By: Scott Way
An Apex Series Four-Stroke V8 Designed for Formula 1 Tunnel Boat Competition
Mercury Racing has revealed an all-new 360 APX competition outboard for 2021 that will be available to race teams for closed course competition, namely the upcoming UIM F1H2O World Championship. The engine is a potent four-stroke V8 designed specifically to power Formula One tunnel boats, and will be the first model in a new Mercury Racing Apex Series of outboards designed for closed-course competition. The new engine is expected to be available by November 2020 to qualified race teams.
According to Stuart Halley, Mercury Racing's general manager, “The 360 APX will usher in a new era of performance for this premier class of tunnel boat racing. It combines a durable, low-emissions, four-stroke powerhead with amazing performance, and will require much less maintenance than the two-stroke outboard currently in use in the F1H2O World Championship.”
The UIM F1H2O World Championship is the flagship international series of single-seater inshore circuit powerboat racing. The series attracts up to 20 of the world's leading drivers competing in tunnel-hull catamarans that take hairpin turns at more than 90 mph and top 140 mph on the straights. In 2019, nine teams and 18 drivers from 12 countries competed in the six-race World Championship, with American pilot Shaun Torrente, racing for Team Abu Dhabi, winning the title. The 2020 UIM F1H2O World Championship schedule has been postponed due to the COVID-19 pandemic.
The 360 APX is based on a modified version of the current Mercury Racing 300R 4.6-liter V8 powerhead. The engine is normally aspirated and retains its double overhead cam/four-valve architecture. The compression ratio is increased from 10:1 to 11:1 and peak rpm is boosted from 6400 RPM to 7000 RPM. The powerhead is fitted with a short-runner intake manifold mated to a cold-air induction system vented through the cowl. The engine calibration is modified to take full advantage of the powerhead modifications. The 360 APX uses a 24-volt starter for faster dock-side starting in competition. A digital control offers smooth and precise throttle application. It also offers 90% lower emissions than current two-stroke racing engines.
The 12-inch midsection is all-new and designed specifically for Formula 1 tunnel boat applications, with a structural wet sump driveshaft housing and integrated power trim and lift with remote pumps. 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, so the teams can select the ratio that best fits each particular race.
“The primary purpose of the overdrive is to increase the input speed to the gearcase,” said Mercury Racing Director of Engineering Jeff Broman. “While the 360 APX produces about 45 percent more torque, it doesn’t match the RPM of the 2.5-liter two-stroke. With the new 360 APX we can trade some torque to increase propeller RPM via the overdrive, which will also improve the life span of the gears.”
An evolved version of the Mercury Racing Super Speed Master (IV SSM) outboard gearcase is direct-drive with no neutral or reverse shifting. Above-water exhaust offers unrestricted flow and an exciting tone for racing fans. The motor is equipped with integrated, light-weight steering arms for tunnel boat cable steering. The top cowl and driveshaft housing covers are lightweight carbon-fiber composite. The cowl features robust latching and sealing systems, while the driveshaft cover has quick-release fasteners to ease access to the midsection.
New Engine Oil
Mercury Racing 10W-30 MRX engine oil, a high-performance full-synthetic lubricant, was engineered alongside the 360 APX outboard and specifically formulated to withstand the heat and stress the engine will encounter during F1 tunnel boat competition.
“I am excited about the arrival of a new low-emissions competition outboard engine from Mercury Racing, focused at the top level of powerboat racing,” said UIM President Dr. Raffaele Chiulli. “The engine, designed with input from the UIM and H2O Racing, significantly reduces exhaust emissions while at the same time providing the speed and excitement that powerboat racing fans expect from our flagship series in circuit racing. The UIM supports full implementation of this engine, which demonstrates our commitment to lowering carbon levels in our sport.”
Mercury Racing 360 APX outboards are already available for order and shipments are expected to commence in November 2020.
Rated Horsepower (HP/KW)- 360 / 268
Measured Propshaft Horsepower- 360
Idle RPM- 750
Max RPM Full Throttle- 7000
Cylinders/Engine Configuration- V8 [64 Degree] With Racing-Specific Dual Overhead Cam [DOHC] And 32-Valves
Displacement (CC)- 4573
Displacement (Cubic Inch, CID)- 279
Bore & Stroke (MM)- 92 x 86
Bore & Stroke (IN)- 3.62 x 3.39
Induction System- Short-Runner Intake Manifold With Forced Cold Air Induction
Midsection Design- Circuit Racing Specific 12" Mid Section Direct Mounted With Integral Trim And Lift
Fuel System- Electronic Fuel Injection (EFI) Computer Controlled With O2 And Pressure Feedback
Fuel Requirements- Unleaded Premium 91 Octane Minimum (R+M/2) Or 98 RON 10% Ethanol Maximum
Ignition System- SmartCraft PCM 112 Digital Inductive
Charging Sytem- 85-Amp (1071 Watt)
Starting- 24V Electric Start With SmartStart Protection
Exhaust System- Above Water
Cooling System- Water-Cooled With Thermostat Control And Integrated Pressure Relief
Lubrication System- Structural Wet Sump With Integrated Baffle System And Oil Cooler
Oil Requirement- Mercury Racing High-Performance Synthetic SAE 10W-30
Oil Capacity (Qts)- 7
Oil Capacity (L)- 6.6
Engine Management System- Competition Spec SmartCraft PCM 112
Throttle & Shift Controls- Digital Throttle
Engine Protection System- SmartCraft Engine Guardian With Competition Calibration
Trim/Tilt System- Power Trim And Lift With Remote Pumps
Tilt Range- N/A
Trim Range- 13°
Lift Range- 26Mm (1 in)
Troll Control- N/A
Gearcase- OB IV SSM
Gearcase Ratio- 1.13 (15:17)
Overdrive Ratio- 0.714 (35:25) | 0.739 (23:17)
Overall Drive Ratio- 0.809 | 0.837
Gear Shift- N/A
Dry Weight (Lbs/Kg)- 430 Lbs / 195 Kgs *Dry Weight Refers To Base Engine Without Liquids, Battery Cables, Throttle/Shift Cables, Bolt-On Steering Components, Mounting Hardware, Or Propeller/Hub Kits.
Steering Angle- +/- 30 Degrees
Steering- Cable with Wing Plates
Emissions Level- CARB/EPA 3-Star, EU RCD II
You can get the full breakdown of the new 360 APX with Mercury Racing general manager Stuart Halley and director of engineering Jeff Broman below: