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Counter Rotation Gearcase

Written by Nicholas Kamuda
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Many dual-engine boats commonly include a counter rotation gearcase. Single engine designs usually include propellers that move in a clockwise direction for normal forward motion. For a boat with a twin-engine setup, however, two clockwise propeller rotations can be the source of many steering difficulties.

By using two propellers that both move clockwise, the gearcase can be pulled in the same direction, and torque can cause the boat to roll towards the port side. Without a counter rotation gearcase, the boat can list, forcing the skipper to full attention just to keep a straight course. Especially in high winds and choppy water, keeping a true course on a two-engine boat can present difficulties and potential hazards.

A counter rotation gearcase works by driving the propshaft and attached gear in counterclockwise rotation under normal engine operation. The parts in a counter rotation gearcase are highly specialized, and not fungible with parts from a standard gearcase. They are made for durability and increased strength to handle the pressure of counter rotation.

Purchasing a Counter Rotation Gearcase

If you need to replace your gearcase, there are many informative resources available online that can help. Marine parts stores and outboard forums contain a lot of valuable information, and many parts stores offer help from knowledgeable sales staff as well. Also, be sure to check your manual for information on what gearcase works best with your system.

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