By: Scott Way
Like their larger counterparts, the new 200 APX will be also a four stroke, but will come in a V6 configuration with over 200 horsepower and a double-overhead/four-valve architecture producing up to 6800 rpm. The compression ratio will be boosted to a sizeable 11:1 with an evolved Mercury Super Speed Master (IV SSM) outboard gearcase with direct drive and no neutral or reverse shifting.
Most notably, the new 200 APX powerplant has 50% reduced exhaust emissions compared to the previous Mercury Racing 200 XS OptiMax engine, and 90% fewer emissions than the legacy SST 120 model.
According to Stuart Halley, Mercury Racing general manager, “The new 200 APX is designed to deliver outstanding performance while reducing the cost of maintenance and fuel for race teams. Mercury Racing is also striving to produce high‑performance and competition engines that keep emissions to a minimum, and the 200 APX helps push that effort forward.”
The 200 APX will be Mercury Racing's first V6 four stroke, and is based on the Mercury Marine 3.4 litre double-overhead cam/four-valve powerhead that uses a 64-degree cylinder angle. The 200 APX will also run at higher compression (11:1 as opposed to 10:1) and will carry a higher peak RPM at 6800 from the previous 5800 maximum. Cold air induction via the carbon fiber cowl will serve as the primary cooling system, and above‑water exhaust will offer unrestricted flow and an exciting tone for racing fans. An updated version of the Mercury Racing Super Speed Master (IV SSM) outboard gearcase will offer direct‑drive with no neutral or reverse shifting, and a lightweight flywheel will allow the engine to rev quicker, and higher, than a stock Mercury engine. The 200 APX will also use the same 12-inch midsection as the 360 APX V8 and will have a carbon fiber driveshaft cover with quick-release fasteners for easy access to the midsection. A structural wet sump driveshaft and integrated power trim and lift with remote pumps is standard, as well as integrated lightweight steering arms for tunnel boat cable steering.
To increase the necessary propeller speed to match the current 8000 RPM two-stroke outboard used in F2 and OPC, an overdrive spur gearset is used to increase the input shaft speed to the gearcase and produce the necessary left-hand propeller rotation.
The new 200 APX will run on premium 91-octane fuel (98 RON w/E10 max), and with a digital throttle control and a 24-volt starting system. The engine is also optimized with Mercury Racing's own 10W-30 MRX high performance synthetic engine oil specifically designed to tolerate the stresses of tunnel boat racing.
“The 200 APX produces about 20% more torque than the two‑stroke motor, but at a lower RPM,” said Mercury Racing Director of Engineering Jeff Broman. “With the overdrive gearset we can swap some of that torque to increase propeller RPM, which allows most teams the opportunity to use the same propellers they have been fitting to the two‑stroke motor — a big cost savings for the race teams.”
As for both the UIM F2 and APBA OPC circuits, racers compete inside carbon fiber tunnel boats measuring 16 feet (4.8 meters) long that weigh just 1100 pounds (510 kg) including driver and engine. F2 boats are capable of top speeds up to 120 mph (190 km/h) and can accelerate from 0 to 60 mph in as little as 5 seconds. Up to 20 boats race the course at a time making tight turns while dodging one another in one of boating's most high-paced and exciting spectacles.
The 200 APX will be available to qualified race teams starting in May 2021. You can get a full technical overview of the new engine in the video below: