Mercury Racing 360 APX Specifications
| Engine Model: Mercury Racing 360 APX |
| Engine Type: 4-stroke 8-cylinder DOHC 32-valve gasoline outboard engine |
| Total Displacement: 279 cu.in (4.6 L) |
| Rated Engine Power: 360 Hp (268 kW) at 7000 rpm |
| Fuel System: Electronic Fuel Injection (EFI) |
____________________________________________________________________________________
0The Mercury Racing 360 APX is a pure
competition outboard engineered exclusively to power Formula One tunnel
boats in the UIM F1H2O World Championship. Rated at 360 Hp from a
naturally aspirated 4.6-liter V8, this engine represents a revolutionary
step forward for circuit racing, delivering the durability and reduced
maintenance of a modern four-stroke while providing the power-to-weight
ratio essential for victory. Its defining characteristics include a
12-inch circuit-racing-specific midsection, an overdrive spur gearset
that enables 9600 RPM at the propshaft, and a lightweight carbon fiber
cowl that optimizes weight distribution.
The engine produces approximately 45 percent more torque than the
two-stroke racing outboards it replaces, and the sophisticated overdrive
system allows teams to trade some of this torque for increased propeller
speed, matching the performance characteristics of legacy engines while
enabling most teams to utilize existing propeller inventories. With 90
percent lower exhaust emissions than current two-stroke racing engines,
the 360 APX aligns with the sustainability initiatives of the UIM and
F1H2O organizations while setting a new benchmark for circuit-racing
performance.
Engine Type: 64-degree V8, Four-Stroke with Dual Overhead Cam (DOHC) and
32 valves
Power: 360 HP (268 kW) at the propshaft
Displacement: 4.6 Liters (279 cubic inches)
Bore and Stroke: 3.62 inches (92 mm) bore by 3.39 inches (86 mm) stroke
Compression Ratio: 11:1, increased from the base engine's 10:1
compression for competition performance
Full Throttle RPM: 7000 RPM
Idle RPM: 750 RPM
Induction System: Short-runner intake manifold with forced cold air
induction vented through the cowl
Fuel System: Electronic Fuel Injection (EFI) computer controlled with O2
and pressure feedback
Fuel Requirement: Unleaded Premium 91 Octane minimum (R+M/2) or 98 RON,
10% ethanol maximum
Ignition System: SmartCraft PCM 112 Digital Inductive with competition
calibration
Charging System: 85 amp (1071 watt) output for sustaining critical race
instrumentation and systems
Starting System: 24V electric start with SmartStart Protection for
instant dockside starting in competition
Throttle & Shift Controls: Digital throttle offering smooth and precise
application
Engine Management System: Competition spec SmartCraft PCM 112 with
specialized racing calibration
Engine Protection System: SmartCraft Engine Guardian with competition
calibration, monitoring critical sensors and adjusting power delivery to
prevent damage under extreme conditions
Exhaust System: Above water exhaust offering unrestricted flow and
producing an exciting tone for racing fans
Cooling System: Water-cooled with thermostat control and integrated
pressure relief
CARB Star Rating: 3-star, EU RCD II certified
Emissions Reduction: 90 percent lower emissions than current two-stroke
racing engines
Steering: Cable with wing plates, integrated lightweight steering arms
for tunnel boat cable steering
Steering Angle: +/- 30 deg for precise control in competition
The foundation of the 360 APX is its advanced 64-degree V8 powerhead,
derived from the Mercury Racing 300R 4.6-liter production engine but
extensively modified for the extreme demands of F1 tunnel boat racing.
The 64-degree cylinder angle provides inherent balance while maintaining
the compact profile essential for tunnel boat installations. The
cylinder heads incorporate dual overhead camshafts (DOHC) operating four
valves per cylinder, a 32-valve architecture that optimizes airflow and
combustion efficiency for maximum power output at elevated engine
speeds.
To prepare the engine for competition, Mercury Racing elevates the
compression ratio from the stock 10:1 to 11:1, increasing cylinder
pressures and thermal efficiency for greater power production. The
powerhead is naturally aspirated and features deep-breathing double
overhead cam architecture with a short-runner intake manifold mated to a
cold-air induction system vented through the cowl.
A cut-down flywheel and deleted balance shaft optimize weight and reduce
rotational inertia, enabling the engine to accelerate more rapidly under
the explosive demands of circuit racing. The top cowl and driveshaft
housing covers are constructed from lightweight carbon-fiber composite,
featuring robust quick-release latching and sealing systems that ease
access to the midsection.
The main element of the 360 APX is its competition-tuned Electronic Fuel
Injection system, managed by the SmartCraft PCM 112 engine control
module with specialized racing calibration. This advanced fuel delivery
architecture utilizes the 32-valve DOHC configuration and short-runner
intake manifold to optimize cylinder filling and combustion efficiency
across the 7000 RPM operating range.
The system incorporates O2 and pressure feedback, allowing the ECM to
continuously monitor and adjust fuel delivery for optimal performance
under the extreme acceleration and high-RPM conditions encountered on
the race course. The forced cold air induction system, vented through
the carbon fiber cowl, delivers dense, cool air directly to the intake,
maximizing volumetric efficiency and power output.
The fuel system is designed to operate on readily available 91-octane
pump gasoline with up to 10 percent ethanol content, reducing logistical
complexity for international race teams while maintaining competitive
power output.
The 360 APX employs a structural wet sump lubrication system with an
integrated baffle system and oil cooler, designed specifically for the
extreme lateral and longitudinal accelerations experienced in F1 tunnel
boat racing. The oil capacity is 6.6 liters (7.0 quarts). A dynamic oil
pickup system is designed to maintain critical engine oil pressure under
the high-G loads encountered during high-speed cornering and
acceleration.
Mercury Racing engineered a new high-performance full-synthetic
lubricant specifically for this engine: Mercury Racing High-Performance
Synthetic SAE 10W-30. This oil is formulated to withstand the extreme
heat and stress the engine encounters during F1 tunnel boat competition,
maintaining viscosity and protective properties under sustained
high-RPM, high-load operation.
The structural wet sump design integrates the oil reservoir within the
driveshaft housing, contributing to the engine's compact overall package
while ensuring reliable oil delivery under all racing conditions.
The cooling system on the 360 APX is a water-cooled design with
thermostat control and integrated pressure relief, engineered to
maintain consistent operating temperatures under the extreme thermal
loads of F1 competition. The system incorporates features to ensure
adequate cooling capacity during sustained high-RPM operation, including
integrated pressure relief to manage flow rates.
The above-water exhaust system not only provides unrestricted flow for
maximum performance but also produces an exciting tone appreciated by
racing fans. The exhaust exits above the water surface, reducing back
pressure and enhancing power output while contributing to the
distinctive sound of F1 tunnel boat racing.
| Mid Section and Lower Unit |
The mid section of the 360 APX is a 12-inch, circuit-racing-specific
assembly designed specifically for Formula 1 tunnel boat applications.
This robust housing incorporates a structural wet sump driveshaft
housing with integrated power trim and lift operated by remote pumps.
The lift range is 26 mm (1 inch), allowing precise vertical adjustment
of engine height for optimal performance on different race courses.
The midsection is designed to accommodate the extreme loads of F1 tunnel
boat racing while providing the adjustability required for fine-tuning
race setup. The driveshaft housing covers feature quick-release
fasteners to ease access to the midsection for maintenance and setup
adjustments.
The lower unit features an evolved Mercury Racing Super Speed Master (IV
SSM) outboard gearcase, a direct-drive unit with no neutral or reverse
shifting, reflecting its pure competition purpose. This gearcase is
engineered for minimum drag and maximum strength at the extreme speeds
achieved in F1 competition.
An overdrive spur gearset between the crankshaft and the gearcase
increases the input shaft speed to the gearcase to match that of the
current 9600 RPM two-stroke race engine and produces the left-hand
propeller rotation desired for Formula 1 circuit racing. The overdrive
gears are designed to accommodate multiple gear ratios, allowing teams
to select the ratio that best fits each particular race course. The
available overdrive ratios are 0.714 (35:25) and 0.739 (23:17), with
corresponding overall drive ratios of 0.809 and 0.837.
