Stover Engines: The Cooper-Stover Junior Range

Unraveling the history of Stover engines "Down Under."

1922 Cooper-badged 3 HP tank-cooled Stover Type W

George Best's 1922 Cooper-badged 3 HP tank-cooled Stover Type W.

Photo by Ron Wiley

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I first became interested in old stationary engines around 1998, when I was given what turned out to be a 1920 3 HP Cooper tank-cooled Type W. It was built by Stover Mfg. & Engine Co., Freeport, Illinois, and supplied to Chicago Flexible Shaft Co., Chicago, Illinois, for export to Cooper Engineering Co., Sydney, Australia. It is from the Stover Junior Range of horizontal, open crank engines produced from 1910 to 1923, and it is found in Australia as either a hopper- or tank-cooled engine.

What made me look more closely at this engine was an e-mail in July 2012 from Joe Maurer in regard to tank-cooled Type Ws in the Stover ledger records. He mentioned this in his column in the August/September 2011 Gas Engine Magazine, in which he said the following:

“A recent request from Tim Clancy of Orange, New South Wales, Australia, to look up his Stover no. W112529 started an interesting chain of events. Tim’s engine is hopper-cooled. He casually mentioned that his mate, Rod Schoonderbeek, had Stover no. W127245 that was tank-cooled. I had never heard of a 3 HP tank-cooled Type W, but the records confirmed it. There were at least three groups of Type W 3 HP tank-cooled engines, all sent to Chicago Flexible Shaft Co.”

Stover publications

I started with a look at the Stover range of Junior engines, from 2-1/5 HP to 14 HP. This information comes from a repair price list for Stover horizontal hopper-cooled engines dated effective July 1, 1925. There is no mention of the Junior Range, but I was able to confirm from C. H. Wendel’s Power in the Past Vol. 3 that the engines listed below are from this range:
Prefix W: 2-1/5 HP & 3 HP. The 2-1/5 HP was first produced on Nov. 15, 1910, and rerated to 3 HP in September 1915 by increasing the rated speed from 375 RPM to 500 RPM.
Prefix T: 4 HP and 5 HP. The 4 HP was first produced on July 26, 1910. I have no information as to when this engine was rerated to 5 HP. Were the last ones shipped to Australia in 1923 5 HP engines?
Prefix RX: 6 HP. This looks to have been released in December 1915 to replace the rerated Type X.
Prefix X: 6 HP and 8 HP. It was released as a 6 HP engine on Dec. 5, 1911, and rerated to 8 HP in December 1915.

I have not found any information on the three following engines:
Prefix U: 10 HP
Prefix RH: 12 HP
Prefix RF: 14 HP.

Of note is that the above referenced Stover publication only mentions hopper-cooled engines in the Junior Range.

The Cooper register

The register covers all engines sold by Cooper’s from 1902 to the late 1960s. Cooper-badged Stovers date between 1910 and 1947. Of the 3 HP Type W, I have 16 tank-cooled engines in the Cooper register plus seven hopper-cooled and five unknown for a total of 29 engines. I have only three 4 HP Type T engines on the register, and serial no. 90316 from 1917 is a hopper-cooled, throttle-governed engine. There are two 6 HP Type RX tank-cooled engines on the register. The larger engine appears to be very rare.

My tank-cooled Type W is fitted with a Wico EK high-tension magneto. An old gentleman who started as a 15-year-old at Cooper’s Melbourne, Australia, workshop in 1927 told me that any pre-1925 Cooper/Stover that came in for repair had a factory Wico conversion kit fitted. The igniter and Webster Tri-Polar was thrown in the bin; the bracket to mount the Wico has Stover part numbers cast on it.

Cooper publications

I looked at two Cooper publications I have from around 1918-1920. The first one, Publication No. 47, is the instruction and parts book for throttle-governed 3, 4, 8, 10 and 12 HP kerosene engines. The second one, Publication No. 48, is the instruction and parts book for hit-and-miss 3, 4, 8, 10 and 12 HP gas engines. No prefix letters are given for these engines.

I knew the Type W and Type T engines could have a tank- or hopper-cooled cylinder. On the smaller engines (3 and 4 HP) the cylinder bolts to a vertical flange on the main engine casting and is held in place with 4 bolts. The larger engines have horizontal flanges on either side of the cylinder and are bolted to the frame with three bolts per side.

Until recently, I was under the impression that the three larger engines were only available as tank-cooled engines. The operating instructions in the Cooper publication are numbered, and “Instruction No. 31” says: “If the engine is hopper-cooled type, no water connections and tanks are used. If it is a tank-cooled engine, the cylinder is cooled by means of a water-circulating tank.”

I also have a poor copy of Cooper Publication No. 51 for horizontal petrol engines (Type W). The picture on the front cover shows what looks to be a throttle-governed, hopper-cooled Type W (i.e., a gasoline/kerosene engine). “Instruction No. 31” is the same as in the other two Cooper publications.

There are two parts lists in the back of the book for the 3 and 4 HP engines. Part No. W400 is the cylinder, but it does not differentiate between the tank- and hopper-cooled types. For the 8, 10 and 12 HP engines, Part No. 1 is the cylinder, but again it does not differentiate between the tank- and hopper-cooled types.

Publication No. 51 is confusing because the 4 HP has “Type T” stamped on its plate. Two 6 HP Type RX engines exist in Australia, but there is no mention of this engine in any of the Cooper Publications.

This indicates that five different Junior engines sold by Cooper’s could be supplied with hopper- or tank-cooling, and possibly six engines with the 6 HP type RX. No 8, 10 or 12 HP engine have come to light so far.

You could have a hit-and-miss gas engine or a throttle-governed gas/kerosene engine. There are two types of carburetors and linkage used for throttle-governed engines depending on if they were hopper- or tank-cooled. This range was a real mix-and-match when it came to choosing the engine you required.

At the time I got the e-mail from Joe, I also got one from George Best, who lives near Beaverton, Oregon. George had purchased a 1922 Cooper tank-cooled Type W from Australia. George made the comment that when he received his copy of the August/September 2011 issue of GEM, he agreed that “those tank-cooled Ws are pretty nice. Wouldn’t mind adding one of those to my collection, it would look good with my other tank cooled Stovers.”

George also said: “One thing I’ve noticed about the engine I have is that the serial number is also stamped on the crankshaft keyway. Maybe you could ask other Cooper/Stover owners to check and see if that was a common practice or is mine an odd-ball with the serial number stamped on the engine?” I have checked my engine and the serial number is not stamped in the keyway.

Starting from late 1917, any Stover engines shipped to the Chicago Flexible Shaft Co. could have had the following plates: Cooper Engineering – Australia; Wm Cooper & Nephews – New Zealand; Cooper Stewart Engineering – Argentina and Uruguay (a couple engines with this type of plate have found their way to Australia); Cooper Stewart Engineering – UK (I have no information regarding engines sold by this company); Stewart – USA & Canada.


I was aware hopper- or tank-cooled engines in the Junior Range were available in Australia, but until Joe came across a tank-cooled Type W that he did not know existed we had an interesting situation. Five engines from the Stover Junior Range were sold in Australia and New Zealand between 1917 and 1923 as either hopper- or tank-cooled. This must have been done at Cooper’s request, but why? That’s the $64,000 question.

Just to put the cat among the pigeons, I was recently told about a 1930 3 HP enclosed-crankcase Type TC that now resides in the Netherlands, but was obtained from Uruguay. I know very little about Cooper Stewart Engineering in Argentina and Uruguay, but I now wonder if tank-cooled Junior engines were also sold there.

Contact Cooper-Stover engine enthusiast Ron Wiley via email at