English Instruction Book "A" August 1928
Copyright © Kelvin Diesels PLC


The Running and Repairing of

Models A2 & A4

1. IN drawing up this Instruction Book we have made it more comprehensive than is usual in order that our customers may themselves understand and maintain their engines. Any advice which we can give by letter is at your service, whether you are the original purchaser of the engine or not. When writing to us do not omit to quote the number of the engine stamped on the crankcase. If you have occasion to return any part, label it with your name and advise us of its despatch.

2. REPLACEMENTS.—An illustrated price list of KELVIN spare parts is contained in each tool box. All parts ordered should be described in the terms of this list. The engine number should be quoted. If you have no ledger account please remit cash with order. If you cannot arrive at the exact amount remit an approximate sum. If you are able to fix the part of the engine yourself, order it from us direct. If you cannot fix it yourself, order it from our local agent, or if we have none, from anyone competent to fix it for you. Boxes containing a selection of engine spares to suit each model can be supplied, and are recommended for customers in outlying districts. The contents and the price of these " Spare Boxes" is indicated in our spares list.

3. TOOL BOXES.—A box of tools accompanies each engine. It is closed with a lead seal, and should be delivered to the customer with the seal intact.

4. PARAFFIN.—We are frequently asked which is the best brand of oil for use in a paraffin engine. The question is difficult to answer because—both makers and merchants are giving to selling different oils under the same brand, and the same oil in different localities, under different brands. Generally speaking, Russian oil is the best, but all Russian oil is not alike. Good oil is also produced in Scotland. American oil is unsuitable. Users in the United Kingdom are advised to write to the under mentioned asking which of their brands is most suitable for a "Kelvin" engine, and the name of their nearest authorized agent. Users abroad are advised to try all available brands and select the one which works with least tendency to knock.

Shell Mex Ltd., Shell Corner, Kingsway, London, W.C. 2
Anglo-Persian Oil Co., Ltd, Gt. Winchester St., London, E.G. 2
The Pinkston Oil Co., Mid Wharf, Port Dundas, Glasgow
The Merchant Trading Co., 34 Bishopsgate Street, London, E.G.
The Scottish Oil Agency, Ltd., 53 Bothwell Street, Glasgow.

5. LUBRICATING OIL—Lubrication is the most important care of an oil engine. Use good oil such as is sold for motor cars, and see that it is delivered to you with the Maker's seal intact- We cannot enumerate all the Brands that are suitable, but we ourselves use the following :—


Prices Patent Candle Co., Ltd., Belmont Works, Battersea, London, S.E.


C. C. Wakefield& Co.. Ltd., Cheapside. London E.C.2.


Shell Mex Ltd. Shell Corner, Kingsway, London, S.W.1


Vacuum oil Co., Ltd., Caxton House, Westminster, London, S.W.1.

All authority to sell oil under our registered mark KELV0L has been withdrawn.

6. THE LUBRICATOR should be filled with oil (par. 5) and replenished when empty. The knob should be pressed down once per hour of running. If the running has been at reduced speed, the knob should be depressed only to a limited extent. The base of the lubricator contains a piston, which forces the oil into the crankcase. A spring raises the piston after it has been depressed. A collar on the stem limits the travel of the piston, which should be as follows :—

Model A4, running up to
r.p.m., travel 3 1/2"
Model A4, running up to
r.p.m., travel 2 15/16"
Model A4, running up to
r.p.m., travel 2 5/16"
Model A2, running up to
r.p.m., travel 1 3/4"
Model A2, running up to
r.p.m., travel 1 7/16"
Model A2, running up to
r.p.m., travel 1 3/16"

7. ENGINE INCLINED.—An Engine stopped at any time should contain in each division of the crankcase sufficient oil to reach the point of the crankpin bolt- The sloping oil ducts visible within the crankcase keep the oil constantly circulating from the rear to the front, ensuring that the forward piston gets its share, even although the engine may be inclined to the extent of 1 inch in 9. As the engine must not be worked at a greater inclination than 1 in 9, it is advisable to measure the inclination when the boat is at full speed. This may be done either with a spirit level laid on some part of the engine, or with a plumb line held in front of the flywheel.

8. BEFORE STARTING A NEW ENGINE.—Work the pumps by hand until water issues from the exhaust pipe. See that the crankcase contains sufficient oil (par. 5) to reach the split pin of each crank when in its lowest position. Fill the lubricator with oil. Put into the reverse gear case the quantity of oil mentioned on the instruction plate- Oil the minor parts — lower starting wheel and pawls, governor, governor lever, chains.

