what length shaft is my motor

[curtis45]

Hello,
1973 evinrude model 1155393M. What length is the shaft I think is what I am trying to ask. I am looking to replace this motor and looking at other motors they are stating 20" or 25" shafts.
This is on a pontoon if it matters.
Thanks,
Curtis

 

[F_R]

Has to be 20" because they didn't make any 25" in 1973.

 

[curtis45]

Thank you sir.