1940 Kiekhaefer Mercury Outboard Service & Repair Manual

-l SERVICE MANUAL MERCURY Outboards 1965 and Prior c-90-25500 www.repairmanuals4u.com

TABLE of CONTENTS Mercury Models l94O thru 1965 SECTIONI - GENERAL INFORMATION . TUNEUP and SERVICE HINTS Page General lnstructions . , . . .1 Fueland Fuel Mixing Procedure . . . . . 3 Cluicksilver2-CycleEngineOil ..... 5 QuicksilverEngineCleaner .. .... 6A Anti{orrosionlubricants ..,...68 LubricantGuns ...68 OtherMarineLubricants ...68 Principleof Operation-2-CycleEngines ..... 7 Boat Performance and Propeller Selection . . . . 8 We?ther Affects Engine Performan@ . . . . 9 TheoryofPropellerPropulsion ......... 9 High-PerformancePropellerselection ... . . 10 CuppingPropellers . .... 10 PreventiveMaintenance .. .. 11 SpecialCareRequired .,..13 MotorTroublesCauseandEffect . ....... 14 TroubleChart. ,,., .... 15 OutboardTuneup . .. .. .. n SECTION II - POWERHEAD SixMainTypes ......... 1 Part'sInspection - How to Check . , . .2 MarkTTypePowerhead .... 5 lVhrk6TypePowerhead ....... 11 Mark25TypePoraerhead ....... 17 4€ylinderModelsPowerhead .. ....... 24 6€ylinderModelsPovrcrhead .. ...... 36A 2€ylinder Splint Crankcaee Powerhead . . . 47 2€ylinderFull GearShiftPowerhead . .. ... . ,..57 SECTION III - LOWER UNIT GMainTypes ......... 1 Part'slnspection - How to Check . . . . 2 Mark6TypelowerUnit ........ 3 Gear Shift Type Lower Unit - All 44y1. Models (Without Jet Prop Exhaust, exceptMark rrc & KFg-KGg)& 2€yl. Mark2$2o-1 5&KH7 . ...... 10 Non-ShiftTypeLowerunit .. ........ 21 "K" ModelTVpe Lower Unit . . . . n Dyna-FloatSuspension .. .. :B 6{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{{yl. DirectReversingLeftHandRotation . . . . . .37 TransmissionRepair-2-Cyl.Models ...... 43 OuicksilverGearHousings ..... 47 2€yl.TransmissionType ..... 51 Direct Reversing Right HandRotation . . . . 57 Merc800-7fl) Dir. Rev. LH Rotation . . . . 66 Merc800-70O Dir. Rw. RH Rotation . . . . . 73 Merc 1 1 fi)-l 1 fl)Ss-l fl)O€sO€ 5059900-850-&)0-700-650 Full GearShift ..... 79 Merc2(X)-l 10-d)-SlFull Gearshift ...... 87 Merc5fi)-450-350 (2{yl.l Full Gear Shift Jet Prop ExhaustType . . . . . 95 HeavyDutyWaterPumpKit ... ...... 103 TrimTablnstallation ..103 SECTION IV. IGNITION General lnformation . . . . . 1 MagnetoServicelnstructions .-...4 SparkPlugs ..... 5 SparkPtugElectrodeBurning ..... 8 OuicksilverEngineCleaner ..... 9 PhelonMagneto-2{ylinderEngines .... 11 Synchronizing Breaker Points - 2-Cyl. Engines with EarlyorlatePhelonMagneto ....... 13 TestingwithMagnetoAnalyzer .... 16 ScintillaMagnetoParts .. ..... 17 BreakerPointsettings ...17 ScintithM4neto-2-CylinderEngines .... 19 Page Magnetosfor4-CylinderEngines .., ..... 23 lgnitionDistributorRepair-&Cyl.Engines . . . . . . . 3 SuppressionofRadiolnterferen@ ...... 364 Timing-Adjusting-Testing-Mark78-78A-75-75A . . . . 37 GCylinderDistributorBreakerPoint . ..... 41 Timing-Adjusting-Testing ...€ Merc5004504OO-35O-ilD& Mark58-58A-55A-35A . . . . /K' iilark10"10A-15A .... 4.5 lVferclfi)-150-200-250andMark28-28A . . . . . . 47 LeadWireShield-Merc20o-llO€0 . . . . . . . . . . 48A Magneto MountingModification - 2Cyl. Models . ' . 488 Timing-Adjusting-Testing .'...49 Mark5SSSE . . . . . .. 4(, Mark25 . ..53 fvlarkS)-30E . .. .. .. 55 1ilark55H-30H . .. .. 59 Merc70O€OODirectReversinS . .. . , ..., ..61 MercS(X)DirectReversirg .... 66 Merc85006Cu. ln.)-80O-7O0 Full Gearshift . . . . . . . . 