Detach the stopping wire.
Turn on petrol at tank, float chamber, and pilot cock-Prime manifold, retard ignition (lower lever down).
Completely close throttle (upper lever up).
Put reverse gear at neutral (knob on wheel down).
Turn starting handle.
When engine starts advance spark half way, put in clutch, and open throttle gradually.
If engine threatens to stop, promptly close throttle and keep engine running slowly until it has warmed up a little.
See that pumps are working.
See that all cylinders are firing by listening to exhaust.
The spark should only be fully advanced when the engine is running at full speed.

Detach the stopping wire,
Drain float chamber of paraffin with pilot cock open.
Close drain cock, open pilot cock and turn petrol into float chamber.
Prime manifold, retard ignition (lower lever down).
Completely close throttle (upper lever up).
Put reverse gear at neutral (knob on wheel down).
Turn starting handle.
When engine starts advance spark half way, put in clutch and open throttle gradually.
When engine is thoroughly heated (4 minutes at full speed for Model A4, 3 minutes for A2) turn float chamber cock from petrol to paraffin.
If engine spits fire at air inlet it is not sufficiently hot to consume paraffin. Before leaving engine see that all cylinders are firing by listening to exhaust. Spark should only be fully advanced when running at full speed- When engine is thoroughly hot pilot cock should be closed,' but must be opened again before engine is required to run slow.

11. TO STOP THE ENGINE.—Shut off fuel and allow engine to drain float chamber. To stop engine suddenly close throttle and pilot cock. A paraffin engine should be turned on to petrol before being stopped.

12. SLOW RUNNING,—An engine must be thoroughly heated before being run slow on paraffin. See that all cylinders are firing by listening to exhaust. If any cylinder is missing, some of its paraffin is passing into crankcase- Turn engine on to petrol until missing ceases. Slow running should be done with spark at half travel. When speeding up on paraffin, open throttle gradually.


Causes :—
(a) lack of petrol—see that there is a flow at drain cock ;
(b) paraffin remaining in pilot—drain the copper pipe ;
(c) air leak in pipe connecting pilot with float chamber— tighten coupling nuts;
(d) throttle valve not completely closed (pars. 32 and 33);
(e) over primed—turn engine with priming cock open and pilot cock closed.

14. ENGINE SPITS FIRE AT AIR INLET.—A paraffin engine does this if turned on to paraffin too soon. Other causes:—(a) air lock in pipes—blow into tank; (b) stoppage of spray jets; (c) stoppage of filter.


(a) over primed— turn engine with priming cock open and pilot cock closed;
(b) poor petrol—heat sparking plugs;
(c) lack of spark— test plugs (par. 20);
(d) magneto contact breaker stuck—remove small cover (par. 25);
(e) magneto wrongly set—see instruction plate;
(f) sleeve driving mechanism wrongly set—turn engine till the hole in No. 1 sleeve appears in centre of " peep" hole, see that No. 1 crank is up and mark on flywheel exactly central—repeat operation for each cylinder in the following rotation; 1, 2, 4, 3 for 4 cyl. engines, 1, 2, 0, 0 for 2 cyl. engines;
(g) sleeve mechanism damaged—examine it and see (pars. 43 and 44).


Causes :—
(a) sparking plugs missing-ascertain which by observing which is coolest (par. 22);
(b) lack of fuel—see that there is a full flow at the float chamber drain cock ;
(c) air lock in pipe line due to tanks being run empty—blow into tank;
(d) water in fuel—open drain cocks of tank and float chamber;
(e) choked spray jet—accessible by removing screw plug.

17. IF THE ENGINE STOPS TIGHT, feel immediately all the bearings of the crankshaft, sleeve driving mechanism and reversing gear to ascertain which has caused the stoppage. If none are more than hand hot the stoppage must be due to some other cause (a) lack of lubricating oil (par. 1), (b) sleeve tightness (par. 18).

18. ENGINE BECOMES TIGHT AFTER STANDING.— This may be due to the presence of water about the sleeves. If the slackness in the sleeve chains cannot be pulled by hand from side to side the sleeves have become tight—pour paraffin into the cylinders, and by the flywheel gently move the engine in both directions. The cause of the water must be found at once or the engine may become ruined. Examine the exhaust manifold joint (par. 62).

19. ENGINE KNOCKING—If knock is within crankcase. look for something loose, misplaced, or running hot. If knock is within cylinder, and only when running at full speed, it may be due to (a) the quality of the fuel—try another brand (par. 4), (b) excessive soot within cylinders—remove water covers (par. 48), clean cylinders one at a time (par. 47); before starting see that you have the necessary joints ; (c) too heavy a propeller may cause an engine to knock (par 65); (d) slackness at the sleeve balls ; (e) in a 4 cylinder engine slackness at the middle bearing causes a knock (par. 51).

19a. ENGINE LOSING SPEED.—If the loss is gradual it may be due to an accumulation of soot and salt in the silencer—clean it out—or to the fouling of the vessel below water. A growth not visible to the eye is sufficient to affect the speed. If the bottom is slippery to the hand the boat requires cleaning. It pays to use anti-fouling paint, as the best qualities (all brown in colour) resist growth in a temperate climate for four months—more than twice as long as ordinary paint. There are various makes, but a good brand is obtainable from the International Paint & Composition Company, Ltd., 31 Grosvenor Place, London, S.W.I.

20. SPARKING PLUG TEST.—take out plug, lay it on engine so that its body alone makes contact, turn engine by hand. If no spark results (par. 23).

* 20a. ENGINE REFUSES TO TAKE PARAFFIN-—Should the engine gradually take longer to heat up, the vaporizer requires cleaning, spread a crumpled newspaper below the vaporizer, remove the soot door and clean the interior of the vaporizer with a tooth or bottle-brush.

21. SPARKING PLUG, CARE OF—Porcelain plugs must be handled with care. A heavy spanner carelessly applied may produce in the porcelain an invisible crack which in time holds moisture and causes the plug to "short." The thread of the sparking plug should be oiled.

22. SPARKING PLUG MISSING.—If due to soot bridging the gap, it may be cured without stopping the engine by prizing (with a piece of dry wood) the terminal off the plug and holding it (by the cable) at some distance from the plug. The long spark thus produced intensifies the electric current, If missing is due to soot within the body of the plug, take it to pieces. If due to causes described in par. 21. throw it away.

23. SPARKING PLUG ADJUSTMENT.—The spark gap becomes wider with use, and the points should be bent to maintain the gap at '5 m/m or '020 inch (gauge attached to magneto spanner). The size of the spark is in proportion to the width of the gap. A spark too small may fail to start the engine, but a gap too wide may fail to produce a spark. A plug which sparks in the open air may not do so when exposed to the pressure within the cylinder. If the magneto is suspected of being weak keep the gap of the sparking plugs rather close—a small spark is better than no spark.

24. MAGNETO, CARE OF.—Magnetos have ball bearings and require only a few drops of oil once a month. Excessive oil is harmful.

25. MAGNETO CONTACT BREAKER.—The moving arm is liable to become stuck in damp climates owing to the swelling of its fibre bush. Remove the arm, polish and oil the pin; scrape out the fibre bush with the square tail of a small file or other suitable instrument. The fibre pad on the end of the arm should be oiled, but no oil must reach the platinum contacts.

26. MAGNETO CONTACT BREAKER CAP.—The contact points are platinum tipped and gradually wear further apart, with the result that the gap increases. A gauge is attached to the magneto spanner; try it in the gap, and, if necessary, adjust the screw.

27. MAGNETO DISTRIBUTOR.—Some distributors have carbon brushes,, which wear. The dust produced must be removed from time to time. When the brushes wear down they should be renewed; the stretching of the spring serves temporarily.

28. MAGNETO REPLACEMENTS—Owing to the great variety of magnetos which we have been obliged to supply, we cannot keep stock of all magneto replacements, and buyers are advised to communicate direct with the magneto maker, taking care to quote the number of the magneto if it bears one. A magneto sent to the maker should be labeled with the owner's name and its despatch advised to the maker.

J.A. Stevens Limited,
21 Upper Rathbone Place,
London, W.1.
Simms Motor Units Ltd.,
Percy Buildings,
Gresse Street,
London, W.1.

29. THE FUEL SYSTEM.—The fuel flows from the tank to the float chamber, thence to the spraying jets located in a passage leading to the cylinder. Through this passage air is sucked by the engine. That part of the air passage in which the jets are located is restricted in size and is called the choke. The velocity of- the air in the choke is sufficiently high to cause the jets to spray and impregnate the air with fuel Petrol sprayed in an air current evaporates and produces gas ; paraffin requires the addition of heat. In a paraffin engine that part of the air passage where the spraying takes place is heated by exhaust gas and is called the vaporizer. The float chamber controls the level of the fuel a little below the top of the spray jet. Therefore no overflow from the spray jet takes place when the engine is stopped.

