New-York tribune., 1909-05-09
SOME POINTS ABOUT BUYING A MOTOR BOAT

plug, being simply device containing two cleo
trodes from one TO the Cther of which the electric
spark leaps. thus causing the explosion In the
piston chamber Of the engine. should not be a
formidable thing. and II IS not If appearances
for anything: but spark plugs have been held
accountable FOR more OF the breakdowns and ag-
gravating delays which have fallen the lot Of
motor boat men than probably any other one piece
Of mechanism entering into the makeup OF a motor
boat.
The spark plug. in It's rudimentary form consists
Of two electrodes contained I'm and yet insulated
from each other by some substance which is
good non-conductor OF electricity. At the inner or
smallest end Of the plug the points Of the cleo
trodes come within about one thirty second of an
inch. or the thickness of dime OF each other.
The electric enters the plug through the
innernost electrode leaping this tiny space to the
point OF the other or outer eectrode, which IS
turn. connected with the other end of the battery.
It IS upon the spark developed when the current
leaps from of these tiny points to the other
that the efficiency OF motor boat engine generally
stands falls.
ono great trouble with spark plugs has been the
substance out of which they made. Various
substances have been tried and being used
with varying degrees of success. The extremely
high voltage TO which the electrodes are subjected
makes it no easy matter to find substance which
will successfully withstand all the attempts of the
current to cut across or leak" from electrode
10 the other in tho interior OF the plug. without
going the ends and making the desired leap from
point to point. which produces the desired spark
Plugs made of mica. Of porcelain. or stone and
other substances and there are many different
makes on the market
Another source of aggravation arising from the
spark plugs is the tendency OF the points OF
the electrodes 10 become covered over with SCOT.
carbon and oil in such manner to form
veritabe bridge. which the current makes the
complete circuit without producing the spark.
Many ingenious devices for preventing the forma-
tIon of this deposit the ends of the electrodes
have been perfected and Il number of them now
working very successfully. There plugs with
electrodes hooded to protect them from the de
poslts OF the explosions; there plugs with cleo
trodes drawn out TO threadlike proportions plugs
with adjustable electrodes, plugs with aIr-cooled
electrodes. and plugs with four electrodes instead
two that if one set goes wrong the other Will
still remain in working order. But whatever style
of plug the engine with which his boat
is equipped, the owner of a motor boat would
do well before starting any kind OF a trip to
see to It that he has with him at least more than
the one plug fitted to his engine.
II his engine works faulty the experienced
motor boat man. having satisfied himself that there
nothing wrong with the carburetor and fuel sup
ply system. turns at once to the examination Of
the spark plugs If they are soOty they are
cleaned. II they broken there is too great
a space between the points of the electrodes they
are thrown aside worthless. If the plug ap-
pears be all right its value determined
by placing it top of the cylinder and then
ing the engine slowly with the electric switch
on II bright blue spark appears 1t is taken as
evidence that the plug is 20. X" and the search
for the trouble is continued in the timer or
mutator. which is examined to determine whether
its contacts perfect and whether igntiOns
taking place in order and at the proper time. If
the trouble is not found there. examination of
the Insulation of the wiring takes place. the coil
and vibrators are tested and If not found at any
Of these points the trouble is finally located in
the batteries which have become depleted. Thus.
although the several parts of the ignition system
of motor boat are of themselves rather perpex-
ing, taken together they form a complete chain.
a certain clew which. followed systematically.
cannot fail to lead one who goes about the search
understandingly to the seat OF any temporary
trouble