Grasser Marine Engine – Part 1 of 2

Despite a missing piston and connecting rod, a circa-1907 Grasser marine engine comes back to life.


| June/July 2016



Grasser 1

Circa-1907 Grasser marine engine

Photo by Dave Irey

Circa-1907 Grasser marine
Manufacturer: Grasser Motor Co., Toledo, OH
Serial no.: None marked on engine
Horsepower: 2-1/2-3 hp (est.)
Bore & stroke: 3-1/16 in x 3-1/4 in
Flywheel dia.: 12 in x 2-5/8 in
Ignition: Spark plug w/battery and buzz coil
Governing: Throttle

In 1995, an acquaintance of mine acquired a 1-cylinder, 2-cycle Grasser marine engine made about 1907 by Grasser Motor Co. in Toledo, Ohio. Very little is known about the company; even C.H. Wendel’s American Gasoline Engines Since 1872 shows Grasser in the index only. I acquired the engine in 2014 and decided to get it running again, but not cosmetically restore it. It’s not rusty or scruffy, and has very good paint on it, possibly the original, and a very heavy-duty looking clutch.

Missing parts

The piston and connecting rod were missing, but I thought I could find a piston from a small engine that would fit. However, it seems very few engines used a 3-1/16-inch piston, and one I did find, the piston was no longer available. A decision was made to carve one out of a round billet of  cast aluminum, which I bought from my local metal supply store, 3-1/2 inches in diameter and 5 inches long. In the July 2005 issue of GEM, the late Glenn Karch wrote a good article about machining an oversize piston to fit a worn cylinder in one of his Hercules Engines. His was a little easier to do as he had a piston to copy from; in my case, I had nothing to go by!

I reread his article and gained some insight into how to set up the lathe and mill. I started by honing out the cylinder so as to get it as smooth and round as possible. This is a headless, dome-top engine, so all the work is done from the bottom end. As a starting point, I mocked up a piston from pine wood, 1/2 inch thick, 3-1/16 inches wide and 3-1/2 inches tall with a 3/4-inch wrist pin hole drilled in it 1-3/4 inches from the top. I glued a 3/4-inch wood dowel into the wood pattern, then using two pieces of a broken wooden yardstick I made a simple pattern to use as a jig for measuring the connecting rod.

The jig has two vertical slots cut in it 3/16 inch wide for making adjustments. The two pieces are held together with a machine screw and nut and washers. This is to get the correct length of the rod when the engine is at bottom-dead-center. In this 2-cycle engine, the intake and exhaust ports are directly across from each other. At bottom-dead-center the piston crown has to be just below the ports for the engine to breathe. I installed the wooden piston pattern in the cylinder bore so the top of it was just below the ports. I looked in the exhaust port with a small flashlight to make sure it was in the right spot and locked it there with a wooden wedge. Next, I installed the crankshaft, positioned at bottom-dead-center, and adjusted the sliding yardstick pattern so it touched the crankshaft journal. I now had the needed connecting rod length, 6-11/16 inches.