30. THE FLOAT CHAMBER should control the fuel level a little below the spray jets, and should be adjusted level.

31. SPRAY JETS are all tested, and the number represents the actual flow through the jet. Never tamper with the orifice. If you wish to experiment, get some spare jets from us.

32. THE THROTTLE VALVE controls only the main supply of gas to the engine. The "pilot" has no throttle valve, and is just large enough to keep the engine running slowly when the throttle valve is closed (upper lever up).

33. THROTTLE VALVE ADJUSTMENT.—Detach the control rod from the throttle lever. Slacken screw in throttle lever so that lever may just be pulled around on spindle. Hold throttle valve in closed position (slot in stem fore and aft) by means of screw-driver Pull lever full back. Re-connect control rod. Pull governor spindle hard out. Bind throttle lever to spindle, If correctly done there will be no play on throttle lever when governor stem is fully extended from governor case.

34. CYLINDERS RUNNING HOT.—Pumps are so designed that cylinders run hottest at low speed.

35. WATER PUMP LEAKING.—If water drips from stem slacken lock nut and gently screw up packing ferrule, not neglecting to re tighten lock nut.

36. WATER PUMP NOT WORKING.—(a) If the pump cannot be worked by hand there is probably seaweed on the strainer outside—detach pipe from pump and blow through it; (b) If due to over tightening of packing ferrule remove pump, pick out packing and replace more loosely. In replacing the pump driving shaft see that jaw actually engages ball on sleeve.

37. THE PUMP STRAINER keeps clear when the boat is under way, but becomes readily fouled if the engine is run with the boat at rest in shallow water. In deep water all seaweed is either on the surface or at the bottom—in shallow water it rises from the bottom.

38. TIMING.—In each sleeve there is a small hole, When that hole appears in the centre of the "peep" hole (starboard side of cylinder) that sleeve is in the firing position, and its crank should be up. Having shipped the chain over the upper sprocket wheel (par. 40), get the sleeve hole into the centre of the "peep" hole, bring the crank belonging to that sleeve to the top (mark on flywheel central), join lip the chain. In a 2-cyl. engine use No. 1 sleeve; in a 4-cyl. engine use Nos. 1 and 4.

39. CHAIN JOINING LINK.—Each chain has a joining link secured by a spring plate. See that the spring plate is properly in position, and carry a spare spring plate, as they are very easily lost in handling.

40. SLEEVE CHAINS (ASSEMBLING).—To get the chain over the sprocket wheel without removing the cylinder, attach the end of the chain to the rim of the wheel, then give the wheel one turn from you. A hole will be found in the rim of the wheel into which the pin of the end link may be inserted.

41. THE SLEEVES in an engine are of two varieties. Each sleeve is numbered at the "peep" hole to indicate the cylinders for which it is suitable.

42. THE SLEEVE BALLS.—Should these become badly worn they can be taken off and renewed. The clenching of the bolt must be done with care.

43. THE SLEEVE BANDS.—Should a sleeve become stuck with rust, the band may rotate on the sleeve and shear the small pins driven through the centre of the balls. If this has taken place the marks on the underside of the band and sleeve will no longer register. To remove the band from the sleeve, first set the sleeve on its end on the bench and hold by means of a long bolt through sleeve and bench. As a new band compresses the sleeve to some extent, see that the piston has adequate clearance at the lower end of the sleeve.

44. THE DISC is the rotating part which drives the sleeves. Both discs in a 4-cyl. engine are alike. Assemble them with the markings forward. The numbers indicate which balls can be put into which holes. In fitting a new disc see that the six pins slide freely into the chain sprocket wheel.

45. DISC BEARINGS.—Should the white metal linings be run out, fit replacements or send the old bearings to be relined. In assembling a new pair of disc bearings, see that the disc (without the sleeves) revolves quite freely in the bearings when the bolts are tight. See also that no part of the sleeves or bands fouls the new bearings. If correctly-fitted, the new bearings will show no warmth after running 5 minutes.

46. THE CYLINDER PORTS.—Each cylinder has two inlet ports on the port side, and two exhaust ports on the starboard side. In addition there is a small inlet port (pilot) on the starboard side, Each sleeve has two inlet and two exhaust ports. The pilot port in the cylinder being opened by one of the exhaust ports in the sleeve after having performed its exhaust service.

