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Prop slippage
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| Reel Easy |
Posted on 07/24/14 - 6:19 AM
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While hammering the throtttle pulling adult skier out of the water, the engines reved very high for a moment then resumed normal revolutions. Might this be from prop slippage and if so might it be resolved with different props.
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| Phil T |
Posted on 07/24/14 - 7:07 AM
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It could be ventilation or the hub slipping. Can reproduce the event or is it a one time event?
Check the hub insert on the prop first.
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| Reel Easy |
Posted on 07/24/14 - 7:30 AM
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Thanks Phil: Yes, it did repeat. I'm not sure if prop slippage is possible or something that I made up. If it were the hub, why would the revving be momentary and then stop? It seems to me that the slippage would continue until you throttle back.
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| dbcollen |
Posted on 07/24/14 - 8:11 AM
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You probably just ventilated the prop.
-Dustin |
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| Reel Easy |
Posted on 07/24/14 - 11:18 AM
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Dustin: Can you explain ventilating?
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| Phil T |
Posted on 07/24/14 - 1:05 PM
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ventilation is when your propeller drags air from above the water into the blade.
You know your propeller is ventilating when your forward speed drops as the engine revs up suddenly
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| Ric232 |
Posted on 07/24/14 - 8:01 PM
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Phil T wrote:
ventilation is when your propeller drags air from above the water into the blade.
. . . thereby causing severe prop slippage.
Ric
2008 130 Sport
Merc 40hp 4-stroke |
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| lost sailor |
Posted on 07/25/14 - 6:54 AM
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ventilation is when your propeller drags air from above the water into the blade.
You know your propeller is ventilating when your forward speed drops as the engine revs up suddenly
Perhaps I'm misinformed but I thought that's what cavitation was? Like when taking a sharp turn at too high of a speed and the boat slows as the engine revs higher...
1990 Outrage 17 I - 1990 Evinrude 120 |
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| tmann45 |
Posted on 07/25/14 - 7:29 AM
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lost sailor wrote:
ventilation is when your propeller drags air from above the water into the blade.
You know your propeller is ventilating when your forward speed drops as the engine revs up suddenly
Perhaps I'm misinformed but I thought that's what cavitation was? Like when taking a sharp turn at too high of a speed and the boat slows as the engine revs higher...
Cavitation is misused very often when it is actually ventilation as described very well above. And the flat plat above your propeller is better described as an anti-ventilation plate.
Cavitation is as per:
Merriam-Webster - the formation of partial vacuums in a liquid by a swiftly moving solid body (as a propeller) or by high-intensity sound waves; also : the pitting and wearing away of solid surfaces (as of metal or concrete) as a result of the collapse of these vacuums in surrounding liquid
Wiki - the formation of vapour cavities in a liquid – i.e. small liquid-free zones ("bubbles" or "voids") – that are the consequence of forces acting upon the liquid. It usually occurs when a liquid is subjected to rapid changes of pressure that cause the formation of cavities where the pressure is relatively low. When subjected to higher pressure, the voids implode and can generate an intense shockwave
There is no sucking of air from above the water level in cavitation.
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