I replaced what I believe is an OEM OMC 21p prop on my 1973 115 Evinrude with a Michigan Wheel 13x20p. The boat is a 16ft Dixie Devil Ski Boat. The reason I changed props is because the boat was not able to pull me out of the water when attempting ski behind it. At one point I did have a 115 Chrysler motor with a 19P Au prop that would pull me right out of the water. I was unable to find an inexpensive 19p SS prop, so I went with the 13x20p I have now.
Now, to the specs with two people on board....
With the old prop:
Pitch - 21p
Diameter - ???
Max RPM - 5100
Max Speed - 42MPH (GPS)
With the new prop:
Pitch - 20p
Diameter - 13"
Max RPM - 4900
Max Speed - 41MPH (GPS)
I was expecting to go up in RPM and maybe drop 2-3MPH on the top end. Shows what I know
This newer prop appears to have more surface area on the blades than the old one. Is this why with a smaller pitch, it has less slip?
I haven't tried to ski behind it yet, so I don't know if it will pull me out of the water or not. I suspect it will.
Another strange thing, it has little 3/8" holes drilled into it near the leading edge of the blades. Is this to allow exhaust gas to surround the blade during low RPM operation? What purpose do they serve?
Now, to the specs with two people on board....
With the old prop:
Pitch - 21p
Diameter - ???
Max RPM - 5100
Max Speed - 42MPH (GPS)
With the new prop:
Pitch - 20p
Diameter - 13"
Max RPM - 4900
Max Speed - 41MPH (GPS)
I was expecting to go up in RPM and maybe drop 2-3MPH on the top end. Shows what I know
This newer prop appears to have more surface area on the blades than the old one. Is this why with a smaller pitch, it has less slip?
I haven't tried to ski behind it yet, so I don't know if it will pull me out of the water or not. I suspect it will.
Another strange thing, it has little 3/8" holes drilled into it near the leading edge of the blades. Is this to allow exhaust gas to surround the blade during low RPM operation? What purpose do they serve?
