Cavitation

[Krugel]

We are busy with a Aluminium Barge, It has a 85HP Yamaha on.

Problem is that the Prop Cavitates under hard acceleration.

Will changing the Prop (Picth) help?

Any suggestions?

 

[Krugel]

What is the main causes of cavitation?

 

[Limpopoking]

There's a difference between Cavitation and Aeration... Cavitation is when a prop is asked to do more than it possibly can. So too much power on a prop with too much pitch, trying to push a boat that's too heavy will cause cavitation. Cavitation is when the negative pressure behind the prop (vacuum) gets high enough to expand the air molecules in the water. The air pockets of low pressure then implode, making a noise and sometimes damaging a prop.

More common in boats is aeration where air is introduced into the water around the prop. The air could be coming from the hull (via strakes or hull damage... only really noticeable with planing hulls) but it's usually sucked in from around the cavitation plate of the motor.

Changing to a lower pitch will help in both situations. In your case, it may also help to have your motor set a little deeper in the water. Start by lowering the pitch of the prop. Try to borrow one before rushing out an buying. You could also solve the problem with more gentle acceleration.

 

[Krugel]

Limpopoking wrote:

There's a difference between Cavitation and Aeration... Cavitation is when a prop is asked to do more than it possibly can. So too much power on a prop with too much pitch, trying to push a boat that's too heavy will cause cavitation. Cavitation is when the negative pressure behind the prop (vacuum) gets high enough to expand the air molecules in the water. The air pockets of low pressure then implode, making a noise and sometimes damaging a prop.

More common in boats is aeration where air is introduced into the water around the prop. The air could be coming from the hull (via strakes or hull damage... only really noticeable with planing hulls) but it's usually sucked in from around the cavitation plate of the motor.

Changing to a lower pitch will help in both situations. In your case, it may also help to have your motor set a little deeper in the water. Start by lowering the pitch of the prop. Try to borrow one before rushing out an buying. You could also solve the problem with more gentle acceleration.

Baie Dankie

 

[QuQ]

I would start by lowering the motor by one or even two holes.

 

[yacoob]

Limpopoking wrote:

There's a difference between Cavitation and Aeration... Cavitation is when a prop is asked to do more than it possibly can. So too much power on a prop with too much pitch, trying to push a boat that's too heavy will cause cavitation. Cavitation is when the negative pressure behind the prop (vacuum) gets high enough to expand the air molecules in the water. The air pockets of low pressure then implode, making a noise and sometimes damaging a prop.

More common in boats is aeration where air is introduced into the water around the prop. The air could be coming from the hull (via strakes or hull damage... only really noticeable with planing hulls) but it's usually sucked in from around the cavitation plate of the motor.

Changing to a lower pitch will help in both situations. In your case, it may also help to have your motor set a little deeper in the water. Start by lowering the pitch of the prop. Try to borrow one before rushing out an buying. You could also solve the problem with more gentle acceleration.