outboard propeller slipage

[troppo]

Anyone had experience with the rubber hub in outboard propellers causing some propeller slippage?

I have a 9.8 hp 2-stroke Parsun outboard and had a couple of times when on the plane in my 11 foot dinghy where the motor suddenly revved up then instantly settled down (the boat and motor jolting when that happened) but then everything went back to normal. I suspect I hit something submerged. For example, out on a slightly flooded river yesterday and the motor hit something just under the surface (I suspect a submerged float and rope) and the propeller slipped for a split second. Then it gripped and all was good.

Seeing as it has happened a couple of times now, I thought I should investigate more deeply than my usual cursory inspection. Did Google search and eventually found that the propeller has a rubber hub which is designed to slip rather than break something like a gear. I guess it was that causing the slippage.

The propeller has some small chips on the leading edge and lost paint. Some rub marks that look like I hit some rope. No other damage I can see but the rubber hub could be damaged and I would not know.

The prop came off easy and checking it out, does not look like there is any obvious problem with the rubber hub.

Can you tell me at what point I need to replace the propeller (rubber hub not separately replaceable)? I don't think the propeller is slipping anytime except when it hits something rather substantial. I don't think it is slipping when accelerating quickly to get up onto the plane.

Do these rubber hubs fail quickly or slowly? Since my hub has had some slippage but seems to keep working fine, does that mean it is okay or does it mean I should replace it? For insurance, should I carry a replacement prop and tools?

troppo