If desired, a double suction may be fitteed to the pump, one branch leading as above and the other leading to the bilge inside. A valve in each branch will allow either to be used as desired. In this way the pump may be used to pump out the boat. As all of this water passes through the cylinder jackets this use of the pump is questioned by many. If, however, the bilges of the boat are kept fairly clean and the pump is used for this purpose only at the beginning of a run the effects cannot be very bad.

The connection from the pump discharge d to the cylinders should be found already piped; in fact, on small engines the pump is attached directly to the cylinder. The outlet 0 from the cylinders may either lead directly overboard through the side of the boat above water, or have a branch b leading into the exhaust pipe. In the latter case a valve should be fitted in each pipe so that the water may flow either overboard or into the exhaust, or both of these ways. The cooling water should not be put into the exhaust until the latter has become heated, and should be taken out from the exhaust a short time before the completion of the run, so that the moisture may all evaporate, leaving the pipe dry.

The piping g for the gasoline supply requires the greatest care as any leak may have fatal consequences. Too much stress cannot be laid on this point as nearly all accidents can be traced to this cause, combined with more or less carelessness. The gasoline tank should be of solid construction of either copper or galvanized iron. It should be well riveted and soldered, and thoroughly tested. The filling pipe should extend from the tank to above the deck, so that any overflow while filling the tank will run overboard instead of into the bottom of the boat.

Many people indorse the fitting of pans or other arrangements to catch and carry off any leakage, but it is, in the writer's opinion, best to make sure- that all joints are absolutely tight, and assure that they stay so by occasional observation. The piping for the gasoline should be of either copper, brass or lead with as few joints as possible and those, except a union at end, soldered. A stopcock should be soldered to the tank and another fitted to the carburettor.

Some form of strainer had best be fitted in the gasoline pipe near the carburettor. Fig. 76 shows a good form of device for this purpose. It consists of a chamber containing a screen of wire gauze, through which the gasoline must pass. The bottom can be unscrewed and any collection removed. A device like this will remove any sediment or water which may be contained in the gasoline. If it is not possible or desirable to buy one, it is possible to make one out of pipe fittings which will answer the purpose. A fitting of this kind is likely to save a great deal of bother some time. The caution should again be repeated, to have all gasoline connections absolutely tight.

The gasoline tank may usually be placed wherever is most convenient. The most common place is perhaps in the bow, as the space there is of comparatively little value. When the engine is near amidships and a water tight standing room is fitted, a very good position is under the standing-room seats. Any possible leakage would then drain overboard. The tank should, of course, be kept as far away as possible from hot exhause pipe or muffler.

This completes the usual piping, and any additional piping would be simply an extension of the piping just described.

The batteries, coils and wiring should be kept in a dry place, as any moisture greatly interferes with their action or may even ruin them completely. If a magneto is us used it may be fastened to the floor or to a frame on the engine. The latter method is preferable when possible, as there is less likelihood of damage.

Fig. 77.

All wiring should be of the best grade of wire, and joints and connections should be carefully wound, or best, soldered, and taped. In the case of a jump spark engine the coil or coils should be placed as near the engine as is convenient, to reduce as much as possible, the length of the secondary wiring.

It is often advised to seal up the batteries in a tight box, or even bury them completely in tar or other material, with the object of keeping the moisture away from them. These methods are, however, hardly to be advised, as a single poor cell will spoil the action of a whole set, and it is better to have the cells accessible, so that in case of trouble they can be tested and the poor ones replaced. Two sets of batteries should always be used for general running with an occasional rest, and the other set retained in their full strength for starting or for emergencies.

In all the piping and wiring a great effort should be made to keep everything as simple and direct as possible, so that in the case of trouble or repairs, all parts may be quickly and easily gotten at.

It is also important that a convenient tool and supply locker should be provided. It is too often the case that small tools or parts which should be on hand are missing, causing much delay and inconvenience. This locker should be handy of access, and should be of such construction as to prevent the access of water to the tools, which quickly renders them useless. This is a point to which too little attention is usually given.

It is, of course, impossible to enumerate all of the small details of the work of instalation, but with the principles of the above in mind, no difficulty should be found in following out the work of almost any ordinary installation.