I am trying to figure out the prop pitch and prop diameter. I bought a prop last year and was on the boat quite a bit.

However yesterday the prop fell off after stopping in a cove.

It's a 50hp outboard motor that came on the 2005 Bentley pontoon 24 ft.

It has a serial number of 1B197906

Then there is another number of 12X22.

The mechanic said something about a gear ratio is 1:83.1

If anyone could help or point me in a direction for the prop pitch and/or diameter too...I would GREATLY appreciate it.

Thanks.

With a 24' boat, I would guess a 17" pitch prop would be about right. Sounds like you had a 22" prop which is too much pitch to turn on a 24' pontoon.