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