Reply To: Mid 1950’s 10 to 18 horse lower units

[Don]

OK, wasn’t aware that gear ratios were different, but perhaps.  So that means you can use the 15-25hp models 22CI gear cases from the around 1956-1976.    You are not limited to using the same model year as you have, 1958.    But again, be sure to note the model year of the gearcase you are using to replace yours, and consult that year’s parts manual for future repair parts…