Does 9 1/2 really mean 9 1/2?

[mnmx3]

I recently acquired a 78 9.9 'rude (M# 10824M) which is now running great after some work on the cooling passages and the lower unit. I have a 9 1/2 x 10 prop installed but it measures 4 1/4 inches from the center of the hub to the furthest tip of the blade. Shouldn't that measurement be 4 3/4 inches? I suspect there is some amount of wear on the prop because the front section of the lower unit was stopped up with sand and scale indicating to me the motor saw some shallow water use. I've since cleaned it out and drilled out the drain hole a little bigger to allow better draining. Thanks in advance for your help.

 

[Bifflefan]

Re: Does 9 1/2 really mean 9 1/2?

If there are large numbers stamped in the hub somewhere, it has been reworked at a prop shop and they have taken some diameter off for some reason.If no numbers, it could still have been done at a prop shop.

 

[steelespike]

Re: Does 9 1/2 really mean 9 1/2?

A prop will wear more in sandy.silty conditions I wouldn't be surprised to find a 32 year old prop to be undersized.

 

[sethjon]

Re: Does 9 1/2 really mean 9 1/2?

I recently acquired a 78 9.9 'rude (M# 10824M) which is now running great after some work on the cooling passages and the lower unit. I have a 9 1/2 x 10 prop installed but it measures 4 1/4 inches from the center of the hub to the furthest tip of the blade. Shouldn't that measurement be 4 3/4 inches? I suspect there is some amount of wear on the prop because the front section of the lower unit was stopped up with sand and scale indicating to me the motor saw some shallow water use. I've since cleaned it out and drilled out the drain hole a little bigger to allow better draining. Thanks in advance for your help.

From your measurement its safe to say its a 91/2. Realize that even its off by a 1/2" you won't be able to tell the difference.

 

[mnmx3]

Re: Does 9 1/2 really mean 9 1/2?

Thanks for the replies. I wasn't planning to change out the current prop anytime soon. I was just curious if the 9 1/2" designation meant the actual diameter should be 9 1/2".