71 lvlerc100O€50 (9O Cu. ln.) . . . Tl Merc6SO ........ 81 Merc350(2-Cvl.) ..... 85 lVlerc 2fi) Full GearShift . . . . &, Merc110-75-6rG4O-3P . ...... 91 SECTION V. CARBURETION General lnformation . . . . . . 1 Carburetion-PreliminaryOheck ...,2 General ServiceHints .... 3 TypesofCarburetors-Adjustment .., ..... 4 PressureFeedCarburetor(TillotsonTypel . . . . . . . . 6 GravityFeed ..... 9 CarburetorDrillChart-Mark&"K"Models . . . . . 10 CarburetorDrill Chart-MercModels ..... 11 CarterCarburetor-Mark20Hand55H .. ... 14 CarburetorConversion-Mark55H-20H . . . . . . . . 16 CarburetorAssemblies-24+Cyl.Engines . . . . . . . 18 ModelKACarburetor ..... 19 SECTION VI - FUEL SYSTEM PressurizedFuelTank .. ...... . 1 VacuumFuelTank ...... 5 OtherFuelTanks .... 6 FuelPumps ........ 8 SECTION VII . STARTERS Description . ' . .. .. .. . 1 Magna-Pultstarters .... . 1 AutomaticRewindStarters .. .. .. . 3 MercElectricstarting-Positi\reGroundType . . . ' .. .5 Electricstarting ... '. '6 BatteryandElectricAccessories . '.. '7 Winterstorageof Batteries ...... '8 Disassembly of Starter Motor ' . . .9 Disassembly of MercElectric Components . . . 10 Reassembly of Staner Motor . . . 12 Reassembly of MercElectric Components . . . 13 f nstallation of Starter and Components . ' . 14 MercElectriclgnition&StarterSwitches .... 16 RectifierCheck. '...-17 Alternator ...18A lgnitionReplacementKey&Coit ..'..'18A BatteryMeterlnstallation .'...18A StarterArmRepair ..... -.18A StarterSolenoid .... ' ..... 188 MercElectricTesting&Troublechart ' ' ..19 MercEfectricstarterSystem-Components . . - -' .21 Harnesses - 4-Cyl.2-Lever Electric Control ' . . . ' . .22A - www.repairmanuals4u.com

- Page ExternalHarnessA-3gl2s ..,..22A Wiring Diagram - zl-Cyl. Single Lever Remote Control . . , . . 22[3 American.Bosch Starter lvlechanism and Starter ll/lotor . . , . . .23 Delco-Remy Starter Mechanism and Starter Motor . . . n Nanr6€yl.Delco-RenryStarterMotor ..,..O Delco-RemylnertiaTypeDrive ...... ,31 StarterMotorTestingandTroubleChart . . . . . . . . . 32 Mark25EStarter-NegstiwGround ...... 3!l WiringDiagram-Mark25E .,...34A WiringDiagram-Mark78-75 . ,. ..36 Harnesses-Mark78-75 .,..36 ReversingType4 &8 Brush MercElectricStartorMotor ., . . . Sl CheckingAmperageOutput-MercElectrics . . . . ,, . tlO WiringDiagram-lvlarkTSA-75A . .. .. .. 41 f nternal Harness - Merc 8d)-700€OO Dir. Rev. , . . . . 42 fnternalHarness-Mark78A-75A ... ..... 42 WirirB Diagram-MercS0O-7d)€OODirectReversing . . . . . . € Wiring Diagram-Merc85D80O-70OFull GearShift . . . . . . . 4 InternalHarness-Merc850€fi)-7(D Full Gearshift . . . . . . . 45 InternalHarnes-Merc350(2-Cyl.) ...... 45 WiringDiagram-lVlerc35o(2-Cyl.) ....... 46 Wiring Diagram - Merc 1000€O0€50-700 Full Gear Shift . . . . 47 WirirBDiagram-MercllOOSS-9SOSS ..... t|8 hfirirqDiagram-Mercllfl)€5O ...49 KiekhaeferstarterMotor-GCyl.Starting t966 . ., . . 50 American-Bosc*rStarterMotor-4€yl.Startiqg 1965 .. . . . . 51 SECTION VIII . MISCELLANEOUS OutboardEngineSpecifications ., ..,.,.,1A TorqueSpocifications. ,...5A GearRstios ..... 6A Pago Capacityof LubricantinGear HousinS . . . . . . . , . .64 Transom MountingSpecifications . . .74 Lubricant and Sealer ApplicationChart . . . . 8A Outboard LubricantandMaintenanceChart . .. .. .. 9A TopandSideCowls ..... ,18 Decals-Application .- .... 28 BottomCowl .. .. 48 ThrottleandshiftMechanismandSteeringHandle, . . . . . . . lC Throttle and Shift Control and Steering Handle for ll/brk g)-1-2-3 . . llc Throttle and Shift Control and SteeringHandlefor tt/lark 3) . 