47. THE CYLINDER HEAD JOINT is of asbestos paper and perishes each time the head is removed—carry a stock of joints. Do not remove the cylinder heads unnecessarily and replace them with care as they are a close fit in the sleeves. To keep water out of the cap nuts treat the threads with oil paint and put a fibre washer below each nut.

48 THE WATER COVER.—Drain the cylinders of water before removing the water cover.

49. PISTON RINGS.—If good lubricating oil is used the rings never require cleaning. If a ring becomes stuck in its groove ease it with paraffin, if possible without removing it —a ring prized out of the piston is sprung and no longer -gas-tight. Piston rings should be handled with care. Their condition indicates the quality of the lubricating oil in use.

50. THE PISTONS should be renewed when the gauge attached to the sparking plug spanner can be inserted beside a new ring in the upper groove. The piston may be removed in 3 ways — by taking off the cylinders; by taking off the cylinder heads ; by the inspection door. The latter method is the best. Turn the engine until the sleeve is at its highest point, detach the big end and the piston will come down and out by the inspection door.

51. THE CRANKSHAFT runs in suspended bearings lined with loose white metal bushes—easily adjusted—all bushes alike. The bushes should run a year without attention. To tighten a bush "strip" (file) the flat flange of the lower half until the tightening of the bolts binds the shaft, then scrape the inside of the lower half until the bolts can be thoroughly tightened without binding the shaft. The upper half must not be scraped, interchanged, or replaced, without checking the whole alignment of the shaft, which can only be properly done with the crankcase up-side-down, but the upper halves should develop no wear. A little red lead and oil applied to the crankshaft shows up the parts in the bush which require the scraping. When all six bolts are thoroughly tight the crank should be sufficiently free to be turned by one hand applied to the taper end. A white metal bearing properly fitted runs cool from the start. If it shows warmth within 5 minutes it will probably become tighter when running.

52. THE BIG END of the connecting rod is fitted with loose white metal bushes. The adjustment of a bush should be carried out with the other connecting rods detached and pushed up to clear the revolving crank. To tighten the bush "strip" (file) the flat flange until the tightening of the bolts binds the shaft, then scrape the inside of the lower half until the bolts can be thoroughly tightened without binding the shaft. A little red lead and oil applied to the crankpin shows up the parts in the bush which require the scraping. A white metal bearing properly fitted will run cool from the start. If it shows warmth within 5 minutes it will probably become tighter when running.

53. CRANKCASE should be cleaned out once for every 50 hours of running. If this is neglected grit and burnt oil accumulate and destroy the bearings. Any evidence of water such as rust on the bright parts should be investigated at once.

54. OIL LEAKAGE from any part of the engine may result in lack of lubrication and should be investigated at once-

55. REVERSING GEAR RUNNING HOT.—Causes (a) excessive oil—drain case and put in correct quantity, (b) slipping clutch—due to an obstruction on the propeller or a bent blade (ac) heat generated at the rear bush
(par 56).

56. BUSH AT REAR OF REVERSE GEAR RUNS HOT. —Causes (a) lack of oil due in turn to oil leakage—renew oil according to instruction plate, (b) shafts out of line— remove shaft coupling and check alignment of shafts with steel rule or with the blade of a carpenter's square (par. 59).

57. TO DISMANTLE REVERSING GEAR.—Remove cover, find spring link in chain, remove chain, detach case from engine. If it is necessary to remove the upper wheel draw out spindle with stud and cupped washer, in tool box. Do not remove upper wheel unnecessarily.

58. TO REPLACE REVERSING GEAR.—Attach a length of string to each end of the chain, pass the chain below lower wheel, lay surplus on top of wheel so that gear case will pass over it, or by using a wire hook to fish up end of chain it may be shipped after gear case has been attached to engine. Permit nothing to fall into gear case—keep it covered. A small part dropped in accidentally may be recovered through bottom flange. Mesh control chain so that shaft is at mid travel (neutral) with knob of wheel down.

59. SHAFT COUPLINGS must be very tight. If once they slip both coupling and shaft become torn and ruined. All parts of the shaft coupling should be painted before being assembled. If shaft runs out of truth it is probably due to unequal tightening of shaft coupling bolts. Hold a pencil to the running shaft and tighten the bolts at the side marked by the pencil.

