The Specifications for a 25 HP Yamaha Outboard Motor

Written by brianna byrne
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The Specifications for a 25 HP Yamaha Outboard Motor
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Yamaha Motor Corporation has a history stretching back to 1953, when the company began making motorcycle engines. In the years since, Yamaha has expanded to offer a variety of motors, including outboards for boating. In 2010, Yamaha produced three different outboard motors with a net power of about 25 horsepower.

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The Midrange two-cylinder F25 engine has a net horsepower of 25, with a displacement of 30.4 cubic inches, revolutions per minute (RPM) range between 5,000 and 6,000 and a compression ratio of 9.4 to 1. Its alternator output is 13A at wide open throttle (WOT) with a gear ratio of 13 to 27. Additional systems include a single overhead camshaft (SOHC) carb, a wet-sump lubricator, a CDI micro computer ignition and options for both manual or electric starter. The F25 weighs approximately 77.1kg. and received a three-star emissions rating from the California Air Resources Board (CARB).

High Thrust

Designed to maximise power and control, Yamaha's High Thrust line of outboard motors comes in a 25hp model called the T25. This two-cylinder engine has a displacement of 30.4 cubic inches, a compression ratio of 9.5 to 1, a 13A alternator output at WOT and a gear ratio of 12 to 28. Weighing in at 121kg., the motor features an SOHC carb, a wet-sump lubricator, CDI micro computer ignition and an electric starter. Its CARB emissions rating is three stars.


Yamaha's Portable outboards are light and fuel efficient, but still relatively powerful. Though there is no portable engine with exactly 25 horsepower, the F20 Portable is nearly there at 20hp. The two-cylinder engine weighs only 52.2kg. with a displacement of 12.0 cubic inches and a compression ratio of 9.3 to 1. Its alternator output is 10A at WOT, and its gear ratio is 13 to 27. Like the 25hp motors, the F20 Portable comes with CDI micro computer and a wet-sump lubrication system. It also features an SOHC fuel/induction system, a manual or electric starter, and a CARB emissions rating of three stars.

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