Been There, Dunn That

By Staff
1 / 6
Tom Stranko's 4 HP circa-1916 Dunn in its restored glory. 
2 / 6
The engine as found. 
3 / 6
Cracked and bent cylin..nterim bearing to block off the oval hole and steady the shaft.  
4 / 6
 Vertical timer shaft and new offset bearing.  
5 / 6
At A Glance:4 HP Dunn• Built by: Walter E. Dunn Mfg. Co.,• Ogdensburg, N.Y.• Year manufactured: Circa-1916• Type: Water-cooled 4-stroke,• vertical 2-cylinder• Horsepower: 4 at 600 rpm• Bore and stroke: 3-3/4-by-4 inches• Ignition: Battery and coil with timer• Weight: ~145 pounds
6 / 6
First fire, July 2004.

Walter E. Dunn Mfg. Co. built the “Dunn Motor” in Ogdensburg, N.Y. The company was best known for its vertical 4-cycle marine engines, which were made in single-cylinder, 2-cylinder, 3-cylinder and 4-cylinder versions. The company was founded in 1900, and was active until about 1922. This engine, a 2-cylinder, 4 HP vertical inboard engine was built about 1916.


I finished restoring this engine this past summer after about 18 months of work. I came across the engine almost by accident in the course of discussing other engines with a Canadian collector. I acquired the engine in October 2002, and started its restoration the following month. At first the Dunn looked like great restoration material, but then I realized the engine had three pretty serious problems: 1: The base plate (which holds the cylinders away from the crankcase) was cracked and pieces were broken out on one side; 2: The two rear support studs were sheared off at the top; 3: Both bronze connecting rods were bent forward. It seemed to me that a scrapper yanking the engine out of an old boat hull with a chain caused all this damage.

I took the engine apart and started cleaning everything. I took the base plate with the loose pieces set in place to Lord’s Welding Shop in Port Crane, N.Y., who not only welded the pieces back in, but smoothed out the weld and marked and re-drilled the standoff and cylinder bolt holes. This saved me a heck of a lot of work by not having to re-create the original cast iron base in steel plate. Plus, I really wanted the engine to be original.

The Dunn was more of a “motor rebuild” job than the last engine I did. That engine, an Emmons, but really made by the Stanley Co. of Swampscott, Mass., required a lot of turning, milling and welding fabrication, plus I did a wet sand and spray enamel finish.

The timer on my engine is the same style as the 1914 rear-mounted units. I suspect Dunn moved the timer up front and high for ease of adjustment – and to keep it away from water. I had to take a light trueing cut on the pot metal timer base to get a stable area for the phenolic body. Aligning the two contact points after putting new hardened contact balls in place was a trial-and-error job. I finally used a caliper to set them both at equal points.

The Dunn’s lubrication system was a subject of much discussion by the crowd at, a great place for information on vintage marine engines. There are no other operating open crankcase Dunn engines, but we figured splash from the crank and the continuous dripping of oil from the drip oilers down past the cylinder walls and into the crank wells would do the job. This is exactly what happens. It is a very dirty, oil-flinging engine! Even so, it has run about eight hours total so far, and the inside is completely slick with oil. (I used mirrors and lights to look up into the wrist pin and small end area.)

The engine’s first outing was at the Southern Tier Antique Gas and Steam Engine Assn. 30th Annual Show, Aug. 27-29, 2004, which is our local show. The Dunn ran steadily at the show for about six hours, only requiring me to keep the drip oilers full and the gas tank topped off.

The Dunn will be on display at the 31st Annual Southern Tier Show, Aug. 26-28, 2005, Maine, N.Y. For more information, call: (607) 642-8554. Contact engine enthusiast Tom Stranko at:

Gas Engine Magazine
Gas Engine Magazine
Preserving the History of Internal Combustion Engines