Midsection Length: 12 inches (305 mm), circuit racing specific
Gearcase: Mercury Racing Super Speed Master (IV SSM), direct-drive, no
neutral or reverse
Gear Ratio: 1.13:1 (15:17)
Overdrive Ratio: 0.714 (35:25) / 0.739 (23:17)
Overall Drive Ratio: 0.809 / 0.837
Lift Range: 26 mm (1 inch)
Propeller Rotation: Left-hand
The 360 APX incorporates a race-specific power trim and lift system with
remote pumps. The maximum trim range is 13 deg, providing the adjustment
range necessary for optimizing boat attitude and performance under
varying race conditions. Unlike recreational outboards, the 360 APX has
no tilt range specification, as the system is designed specifically for
competition setup rather than trailering or shallow-water operation.
The trim and lift system is integrated into the structural 12-inch
midsection, providing the adjustability required for fine-tuning race
boat setup while maintaining the rigidity essential for high-speed
stability. Remote pumps operate the hydraulic system, allowing precise
control of engine height and trim angle during race setup.
Propeller selection for the 360 APX is a critical performance
consideration, and Mercury Racing engineered the powertrain specifically
to accommodate the unique requirements of F1 tunnel boat racing. The 360
APX produces approximately 45 percent more torque than the two-stroke
racing outboard it replaces, but at a lower engine speed.
The primary purpose of the overdrive spur gearset is to increase the
input speed to the gearcase, matching the 9600 RPM propeller speeds of
the two-stroke engines previously used in F1H2O competition. This
engineering approach allows teams to trade some torque for increased
propeller RPM, which also improves the life span of the gears. The
overdrive system is designed to accommodate multiple gear ratios (0.714
and 0.739), enabling teams to select the ratio that best fits each
particular race course and conditions.
The IV SSM gearcase is designed for left-hand propeller rotation,
matching the requirements of F1 tunnel boat racing applications.
Specific propeller pitch and diameter recommendations depend on boat
setup, race course conditions, and team preferences, with the overdrive
system and multiple gear ratio options providing the flexibility to
optimize performance across a range of propeller choices.
Dry Weight: 430 lbs (195 kg)
Shaft Length: 12 inches (305 mm) circuit-racing-specific midsection
Overall Dimensions: Compact V8 packaging optimized for F1 tunnel boat
installations
Engine Oil: Mercury Racing High-Performance Synthetic SAE 10W-30,
specifically formulated for this engine. Oil Capacity: 6.6 liters (7.0
quarts). Lubrication System: Structural wet sump with integrated baffle
system and oil cooler requiring regular inspection.
Cooling System: Water-cooled with thermostat control and integrated
pressure relief requiring regular inspection and maintenance. Fuel
System: Designed for 91-octane pump fuel, simplifying logistics compared
to specialized racing fuels.
Engine Guardian System: SmartCraft Engine Guardian with Competition
Calibration monitors sensors and can reduce power to protect the engine
if faults are detected. Warning System: SmartCraft digital
instrumentation provides comprehensive engine data and fault
notification.
Access: The carbon fiber cowl features robust quick-release latching,
and the driveshaft cover has quick-release fasteners to ease access to
the midsection for maintenance. Break-In Requirements: Specific break-in
procedures must be followed for new engines before full-throttle
competition operation.
The Mercury Racing 360 APX is designed for a singular, highly specific
application: UIM F1H2O World Championship tunnel boat racing. These are
carbon fiber tunnel-hull catamarans weighing approximately 510 kg (1,124
lbs) including the engine and driver. The series attracts up to 20 of
the world's leading drivers competing in tunnel-hull catamarans that
hairpin turn at more than 90 mph (145 km/h) and top 140 mph (225 km/h)
on the straights. The boats measure approximately 16 feet (4.8 meters)
in length and are capable of hairpin turns at extreme speeds, with up to
20 boats competing simultaneously on race courses, navigating spray and
wakes in high-speed competition.
____________________________________________________________________________________
| Outboard Engines Technical Specifications |
| Small Engines Technical Specifications |
| Car Engines Technical Specifications |
| Industrial Engines Technical Specifications |
