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whats make my prop do this?

2.2K views 22 replies 12 participants last post by  ben  
#1 ·
what making my prop get pited up like this it like the water is eating up. what can i do to fix it. my boat is a 1870 weldbuilt tunnel hull
 

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#7 ·
That is from true cavitation... actually inertial cavitation in your case. A low pressure area is being formed which creates a space in the water. As the vacuum space returns to normal pressure, the space collapses and a shock wave is created which is damaging to the metal. This is where your pitting is coming from.

Something is creating this, I once had this happen half way up the blades on my ski boat prop. The culprit was a slightly bent skeg. I straightened the skeg and the 'pitting' went away. Before I straightened it, I could spray paint the prop and run it one time and the paint would be gone in the pitted area. After straightening the skeg, the paint stayed on.

You have something that is creating the vacuum around your prop. Either a deformity on your outboards foot or on the prop. If it is only on one blade, something is wrong with that blade on your prop. If it is on all 3, the problem is on your foot or gear housing.

:tu:
 
#9 · (Edited)
He does...Way better than me..I knew it was cavitation but there was no way I coulda explained it as well as him and identified the specific type of cavitation.
Cavitation often eats up pump impellars when a pump is pumping something with entrained air or if it doesn't have enough head pressure.
 
#20 ·
The tunnel hull traps the air under the boat then directs it directly to the prop. air entrapped in the water is almost as bad as sand in the water. The best way to correct this is with a jackplate and run the motor as deep as you can at higher speeds then shallower when your at low speeds or shooting when your not forceing air under the hull. :co: