Hubs are purchased separately from props. NOTE: Mercury and Turning Point both offer modular hubs and propellers. If you prefer a Mercury product, use the Quicksilver Propeller Selection Guide. You can do this by speaking with an associate at one of our stores, calling our Technical Sales Department at 1-800-BOATING, using the Turning Point Prop Wizard. After processing this information, you can make a better-informed decision. Regardless of the brand you prefer, you will need to gather as much information as possible (see below) to make the best selection. Choices include propellers and hubs made by Mercury (Quicksilver) and Turning Point. We stock propellers to fit most outboards and sterndrives. Cavitation can also occur from thru-hulls, sensors, or other turbulence-producing protrusions under the boat forward of the prop. Causes of cavitation include incorrect engine height (outboards), dings or sharp corners in the leading edge, poor polishing, too much cup or crummy blade design. Many propellers partially cavitate during normal operation, but excessive cavitation may result in “cavitation burn,” metal erosion or pitting of the prop’s blade surface. Ventilation can also occur from prop designs that are not matched to the application, poorly designed props, props with little or no cup, or props that are worn or have damaged edges or cup profiles.Ĭavitation: Often confused with ventilation, cavitation results from water vaporizing or “boiling” due to the extreme lack of pressure on the back of the propeller blade. Ventilation results from excessively tight turns, a motor that is mounted too high on the transom, or an engine that is over trimmed. The boat’s speed drops, the engine over-revs and screams, and the prop sucks air. Ventilation: This problem occurs when air from the surface or exhaust gas from the engine gets drawn into the prop’s blades. There are two ways you can tailor your prop’s pitch to match a variety of conditions: carry two complete props or two modular props with different pitch. If you change configurations, sometimes running light and other times loaded with camping equipment, two props with different pitches make sense. Weight: Your boat may have a lot of heavy gear inside, or you may sometimes use it to tow skiers or wakeboarders, in which case the original-equipment prop may have too much pitch, causing your engine’s rpm to be on the low side.
You can partially compensate for this decrease in performance by carrying a second prop with reduced pitch, making it easier for the engine to achieve the correct rpm at WOT. Reduced concentrations of oxygen at high altitude cause engines to produce less power (about 20 percent less at 7000'). If your engine is over revving, consider a propeller with more pitch.Įlevation: Many small, trailered boats are used at vastly different elevations, such as high mountain lakes and bays at sea level. Going back to the question of performance at WOT, if your engine is under revving, consider a propeller with less pitch. Conversely, a two-inch decrease in pitch will result in an increase of 300 to 400 rpm. As a general rule, a two-inch increase in pitch will result in a reduction of 300 to 400 rpm. Increasing the pitch will decrease engine rpms and decreasing the pitch will increase engine rpms.
Should you "pitch up" or "pitch down"?Įngine rpms and pitch are inversely related. Over revving or under revving can be corrected by selecting a prop with a different pitch. Allowing your engine to under rev or over rev at WOT can result in engine damage.
#14x11 inboard propeller manual#
Your owner’s manual should include this spec-usually 5000–5500rpm for an outboard or 4200-5000rpm for a sterndrive-or your mechanic or dealer may know. Selecting the correct prop should result in your engine running within the designed rpm range at Wide Open Throttle (WOT). Is your boat sluggish coming out of the hole and slow to get on a plane? Are you not hitting the top speed you think you should? Do you want an improvement in fuel economy? Hoping for better all-around performance? Is your current prop blowing out or ventilating excessively in turns or when you accelerate? Are you looking to improve your boat’s watersports performance for tubing, skiing or wakeboarding? Once you have defined your goals, you can move on in the selection process.
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