I think if you can't contact a Variprop dealer (and they should answer this in the interest of good public relations), you should experiment
. Four blades have more area than three, but it's the profile of the blade ends that really matter most. You also have to consider if your engine
was operating in its most efficient part of its power band and was working as you expected. This is important in terms of wear and tear and fuel
To give a brief example, on my smaller sailboat, I went from a two-blade 12 x 6 fixed prop on a direct-drive Atomic 4 to a 11.5 x 8 Gori two-blade folding prop.
about a third of a knot
off top-end speed, down to 6.1. I rarely run full throttle, however, as the fuel
cost is not worth the last 3/4 of a knot
I lowered my "dead slow" speed to 1.7 knots from 2.1. This is better for tight places/docking.
Shifting from forward to reverse takes a couple of seconds longer.
Stopping and reversing are enhanced, due to the squared off tips of the Gori. A big plus.
I sail faster due to the reversed drag. How much faster in terms of acceleration impressed me: I harden up and shoot away as opposed to gradually coming up to speed. It's improved my sailing experience far beyond the minor penalty in speed under power. I even use (slightly) less gas, possibly because I rarely exceed half-throttle, which gives me 5 knots on a 33 footer.
So there are a lot of variables. If 14 x 14 with your engine
seemed good, I would try 15 x 12 and make adjustments. But first I would Google
"prop area and pitch calculations" and see if you can test-fly some numbers. If I was a daysailer in a crowded marina, stopping and backing down power would matter more to me than cruising speed. On passage
, the opposite.
You know that with a Variprop you can set different "pitch stops" for forward and reverse, right? Efficient and slippy forward and torquey as hell in reverse for slow, massive water