---

I have a 1991 merc two stroke 40 hp
the prop on it is a 13P but I do not know the diamter, my top speed on my 13 is 32mph
I am off to a marine fle market in Downtowm Miami in an hour, I know I want a prop with more pitch
What is the ideal prop size I should look for to get that speed up to 38-40mph

---

You probably want a 14" pitch propeller. Do not worry about the diameter because if it fits a two stroke Mercury 40, it will have the appropriate diameter and spline count. Most "C" class propellers are in the 10" to 11" diameter range.

Of course, there is a lot more to fitting a propeller than just pitch and diameter, but on a Sport 13, you can't go too far wrong.

38-40 MPH is a little optimistic. 36-38 is more reasonable and raising the motor on the transom and using a stainless steel propeller will make a huge difference.

---

Thanks for thr reply, the flea market sucked. one guy had a used SS 10 3/4 X 15P cupped prop he offered to me for 40 bucks but he was not sure if it fiot a merc or not so I passed on it, I know a cup adds about 1 to 2 more in pich depending on the cup size and a cupped 15 would probably be way to much

---

All modern outboard propellers are cupped.

---

Good stuff, thanks Now the search goes on for a good used (cheap) 14P alum prop.
If I find one and the speed goes up close to 38-40 then I will invest in a SS prop
I did not know all modern props were cupped, the old one on my motor is not cupped