Prop hub spin - is any slippage normal?

[3lowdown]

1996 Thompson, 7.4 Mercruiser Bravo One, with mirage prop. Last summer with boat loaded and running mid throttle, boat came down off plane and engine revved. I reduced to idle and tried to re-plane but it free revved again. Idled home and parked it. Ever since that episode, it has planed normally (but never had more than two in the boat). I put sharpie marks on the shaft nut and prop housing this spring, and it has only spun about 1/8 turn since that incident.
Is this at all 'normal'? I suspect the hub bushing needs to be replaced - is that something that could be attempted with the boat in the water on a lift? I don't have a trailer - the boat is parked on a lift.

 

[Stinnett21]

No prop slipping is not normal. Your prop needs to be removed and taken to a prop shop to have a new hub pressed in.

 

[Canufixit2]

If the hub is slipping - needs a new hub (New AL prop may be a better $$ choice.). However - it is possible that Weeds or something got wrapped on the prop - which later fell off when you stopped/backed up. I'd Try Pulling a single ski skier - then you will know for sure ....

 

[Texasmark]

I'll go with Canu..........Keep tabs on your marks and if it keeps creeping, do as others said......

For the price of an alum. prop on here you might get a repair estimate and compare. Other thing is you are spending your money on a new prop....not a reworked prop. I know prop shops balance the blades and all, but having spent Sundays boating and Monday lunch hour over at the prop shop, repair is just that....repair.....the rest of the story is that the following year OMC came out with their new Stainless Steel Teflon prop for the large gear case engines and that solved my visit to the prop shop issue.

 

[Chris1956]

The BBC's have been known to spin props. You should try to be careful if the prop ventilates (and revs up), and then catches the water again, like when jumping waves. That roll on of revs and power can overpower the prop hub.

 

[Texasmark]

The BBC's have been known to spin props. You should try to be careful if the prop ventilates (and revs up), and then catches the water again, like when jumping waves. That roll on of revs and power can overpower the prop hub.

Not onto the story to which you eluded but just a few days ago was a posting about a twisted drive or prop shaft from the same kind of action.....Just happened to be a go-fast boat with a very large HP engine. One would imagine that the prop was an exhaust over the hub with no shearing device....I think the engine was on the order of 500 HP.