A Utilitarian Boat from Japan
by John McGeorge
(Excerpted from The Mariner's Catalog - Volume 3)

Dear Editors:

I was enjoying your Catalog and general wish book and some of the stuff reminded me of a year I spent on Unishima, which is on the north end of the Tsushima chain between Japan and Korea. The island is the top of a sunken mountain range (so is the whole of Japan) and so the area is laced with bays, sounds, harbors, and coves. The natives have some ideas of boat construction which I think might interest the small boatman.

The basic boat is a 15- to 20-foot modified skiff. The interesting part is that the Japanese have solved a number of problems in a most practical manner, and even a real Maine hard-shell might find some virtue in the solutions.
The idea that interested me most is the displacement problem. They have very small semi-diesel engines and limited power. As you can see in the sketch, the hull is divided into an upper and lower section. When you are lightly loaded, you move like a gull. Outside the bay or under a heavy load, the upper hull is in the water and gives you more width for stability. The only disadvantage is a sickening tendency to lay over on her beams when you turn sharply, when lightly loaded in a smooth bay. But once you learn she isn't going over, you feel better.

The Engine

The engine in the boat I was on was a semi-diesel — low speed, one cylinder, and two cycle. The engine started with a gasoline carburetor when it was cold. Otherwise, it would start as a diesel. The gasoline spark was supplied by a Wico magneto, which was operated by a pin on the inside of the flywheel. The spark advance was accomplished by a lever which moved the magneto around the flywheel perimeter. The injection pump and water pump were mounted together and operated by a set of gears from the crankshaft. The cooling water came into the bottom of the block via a brass plunger pump. The injector pump was mounted on the same frame and the speed control was accomplished by a lever which effectively shortened the injector pump stroke. You could see how the cooling was going by watching the water pee out the side of the block into a funnel and down the discharge pipe and over the side.

The engine had a dog clutch and was strictly all-on/all-off. The engine made maybe 150 rpm wide open and so idled at 30 rpm or less. You could watch the flywheel and by diddling the "kill" button, you could make the engine miss a spark and stop and reverse.

The fuel was some kind of diesel oil that looked like it had just been drained from an auto crankcase, it was stored in a two-gallon tank attached to the bulkhead above the engine. Spare fuel was bailed into the tank with a liter can as required. The Japanese who owned our utility boat refused to use G.I. diesel fuel as he claimed it was too good and would spoil the engine.

The lubrication was by a drip oiler which fed oil in at the bottom of the cylinder and about five gallons of #20 in the crankcase. No oil pump, just a sight gauge.

The exhaust stack went straight up through the doghouse roof and was without a muffler. It was a comforting sight to see the sparks fly up at night. Kind of homey-like. The noise was a masterful "thump-thump-thump," kind of like a small boy hitting an empty wooden box with a hunk of pipe.

The starting gasoline was carried in a large oil can and was metered into the float bowl or the carburetor in sparing amounts, just enough to get the business going in the combustion chamber. The combustion chamber had a glowpiug which was a marble-size brass ball located on the inside of the head near the injector inlet. This served to ignite the fuel. The compression ratio was low, I understand maybe Wi to 8:1, not too high for a diesel.

The propeller was a two-bladed one in bronze. The shaft had a universal joint just outboard of the transom, and the supporting strut was constructed so the prop could be lifted up level with the afterdeck.

The Boat

The upper hull overhung the transom by several feet. The hoisted prop was available through a hatch in the deck. This was nice, because you could lift the wheel and clean off the seaweed or clear a fouled line. I also understand you could pull up the propeller to avoid damage when operating in shoal water, providing you kept the rev's down when doing so. The system was most handy.

(click to enlarge)

The rudder was operated by a quadrant and tiller ropes from a double inside-outside wheel on the doghouse. The bottom of the rudder was pivoted and would flip up if it hit an obstruction.

The doghouse was handy, it was windowed so you could steer from inside, though it was crowded with a Japanese, an American, and the engine. Frequently in cold weather, the skipper would stand inside with only his head and shoulders out the top.

The hull was divided by at least three and probably four transverse bulkheads. The foredeck had hatches and the wells were frequently used to hold water and live fish. The upper hull had scuppers which could be closed with wedges and plugs so it was self bailing if you desired. The construction was pine with oak frames and wrought iron fastenings. The life of the boat was 15-20 years, the owners told me.

I sailed about twenty miles south along the west side of Tsushing in one of these boats in a booming gale looking for a drifting mine. Thank God I never saw it. The sea was rolling about 10 feet high and cresting once in awhile, and though I was so scared I couldn't even pray, we never shipped any water and the Japanese waterman that was driving thought it was a jolly trip. I got him drunk that night and we came home the next day when the sea was a little calmer.

I'm a Long Island Sound man and I sure wish I had one of those boats.

—John McGeorge