Pensacola Blue Angels
Bass Page
hook1. com

Proper Propeller Selection :

One of the most asked questions is "Which prop is best for my boat?"
Well, unfortunately, that is an impossible question to answer without good quality testing. The point is this...if there was one perfect prop in the world, everybody would own it.
It just doesn't exist. Here's the skinny on the piece that shakes the lake.
With all things being equal, the fewer blades a propeller has, the faster the propeller will
run. In the 60s and early 70s, two blade propellers were commonplace. However, they
vibrated and had other various drawbacks. Three blade propellers solved the vibration
problem, but the drawback was they were slightly slower than two blades. Four and five
blades have brought about the same speed issues. As in most things, however, there
are exceptions. Boat weight and design has a lot to do with it. A heavier boat may
need the added blade area of a four blade propeller to provide much needed bow lift,
where as a lighter boat will provide its own lift and can make do with a three blade.
Blade shape also makes a difference. A round eared propeller will typically provide better bow lift and will be more efficient (less slippage) than a pointy-eared cleaver or
semi-cleaver propeller. The drawback is (there's always a drawback) to a round ear prop is that they typically have more torque on the wheel than a cleaver or semi-leaver. Round ear props tend to lift the bow of the boat where as a cleaver will raise the stern of the boat and a semi cleaver will have very neutral lift characteristics. If you're boat runs good on top end, but has a little trouble getting out of the hole, have your prop shop "roll the leading edge." This is a process of decreasing the pitch on the first couple of inches of blade closest to the hub. This works best on high performance boats that can surface the propeller. At low speeds the prop is completely submerged and will "think" it's a lower pitch prop. At high speeds, only the outside half of the prop is really working and the prop is the standard pitch on the tips, so the prop "thinks" it's still the original pitch.
The drawback is a slightly reduced top speed in many applications. Finally, the issue of through hub exhaust, over hub exhaust, and over/through hub exhaust propellers is an interesting issue. Lighter boats typically will run fastest with an over hub exhaust prop. Their drawback is higher than usual cavitation at take off due to the exhaust flooding the blades. Heavier boats typically need a true through hub exhaust propeller or else the propeller will cavitate so badly, the boat will not plane.
Bass boats typically work well with the over/through hub. This is a good combination of
the other two styles. These propellers (OMC's Renegade and Mercury's Trophy small
hub are good examples) allow some of the exhaust to help break the prop loose at take
off, but won't flood the prop causing it to cavitate mercilessly.

HOME