Antique Marine Engine Tips

Basic maintenance and operation tips for antique marine engines.


| May/June 2000



Monarch marine check valve

Monarch marine check valve.

Antique marine engines are different from the typical two flywheel farm engine one sees at shows all over the country. They are different not only in appearance but also in their operation and adjustment of their moving parts. This is even more so in the two-cycle as distinct from the four-cycle gasoline marine engines.

Before discussing adjustments etc., a few important operational differences should be brought out. In this discussion I am limiting my comments to the early turn-of-the-century small boat engines, the so-called 'one and two lungers.' Not that these remarks won't apply in some cases to the three and four cylinder engines of the pre-WWI and later era. In many cases those engines tended to be derivatives of automobile engines rather than designed from the ground up for marine propulsion.

1. These marine engines had two basic speeds: Idle and Full Speed. The maker controlled the top RPM by the size of the propeller. Due to the limited power available and the design and construction of the hull, the boat was 'pushed' through the water rather than riding on top of the water as with today's so-called planing hull. These two basic facts, available power and hull design, meant that the size of the propeller had to be as large as possible to move the boat in the water against the wind and tide or river current efficiently. The propeller in effect becomes a water pump 'pushing' a stream of water. The 'push' is transmitted to the hull through the rotating propeller shaft pushing against the thrust bearing on the aft end of the engine crankshaft. In turn the thrust bearing transmits the pushing to the engine crankcase, and in turn the crankcase transmits the pushing to the engine bed which is attached to the hull.

2. The size of the propeller served as a limit control or governor on the upper engine r.p.m. Typical r.p.m. speeds for the low speed heavy duty engines used by the watermen in hulls up to about 30-40 feet were in the 300-600 range. The typical pleasure launch of 12 to 20 feet would operate in the 500-700 range, even up to 1000 r.p.m. in some cases. In the earliest years the pleasure launches used the same engines as the watermen. It should be noted up until WW II the propeller r.p.m. for the many pleasure boats remained under 1000 r.p.m., even though their engines may have been operating in the 2000-3000 r.p.m. region. This created a need for a reduction gear between the engine and the propeller shaft or a reduction in propeller size which resulted in less than optimum performance at low engine r.p.m. Approximately 700 r.p.m. was a common propeller shaft speed for many pre-WW II pleasure boats up to 50 feet, and many of these hulls had the classic low r.p.m. engines of the watermen rather than converted high r.p.m. automobile engines. The typical small boat marine engine needed no governor for most operations, so none was provided. There was one operational condition for which one often wished they had a governor and that was when, in heavy swells, the propeller would come out of the water and the engine would tend to race. In 1901 Ray Palmer of Palmer Bros, in Cos Cob, Connecticut, took out a patent on an inertial governor. His patent extended the M/B ignitor trip arm and added an adjustable weight that allowed one to set the rate of ignitor tripping. How successful it was I don't know, and I have never seen any Palmer ad or engine for that matter that had such an ignitor tripper. In the larger engines used on tug boats and big yachts, governors were provided in many cases. When running an antique marine engine without a load one must be careful not to let it over speed, as they can quickly get out of control with possibly deadly results. The typical hit/miss farm engine operating under no load, unlike the marine engine, is controlled by the governor.

4. Essentially all the successful early small boat marine engines mass produced were two-cycle, two-port. The two-cycle, three-port didn't become popular until the Joseph Day, UK patents ran out in the 1906-07 time-frame. A few makers bought licenses, but by that time there were hundreds of two-cycle, two-port engine makers that didn't. It seems as though every little machine shop or foundry was making marine engines if they had a local body of water of sufficient size to warrant tooling up. It is said with a probable ring of truth that the reason Detroit became the automotive production center was that most of the early car makers were using small marine engines in their cars. There were a number of marine engine makers in the Detroit area, and the hollow castings a marine engine water jacket required was a whole new art-form for most foundrymen. It was only natural the marine engine makers by 1905 were switching to making water-cooled automotive engine designs that overcame the speed/weight limitations of the classic two-cycle two-port marine engine.

By 1905 the basic design of the two-cycle two-port was so well imbedded in mass produced marine engines that there were very few changes in the next thirty-plus years. A few makers' designs even lasted in production up until the 1970-90 frame.