1S Throttle€teering lhndle Ass'y & CoPilot - 4{yl. Engines , . 15C Throttle€teering Handle Ass'y - 30 Cu. ln. 2€yl. Engines . . , 16C SteeringHandleAsserblyforMerc3sO . . . . . . . . 18C Steering HandleAssemblyforMerc5OOM ., . . . . . 21C RideGuidelnst€llationDimensions ....... lD Ride€uideCableMecurements ...lD RideGuidesteeringWheel Dimensions . . . . . . . , . .2D RideGuideSteeringwheel lnstallation ... . .. ,. ..3D Standard RideGuide Engino Attachment . . .6D RemoteThrottle-ShiftControls .. . . lE Two-Lewr RemoteControls-lnstallation . . . . , . . . 3E Steering Bar Installation . . .48 Two-LeverRemoteControls-Repair . ..... 5E Controls for 6€yl. ElectricStaningDirect Rorersing Modefs . ..... 7E Controf for2-$6Cvl.FullGearShiftModels . . . . . lOE @ntrol for 2-C!1. Manual StartingEngines - Automatic TransmissionType. ..13E www.repairmanuals4u.com

- IITITTII e .... -atio ati o tl p ilTlllll l|iltl llllllll general inf orrrr lilillll ililil11 r tuneu ill|lll llllllll hints &se o roe Y iililll llllll www.repairmanuals4u.com

INDEXISECTIONI'GENERALINFORMATION Page General Instructions ........ 1 ServiceRecommendations ....... 1 Directional References ..... 2 Ratingof Outboards-MercuryHorsepower . . . . . . . . 2 Ouicksilver2-CycleEngineOil ... ..... 3 OuicksilverEngineCleaner ..... 5 HowtoUse ..... . 5 OtherSuggestedUses ...... 5 Anti€orrosionLubricants ..... 6 LubricantGuns ..... . 6 OtherMarinelubricants ...... 6 StorageSeal .. .... 6 MarineCleaner . .. . 6 CorrosionandRustPreventive ..... 6 PreventiveMaintenance ....... 7 LowerDriveUnitLubrication. . .... 7 LubricationChart . . ... ,..7 25-HourCheckup .. ... ... 7 SpecialCareRequired ... .... 9 RustPrevention .. ....... 9 Preparation for Storage or Shipment . . . . . . . 9 Attention RequiredFollowing Operationin Salt WaterorSilt .. ...... 9 PaSe Attention RequiredFollowing Complete Submersion ..... 10 MotorTroublesCauseandEffect ..... 10 TroubleChart . ..... 11 OutboardTuneup .... 16 Description ..... 16 TuneupSequence .. ... .. 16 TuneupSequenceServicing ...16 "l"Compression.. ..... 16 "2"SparkPlugs. ....... 16 "3"Carburetors . . . . . . ,17 "4"FuelSystem ....... 18 "5"lgnitionSystem ..... 19 "6"StarterMotor&Solenoid ..... 20 "T"Alternator&Rectifier ...n "S"fnternal WiringHarness ...... 2O "9"LowerUnit&WaterPump .... 21 "l0"AdjustmentsPriortoTesting . . . . . . . 21 "1 1" Test Tank Procedure . . . . 21 "l2"BoatTest ...21 "13" Additional Checks and Adjustments . . . . . . . 22 WaterPressureTest -..22 FuelPresureCheck ...n - REVISED JUNE 1971 KIEKHAEFER MERCURY, FOND DU LAC, WIS.#935 PRINTED IN U.SA, www.repairmanuals4u.com

I TIASTER SERVICE TIANUAT G eneral I n structlons SERVICE RECOMMENDATIONS Your new Master Service Manual includes all of the important general and detail informationon all Kiekhaefer MercuryOutboard Motor models. All material is compiled from former aervice manuals, owners'guides, service bulletins and other sourcoe, relative to indir.'idualMercury engines, and brought up-to-date. New and revieed pages are added periodically to Franchised Kiekhaefer Mercury Dealere only -- to keep the book cunent. (observe dateline at bottom of each page.) In preparation of this book, careful consideration was given to all adjuet- ment and service operations, maintenance and repairs which are encountered in the operation of