Re: Surgery without a manual
If that is indeed a 1955 Evinrude 7.5 hp it does not have a shift disconnect window. However, removing the powerhead is easy. Don't let it scare you. Once you get it off, check the lower powerhead seal and change the impeller.
Post the model number. I may have a pdf copy of the parts manual for this engine. Send me your email address via PM and I'll sent it to you tonight.