main trouble is caused by particles lodging in the valves and the rapping will in most cases jar them free.

If this is ineffective, the trouble may be with the screen at the inlet on the bottom of the boat. In this case, reach over the side and scrape the screen, using a long stick. If out of reach with a stick, back the boat and throw the obstruction off. Another way is to pass a rope under the boat, and, holding both ends, seesaw it across the screen.

Should the screen be clear, see if there is dirt in either valve. The next place an obstruction can lodge is in the small pipes where the water enters the water-jacket. Often these are provided with ground joints held together by means of a bolt passing from bottom to top through the interior. This makes the available passage very small and weeds can lodge in it. The bolt holding the joint together is frequently made of steel or iron and rusts quickly; brass or bronze bolts should be used.

The interior between the water-jacket and the cylinder will in time corrode and the sediment clog the water circulation, particularly at the outlet on the outlet side of the cylinder. The sediment from this cause and from scaling should be cleaned out every season. The exhaust pipes are usually iron, which scale badly after a few years and should be replaced. The muffler also is constantly scaling when it once begins and will choke the exit of water and gases.

83. Between the engine and the connection with the inlet for the water circulation there should be a short length of rubber pipe to take up the vibration. Another piece of rubber pipe must be between the engine and the pump. After long standing the pump and pipes may be entirely dry. It is well then to take off the head-nut and pour in a few drops of oil; also, a liberal supply of water to fill the pipes and help the plunger to start the supply should be poured in. It usually takes a minute. or more to send the water out of the exhaust, as the whole waterjacket must be filled before that can happen.

When running in a seaway that will lift the sides or ends of the boat clear of the water, the intake may be lifted out and the continuity of the flow be broken. This condition will be

made known by the different sound that will come from the exhaust. This will cause no harm, as there is always water enough in the pipes and jackets to do all the cooling necessary.

84. The water-jacket sometimes becomes so corroded that it will leak. Temporary repairs can be made by stopping the engine and letting the water go below the level of the leak, and then drying off the surface and binding it with bicycle repair tape. A liberal use of the drainage cock will get rid of much sediment.

After there has been trouble by heating from lack of water do not turn any water into the jacket until the cylinder has become cooled. The cold water is apt to crack the hot metal.

A fair percentage of water should be allowed to go through the muffler to keep it from overheating. In cold weather, make it a rule to open the drainage cock at the end of every run. It will keep the pipes or jacket from bursting.

85. After taking off the cylinder head a few times without renewing the gasket, water may appear in the cylinder, and be found on the sparking points. The presence of water in such intense heat creates a vapor that dilutes the gasoline vapor until it is useless. When any considerable quantity of water is found to be in the cylinders take off the heads and examine the gasket. The probability is that it needs renewing.

When water appears in the bottom of the boat of a higher temperature than the surrounding sea the exhaust will be found leaking in some part. Any unaccountable leak in the boat may be looked for around the water intake as it enters the hull. Between the part attached to the bottom of the boat and the pipe connected to it, there is a nipple; this nipple may loosen through vibration and shake out the lead packing. For this trouble wrap the joint with a closely woven cloth smeared with grease, and lash it firmly and thickly with fine twine.

TOOLS AND NECESSARIES

86. A few tools are always necessary in running a marine gas engine to get at or remove parts that may have to be taken down for adjustment, repair, or inspection. The following is a list of tools that will be found useful for this purpose:

MANAGEMENT OF MARINE
GASOLINE ENGINES

(PART 2)

TROUBLES AND REMEDIES

MARINE ENGINE TROUBLES

LEAKY CYLINDERS

1. Testing the Compression. One source of trouble in a marine gasoline engine is loss of compression in one or all of the cylinders, which may be due to any one of a variety of causes and results in a loss of power or perhaps in a failure to start the engine. An easy method to test the compression in the cylinder of an engine, is to try them, one at a time, in the following manner:

Close the petcock and holding the piston at the top of its stroke for about minute let it go suddenly; if it does not bound back the cylinder leaks and must be examined. To make sure try again and see if the piston will go by the center with a little extra exertion. Then try it by holding the piston for 1 minute. If the piston slides by with almost no extra effort it should be attended to if good results are desired. Try each cylinder separately, keeping the cocks open on the others.

In the case of open-base engines, lack of compression will make itself known by black smoke issuing from the crank-case.

2. Lack of compression is a trouble that seldom comes suddenly, and has probably been making itself manifest for

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