internal combustionengines, specifically the Mercury Outboard Motor. In the text, "suffix models" (e.g. Merc l250Bp, Merc 650-5, Mark 20H) are included in the instructions for the basic model (e.g. Merc 1250, Merc 650, Mark 20), unless listed separately. The procedures followed are based on a general overhaul. Refer to the dealer's Mercury Parts Manual for all correct partst numbers. For tools, which are referred to in this manual, see Tool Section IX, if the correct use of the tool is in doubt- Specifications for all models are listed under "Master Speci- fications Chart", Section VIII. IMPORTANT: Major repairs, particularly those which require ertensive disassembly or replacement of internal parts, should be done only where the necessary factory-designed toois ond equipment are at hand.. Section | - General Information \laster Servi ce \lanual Revised Aug. 1969 Page I www.repairmanuals4u.com

I DIRECTIONAL REFERENCES In this book, all directions are given as "righttt or "lefttt as they appearwhen viewing the boat from the stern (rear) AFI or SIERN PORT ( tEFT ) STARBOARD (RIGHII Figure l. Directional References looking toward bow (front). In marine publications, "righttt is known as "starboard" and "lefttt as "port". (Figure l) RATING OF OUTBOARDS .MERCURY HORSEPOWBR Horsepower ratings for Mercury Outboard Motors are in terms of standard horsepower, as recognized and used internationally by the Society of Automotive Engineers, the American Institute of Electrical Engineers, the American Society of Mechanical Engineers and the American Society of Civil Engineers for rating electric motors, diesel engines, steam engines, marine engines or any other prime movera. A standard horsepower is defined as the amount of energy reguired to raise 331000pounds one foot in one minute. Not only are Mercury Motors rated according to this world standard of horsepower, they are also rated at safe, continuous duty ratings rather than flash peak ratings. This means that instead of being given a horsepower designation based on the peak Performance of a new motor (a rating which that motor may not attain again in normal operating conditione), Mercurys -are rated at the horsepower they'll deliver month after month, year after year. Just as the definition of horsepower is unusual, so too is the method of computation. The Engine Test Code of the Society of Automotive Engineers standardizes the computation of horeepower from the data obtained on the dynamometer, or power.measuring device, correcting all values to the power which the engine would produce at sea level altitude and the 60oF (I5.5'C) temPerature. It is in ttre choice of conditions at which the rated or advertised horsepower shall be taken that various manufacturers differ, some taking flash or peak readings obtained during ehort bursts of full Power oPeration' while others are more conservative in using conditions of steady operations at safe working revolutions per minute. Kiekhaefer Mercury rates its Mercury Outboards at the horsepower which they will develop when run under continuous duty at nomal operatingspeed, holding a little extra power in reserve for higher speed operation. Then too, it takes more than rated horsepower alone to provide top performance for the outboard user. Outboard horsepower is measured at the engine crankshaft and does not account for losses encounteredin the exhaust system or in the gears and bearings joining the