20601 Old State Road, Haubstadt, Indiana 47639
Beginning with the fall 1921 Sears catalog, slightly modified
and re-rated Thermoils were offered. They were the model UA now
rated at 7 and 9 HP; however, there were no changes in the bore,
stroke or engine speed from previous U models. There were only
three noticeable changes. The combination oiler and fuel previously
attached to the rear of the water hopper was gone. They now had the
common drip oiler down through the water hopper opening. The
redesigned fuel pump was now relocated to a position under the head
and operated by a valve push rod. The fuel fill was relocated from
a tube up the back of the water hopper to a more typical Hercules
shaped spout located at the front of the engine base. A cross
section of this engine is shown at bottom left.
Other brands similar to the 7 and 9 HP UA Thermoil were the Boos
Oil Engine and the Hercules Oil Engine. Their serial numbers fall
in line with that of the Thermoils. From serial number data
collected so far, it would appear that about 1500 of this model
were built. Currently, at least 20 are known to exist.
A February 1, 1929 Hercules wholesale price list shows the 7 and
9 HP Hercules Oil Engine at $237.50 and $332.50 plus shipping.
Included was a plain pulley and a 24 hour oiling system. Such an
engine is shown (bottom left), along with a portion of the price
list (right). They were used primarily in continuous pumping
operations. The UA Thermoils were last shown in the Sears catalog
in the fall of 1925 with the 24 hour oiling system being an
option,. Next, we’ll back up to ‘The Cummins
Connection’.
