Hello Yves,
The black engine is the Hemmens Caton, with 3/8 x 5/8" bore and stroke (9,52 x 15,87 mm). Engine height 3 1/2" (89 mm).
I have seen Caton engines also painted green by the manufacturer.
Obviously, the red engine is the Hemmens Max II - it says so on the label. It has 9,5 x 15,8 mm bore and stroke. Engine height 95 mm. Operating pressure 30-80 psi. Recommended propeller size 4 blade 76 mm.
The Caton is the older engine and I think it evolved into the Max II, which seems to have replaced it, having more features such as integrated lubricator cups with pipes for the crossheads. Bore and stroke seem identical and both engines have piston valves and a piston reverser. The Max II is however somewhat taller and has the pump mounted vertically at one end. The Caton could also have a pump, but was mounted horizontally to one side.