crankshaft to the propeller. Here Mercuryts vacuum exhaust and full-jeweled design insure that the largest possible percentage of that rated horsepower reaches the propeller without being lost in friction or in the exhaust system. Then Mercury's modern propeller design takes over to convert that horsepowerto the thrust or push needed to propel a boat at maximum speed, the correct design of the underwater structure minimizing hydrodynamic losses. Page 2 Master Serviee Manual Revised Aug. 1969 Seetion I - GeneralInformation www.repairmanuals4u.com

FUEI qnd FUEIttlXlNG PROCEDURE It is recommended that regular leaded automotive gasolines !g uled- in Mercury Outboards which are equip"ped wi th Thunderbolt Ignition Systemsand Polar G"p Spu.k plugs. (Figure l) Some marine white gasolines have been known to give trouble because of their very low octane number. theLbv causing detonation, or to their "dirtytt components whicir cause ring sticking and port plugging. Regular gasolines are of a more closely-controlled, uni- form quality and are readily available at any service station or marina. Figure l. Polar Gap SparkPlug Figure 2 Conventional foark Plug Merc-ury- Outboards with conventional ignition systems and spark plugs (Figq: 2) operate with higher plug temperatures than those with Thunderbolt Ignition. Thi"-r"quires that they be operated, preferably, on non-leaded, white fuels such as marine or light aircraft or low-lead content gasolines. Any Mercury Outboard !n-gin-e maybe operated satisfactorily on white gasolines of high quality -known to have been satisfactory in the past. RECOMMENDED FUELMIXTURE Use only AUTOMOTM REGULAR or Amoco lead- free premium gasoline in all engines which have Polar Gep spark plugs. (Figure l) Marine white, automotive white, light aircraft or Amoco lead-free premium gasolines are preferred for oider Mercury Outboards with conventional spark plugs. (Figure 2) If not available, use good grade automotive gasoline. AUTOMOTM PREMIUM gasolines should not be used, since they eontain harmful additives. I. When using new FORMULA 50 Quicksilver 2-Cycle Super OutboardMotor Oil, thoroughly mix one l2-ounce can with each 5 gallons of gasoline (8 ounces with each 3 gallons) in your remote fuel tank. (Figure 3) Section l- General Information I 2. D. If using Formula 2 Quicksilver 2-Cycle OutboardMotor Oil, thoroughly mix one 30-ounce can rvith each 6 gallons of gasolineor 15 ounceswith 3 gallons in your remote fuel tank. In emergenc)', when new FORMUL-{ 50 and Formula 2 Quicksilver Oil are not available, substitute a high quality Z-cycle oil that is intended for outboard use. Use manufacturer's recommended gasoline-oil mixture. CAUTION: The use of other than FORMUAL 50 Oil in the 50:l ratio may cause piston seoring, bearing failure or both. Do not, under any circumstances, use multigrade or other highly detergent automobile oils or oils which contain metallic additives. This type of oil may result in piston burning, scoring or both. OPERATION IN CANADA: Use 15 ounces of FORMULA 50 Quicksilver 2-Cycle Super Outboard Motor Oil to each 5 Imperial gallons of gasoline or 35 ounces of Formula 2 Quicksilver 2-Cycle Outboard Motor Oil to 5 Imperial gallons of gasoline in the remote fuel tank. See your Mer- cury dealer for approved oils in your area. Figure 3. New FORMULA 50 Motor Oil CORRECT FUEL MIXING PROCEDURE Observe fire prevention rules, particularly in the matter of