V8 Pro XS range, so stepping up or down in horsepower does not change your transom loading.