Help me identify whether I have a 1" or 1 and 1/8" shaft

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Rugglesworth

Petty Officer 2nd Class
Joined
Jul 6, 2023
Messages
183
I have a 93 350 mercruiser ski mag with 1:1 velvet drive in 93 ski ray tournament boat. I'm getting my prop swap on Monday and just realized after I bought a new prop, it's for a 1 and 1/8" prop shaft. I thought that was standard for ski boats but then realized that they used 1" shafts back then as well. So I measured the circumference and it came to 3 and 1/4 " approximately. From my calculations that means it's a 1" shaft and I need to run to the prop shop before it closes today and get a different prop. Can anyone here confirm the prop shaft size from my measurements?

Thanks in advance. we leave next week to the cabin for 3 weeks out of town so this needs to happen today.
 
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airshot

Vice Admiral
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Jul 22, 2008
Messages
5,539
Depends being on how accurate your measuring is....3 1/4" equals a 1.034 dia. Shaft........you need a 3.125 circumference to get closer to a 1" dia.....
 
nola mike

nola mike

Vice Admiral
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Messages
5,528
airshot said:
Depends being on how accurate your measuring is....3 1/4" equals a 1.034 dia. Shaft........you need a 3.125 circumference to get closer to a 1" dia.....
Click to expand...
And if my high school geometry is correct, closer still to 3.1416 😀
 
04fxdwgi25

04fxdwgi25

Chief Petty Officer
Joined
Mar 25, 2022
Messages
605
Instead of guessing, get a cheap vernier caliper. Available anywhere, such as True Value for under $20.
1750583632016.jpeg
 
R

Rugglesworth

Petty Officer 2nd Class
Joined
Jul 6, 2023
Messages
183
thanks y'all. I was right it is a 1" shaft. When I went to the marine shop yesterday asked for a 1" shaft and measured it and it was the same as mine. Glad I figured this out as I had to swap the new prop I just bought for the correct one. The swap is happening first thing tomorrow morning and then we head out to the cabin for 3 weeks shortly after.
 
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