ZF Marine’s new two-speed outboard transmission
By Mike Brezonick25 March 2021
ZF Marine presented a new two-speed transmission as part of the new Verado Outboard engine developed by Mercury Marine.
ZF Marine called the transmission for this application an industry first and explained that it is the result of a four-year collaboration with Mercury Marine. Production of the new transmission has begun at ZF’s factory in Padua, Italy, the marine production facility for pleasure craft applications.
Mercury Marine recently launched 7.6-L Verado outboard, a 12-cilinder vee configuration with an output power of 600 hp (447 kW).
Two-speed technology for marine applications is a well-known concept by ZF but was never applied to outboard applications before. ZF Marine explained that the new solution allows for perfect matching of engine characteristics to different operating modes. In this particular case, the two-speed transmission delivers maximum torque and acceleration in the first gear, and then silently shifts to the second gear for cruising efficiency and thrilling top speed, the company said.
The transmission includes a three-vertical wet clutch layout and shifting is driven by proportional valves, granting unmatchable trolling capabilities at low speed, as well as an almost unperceptible shifting between the two gears, ZF said. The proportional valves also optimize vessel performance during docking and maneuvering, making every movement more precise and smooth, especially in combination with a joystick control system.
According to ZF Marine, every marine application, regardless of the operative mode, can benefit from two-speed transmission technology, as it improves the propulsion performance by matching the engine power and the vessel (or propeller) power demand. More acceleration and efficiency, less noise and more thrust for towing activities could be achieved by selecting the proper reduction ratio for each gear. “First gear is 20% lower than second gear, which generates high propeller torque, and the ability to accelerate the boat and get it on plane quickly,” said Tim Reid, vice president of Product Development and Engineering at Mercury Marine. “The engine continues to deliver power and accelerations through its power shift, all the way to rated speed,”