Re: Prop Diameter
You can't consider prop diameter alone. The diameter, together with pitch and the rpm of the outboard, is how the prop (and boat) performs.<br /><br />A change in pitch will always have a greater affect on speed and holeshot than a similar change in diameter, kind of what bmurray said.<br /><br />I like to think of pitch as the component that controls power, and diameter as the component that controls rpm...or speed. But you must have a combination of both for maximum performance. <br /><br />Remember, outboards don't have variable or automatic transmissions. And they don't have variable pitch props (like an airplane). So the object is to get maximum speed for your load exactly where the outboard rpm makes its maximum power. <br /><br />For example, maximizing hole shot always sacrafices top end speed because power is usually obtained by decreasing pitch size (and slightly increasing diameter). In other words the outboard stays in low gear and will most likely over-rev on step at full throttle. <br /><br />Maximizing top speed usually sacrafices holeshot because speed is usually achieved by increasing pitch size (and slightly decreasing diameter). In other words the outboard is stuck in high gear and most likely can't obtain power quickly upon accelleration.<br /><br />If an outboard makes its maximum power at 5500 rpm, then that is exactly where you want to maximize your speed for your given load. You must try different props until you find the most efficient prop.<br /><br />The difference in 3 vs. 4-bladed props depend on many factors and your use of the boat. Usually a 4-bladed prop increases bow lift and enhances cornering and stability in high horsepower, high speed boats. A 4-bladed prop does not necessarily increase speed, but rather enhances the characteristics of the boat at that speed.<br /><br />There's cupped props, cambered props, 4-blade, 3-blade, stainless, aluminum, composite, etc. etc. One in a particular size will work the best for your boat. Unfortunately, you need to try them to find which one works the best....and they are very expensive. <br /><br />So for the average Joe, factory props are usually a compromise which includes good solid performance under most conditions. For those who want to split hairs and pick up a mph or two, its just a matter of money.
