Prop hub slipping?

[jonny rotten]

I'm wondering how a prop hub slips. It's locked together with groves and pressed into the prop. It seems like it would either work or not work. Once something blows out the shaft would just spin with any kind of load on the prop especially getting out of the hole?

The reason I ask is my engine seems to be revving higher without the same forward movement at mid and high range and I got over 5000 RPM's without hitting wide open throttle my last trip out....close but not wide open. Speed was good just higher revving. I've never gotten over 5000 at WOT before.

It got out of the hole fine and felt no slipping as in high low RMP. At all speed ranges it's smooth just higher revs than I've ever gotten before.
I've bottomed out plenty of times as I boat in shallow sandy bottom water so a hub blowing out would be the likely culprit. Wondering if it could be anything else if it's not "slipping"
Mercruiser 4.3 Alpha one gen one

 

[Chris1956]

A prop hub is a sleeve or rubber between the brass prop hub and the prop housing. It is made to slip, if the prop hits something. It does often have residual friction, even after it slips initially.

It is not like a shear (drive) pin, where once it snaps, the prop turns free,

If you have a bad prop hub, it will get worse. Soon you will only move forward at idle speed, or less.

 

[hugh g]

I'm wondering how a prop hub slips. It's locked together with groves and pressed into the prop. It seems like it would either work or not work. Once something blows out the shaft would just spin with any kind of load on the prop especially getting out of the hole?

The reason I ask is my engine seems to be revving higher without the same forward movement at mid and high range and I got over 5000 RPM's without hitting wide open throttle my last trip out....close but not wide open. Speed was good just higher revving. I've never gotten over 5000 at WOT before.

It got out of the hole fine and felt no slipping as in high low RMP. At all speed ranges it's smooth just higher revs than I've ever gotten before.
I've bottomed out plenty of times as I boat in shallow sandy bottom water so a hub blowing out would be the likely culprit. Wondering if it could be anything else if it's not "slipping"
Mercruiser 4.3 Alpha one gen one

Change the prop & see what happens.

 

[mr 88]

^ or make a mark from the outside of the hub to the inner making sure you make contact with everything, a yellow or white marking pen from a auto parts store works great as they have a fine point. After your done for the day or after you put it through its paces check the line.

 

[crazy charlie]

Does not sound like a spun hub to me or even any slippage at all.It would be happening when under load when you are throttling up.You probably missed a meal and went out alone without fueling up....Thus higher rpms.Charlie

 

[mike_i]

Do what mr 88 said to test for a spun prop.