The 1952 Johnson/evinrude 25hp is not capable of attaching to an electric starter. OMC first used an electric starter on the RDE-16 model in 1954. There was an aftermarket electric starter for the 1952-3 RD but it’s very crude and uncommon. Since this aftermarket starter was chain driven, the recoil has to be removed for operation, meaning that when the electric start doesn’t work, all 12 screws on those round shrouds have to come off to use the sheave pull.

Electric start was offered on some evinrude/elto motors starting in 1929-30.

You can use just the powerhead of a 1954 25hp which would give you the proper mounting holes for the electric start, but in reality its probably easiest to hold out for a 1954 RDE-16. I will add pictures tomorrow to show how/why the earlier RD motors cannot mount an electric starter..