Many people use the terms “cavitation” and “ventilation” regarding a boat propeller’s performance, but far too many folks mix these terms and their meanings. Truth be told, they’re very different phenomenon. Join boats.com US Senior Editor Lenny Rudow in this video, where he explains what each is, why they happen, and what you’ll need to do about it.
The terms are often used interchangeably and often incorrectly, let's look more closely at what they actually mean.
Cavitation if the formation of air bubbles on the propeller. Cavitaion usually occurs as a result of damage and you'll feel it in the form of vibrations.
Cavitation is bad for three reasons. First it can physically damage the propeller. Secondly, it causes those vibrations which makes your ride less comfortable. Thirdly it reduces bite, which reduces efficiency.
Ventilation, on the other hand, is the propeller sucking in air. This may happen because you have the engine trimmed up too high. It can occur because you're jumping waves and the back of the boat is actually coming up near the surface of the water, or perhaps you have a really sharp turn and as the boat leans your propeller is too close to the surface.
Ventilation is also bad mostly because it can cause a radical reduction in thrust and also it can cause your engine to over-rev.
Cavitation and Ventilation how can you tell the difference?
If you can feel vibration and your propeller has visible pitting, you have cavitation and you probably need professional help. If, however, your engine is over-revving you have a ventilation issue and this is usually something you can fix yourself.
Want to learn more about those propellers, how they move your boat forward, and what propeller issues you might encounter? Then be sure to check out Boat propellers: choose the right one and How to change a propeller.