When selecting an engine to power your vessel, conventional wisdom often leads us to focus on engine horsepower (hp) as a primary indicator of boat speed. This approach holds true for gasoline engines and applications with minimal payloads, like motorcycles or cars.

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However, the dynamics change dramatically when it comes to waterborne vessels. Vessels face substantial resistance from the water they displace, necessitating a unique perspective on engine performance. This is where the issue arises with gasoline engines, which typically exhibit low torque. Consequently, to access 30% power from a gasoline outbaord, you often find yourself revving up the engine to circa 60% of its capacity.

 

In fact, it’s common to experience a noticeable increase in engine power only when you surpass the 70% mark on the throttle.

This predicament becomes even more pronounced when dealing with heavier vessels, where the engine may struggle to exceed 70% to 90% of its maximum rpm due to a lack of torque. Consequently, what you believed to be a 90hp outboard engine may effectively deliver only 65hp in real-world applications.