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OVERSIZING Propellers - Pros & Cons ☝️| Ask The Expert with NIGEL CALDER
October 11, 2025 · 3 min · 10K views
What this video covers
Nigel Calder explains the trade-offs of running an oversized propeller on a sailboat, responding to a student who discovered their 19×14-inch prop was far larger than the calculator-recommended 17×10-inch.▶ 0:14 An oversized prop reduces wide-open-throttle speed and loads the engine more heavily at lower boat speeds.▶ 1:02 On a sailboat where the engine rarely runs at full throttle, that loading improves fuel efficiency and reduces carbon buildup in the engine — benefits Calder says he applies on his own boat.▶ 1:16 On a powerboat run at wide-open throttle for extended periods, the same oversized prop will overheat the engine and risk serious damage.▶ 1:27 The deciding factor is duty cycle.▶ 1:38 On prop condition, Calder cites his own testing: a propeller left in the water for one month accumulated minor barnacle growth that drove fuel consumption up 50% or cut speed by roughly one knot at a fixed throttle setting.▶ 2:06 He concludes that testing a damaged or fouled prop produces unreliable data, and that prop degradation alone can meaningfully raise fuel consumption — making replacement worthwhile.▶ 3:00
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