60. THE SILENCER contains nothing but an internal pipe which leads the exhaust to the top. If the bottom of the silencer is below sea level water will get into the engine and ruin it at once. In very deep boats it is necessary to raise the silencer on a standpipe to bring it above sea level. It is common practice to bend exhaust pipes up to the deck and down again. This may be effective in preventing water passing from the sea into the silencer, but it also prevents water passing from the silencer to the sea when the engine is being turned by hand. Under such conditions the silencer fills with water which then overflows by the internal pipe into the engine. The following must be observed—(a) Point of discharge through hull slightly above sea level. (b) Silencer above point of discharge, (c) No part of exhaust pipe higher than silencer.

61. SILENCER MORE CONVENIENT AT FRONT END. —In certain boats the silencer and exhaust pipe are less of an obstruction at the front end. To make the change the manifolds are simply assembled end for end and the vaporizer and other parts will be found to suit. The only part required new is the control rod connecting governor lever with throttle. The level of the float chamber may require adjustment (par. 30).

62. THE EXHAUST MANIFOLD must be jointed to the cylinder with care. The cylinder holding down bolts should be slackened while the manifold is being tightened to the cylinder. Do not neglect to tighten the cylinder holding down bolts. The joint is asbestos covered with copper and requires to make it water-tight an oiled paper joint each side. The copper asbestos joint withstands repeated use, but the paper joints perish each time the manifold is removed, and replacements should be carried in reserve. Drain the cylinders of water before removing the manifold.

63. FLYWHEEL —To remove flywheel take off nut. strike end of shaft with a hammer weighing at least 3 Ibs. while applying a piece of wood behind wheel as a lever. Protect end of shaft with a piece of copper or brass while striking it.

64. THE STERNTUBE must have the stuffing box OUTSIDE in order to keep out sand. It is not desirable to fit two stuffing boxes because (a) that permits the neglect of the outer or more important one and (b) causes quite a considerable and unnecessary friction. Outside stuffing boxes should be tightened each time the vessel is ashore for cleaning—neglect to do so may involve the cost of having the vessel laid ashore. If you have no proper-packing use rope yarn and tallow—mineral grease is not so good. Avoid packing which contains india rubber or anything sticky. Secure the packing screws with Monel wire. Copper wire does not last.

65. PROPELLERS should be removed with a heavy hammer—a light one harms the propeller without removing it. Secure the nuts with a turn of Monel wire through the end of the shaft. If you consider the propeller unsuitable for your boat report to us the length, beam and draught of the boat, the speed of the engine with the throttle held fully open, and the markings on your propeller.

66. TANKS must be fixed sufficiently high to feed the float chamber. (For Dimensions see Engine Catalogue). If the
tank is aft of the engine a margin in height is necessary to allow for the sinking of the stern when the boat is under way, Petrol tanks are undesirable below deck and positively dangerous where lamps are ever present. They should be installed where exposed to the open air. Tanks although galvanized, soon rust unless protected by paint.

67. JOINTS.—Each boat should carry a stock of all joints. We can supply them. In cases of urgency joints can be cut from certain materials ordinarily obtainable from mill furnishers and plumbers. For exhaust use "asbestos millboard" coated with black lead to prevent adhesion ; for water connections use " rubber insertion." Red fibre withstands oil and water, but not heat. Anything containing india rubber does not withstand Petrol, Paraffin or Oil, for which use cloth or paper saturated in syrup or treacle-

68. BALL BEARINGS.—The failure of ball bearings is seldom due to fair wear and tear or to original defect, but almost always to lack of protection from damp or to defective mounting. As soon as the burnished surface of the balls shows rust the failure of the bearing is imminent. A "Thrust" Bearing consists of two loose washers with a ring of balls between. When the two washers are quite alike the reassembling of them presents no difficulty, but when the one washer is larger in the bore than the other the two must not be interchanged. "Journal" Bearings consist of two rings with balls between. The inner ring must be a press fit on the shaft and the outer ring must be a sliding fit in the housing. Ball bearings having a broken ball cannot be repaired, but if all trace of the broken ball is removed the bearing may run for a considerable time.

69. IN FROSTY WEATHER all water must be drained from the cylinders, from the pumps, and from any pipe bend where water could lie. The cylinder drain is on the starboard side.

70. WINTERING.—Before laying up an engine for the winter it is very important to remove any salt dried on to it as this draws the damp and causes an excessive rusting action. To do so wash down the engine with hot water applied while the engine is still warm enough to dry itself. Drain all water from the cylinders, from the pumps, and from any pipe bend where water can lie. Pour some lubricating oil into each cylinder and turn the engine by hand. Coat everything not protected by paint with vaseline.