As i recall, a 25 hp was the largest one Evinrude made back then.
I had a 1954 Mark 55 Mercury 4 cylinder 40 hp which was the largest Merk back then.
Traded that for a 56 Johnson 33 maybe 35 hp (with electric start), which was also then the largest.
And the boats were mostly wood or aluminum, as the f/g ones were just starting to show up.
