Over the past 15 years or so, I have assembled a registry of
sorts for engines built by the Hercules Gas Engine Co. at
Evansville, Ind. The registry starts with engines produced in 1914.
At last count there were 3,682 engines on the list, consisting of
engines I have seen or have been reported to me.
Many people think Hercules-built engines are simple, look-alike
engines. The engines with a 3-1/4-inch bore by 5-inch stroke are,
by far, the most common size, and the variations are numerous.
There were likely some 140,000 of this size built. The chart at
right shows a breakdown of the brands produced by Hercules and the
number of 3-1/4-inch x 5-inch size engines on my list to date:
Despite all the variations, you could throw most of the parts
into a pile and build up a mix and match engine. This is what makes
it hard to properly identify some engines in the Hercules line,
because frequently someone has already mixed and matched parts.
Hercules Registry Breakdown/Larger Engines
Bore and stroke
2, 2-1/4 and 2-1/2
2-1/2, 2-3/4, 3,
5 and 6
7 and 8
9 and 10
12 and 14
This listing does not include 32 of the 1-1/2 HP Sparta
Economy-style engines built in Evansville. Nor does it include 31
of the 1-1/2 HP D models. The 3-1/2-inch x 4-inch 1-1/2 HP Model N
is not included either. There are 68 of them on the list.
Hercules Registry Breakdown by Brand 3-1/4 x 5 Bore and
When all the variations among the engines on this list are
considered, it becomes mind boggling to sort them all out. Between
1914 and 1929 there were nine different Hercules models produce,
eight different Economy models, four different Jaegers and four
different ARCOs. Many of these models look almost alike, but that
is where the fun comes in, because within these models are numerous
variations or special adaptations.
Did you ever see a 1-3/4 HP SK Hercules? If you have, did you
ever see an SK Hercules with an air-cooled head? Did you ever see a
Hercules with a two-piece frame? Did you ever see a
Hercules/Economy with a natural gas mixer? Did you ever see a
Jaeger with the spark plug in the head? Did you ever see an ARCO
with a hopper-shaped fuel tank mounted to the side of the water
hopper? Did you ever see an early Hercules with a sheet metal crank
guard? These are just hints of the oddities that occur.
To round out the rest of the 3,682 engines I have also included
a breakdown of the larger engines.
Add to all of this 215 X Models, 169 J Models and 125 Thermoils.
I hope all these numbers aren’t confusing, but when someone
talks about collecting one of everything in one of the
Hercules-built brands or sizes, it becomes a challenging and never
Glenn Karch is a noted authority on Hercules engines.
Contact him at: 20601 Old State Rd, Haubstadt, lN 47639, or e-mail