What you need to know about 'tweaking' your propellers By Capt. I have been aboard boats that were impossible to stop by reversing the engine, and other boats with engines that refused to come up to proper operating speed.
Engines turning the wrong-sized propeller are common.
Too large a propeller overloads an engine, requiring more power than the engine can produce. The correct propeller selection is probably the most important factor in any marine engine installation. Here is a quick method to see how your propeller relates to your engine, reduction gear and hull. Generally, a larger propeller diameter produces greater thrust, and will offer better slow-speed handling characteristics. Owners of higher-speed vessels will find smaller prop diameters more efficient.