Alex,
I understand your problem, did you sharpen and balance them only?
I think you picked the ones with too much pitch ratio and too much
cup in the trailing edge for your set ups. I like the 1715, 1815 on my
21-Hydros personally. I like to run the 17 degree rake ones in the Spring
and Fall and the 19 degree rake ones in the mid summer season. The
17/45% have 7% more blade area and throw more water and load the
engine more. They are also the ones that were designed for electric boats.
I am not a big fan of running a lot of trailing edge cup on our boats because
it kills RPM. If you run the older series propellers and are happy with their
performance then I would use what works well on your set ups. Sometimes
you need to lower the strut depth a little more with the new series propellers
because of less transom lift. With my GT-21 the 1815 works very well in heat
race trim. I believe the set up with some of the 21-Hydros may need more
adjustments to let these higher rake propellers do their job they were designed
to do. Nothing wrong with learning about propellers and how they work. Just have
a good pitch gauge so you can measure them accurately.
Have Fun Testing,
Mark Sholund