On the left of the photo below is my old Hydrodrive 4LHD
I bought used for $35 when I was 14. It was the 1952 8.5 HP version. This photo, taken in 1968, when I was 21, shows it on a hydroplane after it had gotten dunked by a big wave taken wrong. That motor got dunked several times and kept coming back for more! I built the hydroplane at age 14 with plans from Science and Mechanics Magazine.
Also in the photo is a 1965 V4 60 HP on a 1958 Crestliner Voyager14, and my friend's mid-1950s 25 Gale on a modified Lonestar - Ah the good old days!