"Ok, threw the numbers into my
"Ok, threw the numbers into my prop calculator. According to the Nissan specs you should be looking for an "optimum" WOT RPM of 5500-5600. That will allow you to develop maximum horsepower and get the best fuel economy.
Given the boat you have it mounted on, and allowances for gas, battery, gear etc, I also allowed for 4 passengers. (more on that further down)
Given all that data, it recommends a 13D 17P 3 blade propeller.
The closest OEM prop would be a 12.9D 17.6P Nissan product number 3B7-64541-0. A cross match number from Michigan Wheel would be 142012. With either of those numbers it could be further cross matched to the numerous propeller choices on the market today.
That should be your starting point. If you carry less than 4 people on board most of the time and go light on gear, you can probably up pitch by 1 or so, to an 18 or even maybe 19 pitch. Each increase in pitch by 1" usually lowers your RPM by about 200.
If you use the boat to waterski, and are looking for that "great hole shot" you may want to consider a 4 blade prop. It will get you out of the hole quicker, on plane faster and keep you on plane at a lower speed than a 3 blade, but you lose out on top end speed.
There is always a trade off. If you use a 4 blade, you generally select something 1/2" in pitch (less) than a 3 blade to compensate for the additional drag of the fourth blade.
Also, if you use a cupped blade (regardless of whether it's 3 or 4 blades), you subtract another 1/2" of pitch.
So, given the recommdation of a 17 pitch from the prop calculator. As an example, if you wanted to run a "cupped 4 blade" you would select a 16 pitch to account for the extra blade and the cupping.
These calculations are specific to your particular set-up. "Bob" may the same boat as you, and run a 20 pitch - but maybe "bob" always runs at 1/4 tank of gas, doesn't carry a battery and goes out by himself with little gear on board. The above numbers should realistically represent your situation.
Hope this helps - any others questions, don't hesitate to get ahold of me..."
