Posts: 3508
Location: Elk River, Minnesota | Hiya,
In many cases, going to a semi-cleaver propeller without any tip cupping will result in more slip. In the Yamaha stock steel (black stainless) they have a touch of tip cupping, which I actually ran for a while and liked it, although it lacked speed at the same RPM levels as the ballistic propeller I also carried. That was due to the extra slip created by the blade design and lack of any sort of rear edge cupping on the blade. A little rear edge cupping on that style prop would do even better, although the more rear edge cupping you have, the harder it is to lift the bow since the stern receives so much lifting, forcing the bow down.
If you are looking for mid range cruising without the porpoise, I feel a 4-blade design of some sort would be in order. in most cases, running 4 blades requires a drop in pitch by about 2 inches from what you might turn on a 3 blade prop due to the increased surface area in the water of the 4th blade.
In many cases, running at mid-range requires you to trim down a bit from what you might use at full throttle. The reason for this is the balance of the boat required vs the rpm level you are looking to run at. In many cases, your trim angle might be less than half the amount you use at full throttle. The goal overall is to get a boat that just floats along at midrange speeds.
The Amita 4 you have on the classifieds seems like it would be a fairly ideal prop unless it is over pitched and/or has too large of a diameter. If it is over pitched the porpoising would become an issue at various RPM levels since the power of the boat cannot overcome the extra grip the 4th blade provides. I noticed you mentioned you tried it just a few times.... what did you have on before you tried the amita and in what pitch and diameter?
Tough thing in all prop choices is finding the one that best suits your needs, which usually takes trying out various props of multiple designs. Usually there is going to be a compromise somewhere along the line be it in speed, handling, hole-shot, etc....all dependent on what you are looking to get your rig to do well. In the whole process, though, one prop will stand above the rest in what you are looking for. It is amazing when you dial it in... The boat will do everything you want it to do, and do it with ease.
Steve
Edited by VMS 9/28/2011 1:11 PM
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