smoking. Mix fuel outdoors or at least in a well-vent- ilated location. Mix fuel directly in the remote tank. Measure accurately the required amounts of oil and gasoline. Pour a small amount of gasoline into remote tank and add a small amount of oil (about the same amount as gas). Mix thoroughly by shaking or stirring vigorously; then addbalance of oiland gasolineand mix again. Clean- liness is of prime importaice in mixing fuell as even a verv small oarticle of dirt can cause carburetion trouble. Revised Aug. 1969 Page 3 www.repairmanuals4u.com

I Always use fresh gasoLine. Casoline contains certain gum and uamish deposits and., when kept in a tank for a length of time, rnay giue carburetortrouble and cause sparh plug fouling. BREAK-IN PROCEDURE FOR FUEL-OIL MIXTURE CAUTION I. New FORMULA 50 Quicksilver ?Cycle Super Outboard Motor Oil For the first two tank-fulls, thoroughly mix two llounce cans to each Ggallon tank of fuel (or one l2-ounce can to each Lgallon tank of fuel). After break-in, refer to "Recommended Fuel Mix- ture", preceding. 2. Formula 2 Quicksilver ?Cycle Outboard Motor Oil For the first two tank-fulls, thoroughly mix one 30-ounce can to each Ggallon tank of fuel (or 15 ounces to each 3-gallon tank of fuel). Nter break-in. refer to "Recommended Fuel Mixture", preceding. 3. Operate a new moror at %-throttle (2500-3500 RPM) for 2 hours. After 2 hours, the motor may run at any speed, although sustained operation at full throttle should be avoided for an additional 8 hours. NOTE: If using metric or Imperial tneasLLre, one U.S. ounce is .03 liter; one U.S, gallon is .83 Imperial gallon or 3.8 liters. IMPORTANCE OF CONSISTENTFUEL MIXTURES Carburetor idle adjustment is sensitive to fuel mixture variations which result from use of different gasolines and oils or due to inaccurate measurinsor mixing. This may necessitate frequent readjustment of the carburetor idle needle. Be consistent. Prepare each batch of fuel exactly the sameas previousones. (l sing less than the recom'mend.ed proportion -of .oil- maylesult in uery serious motor damage due to lack of "riliri"ot lubrication. (l sing rnore than the rec ommended proportion of oil uitl cause spark plug t'ouling, erratic c arburetion, exces siu e srnoking and faster-than'normal carbon accumulation. CRUISINGFUEL ECONOMY A special feature of 4 and 6-cylinderand Merc 350 models p.ouid"d far greater fuel economythan ever before provid- "d on uny ouiboutd motor. This is obtained by a specially designedlinkage between the carburetor and ignition -system. It is automatically broughtinto operationby pulling control Iever back to give cruising speed 70 to 90 percent of maximum speed.The special featureincreasescruising range (or miles per gallon) and reduces fuel consumption (gallons per hour). WARNING TO MERCURY OUTBOARD DBALERS AND OWNERS WnnntNC, The use of any other oil than Kiekhaefer Quicksilver FORMULA 50 Oil in the 50:I ratio may cause piston scoring, bearing failure or both' The motor warranty may be void if failure should occur with the use of other oils in the 50:I fuel-oil mixture' Examination of outboard motors with scored pistons, which have been returned to our Service Department, show that the use of certain types of so-called "outboard motor oilst'have caused piston scoring. Do not -- under any circumstances - use multi-grade or highly detergent automobile oils or oils which contain metallic additives in any fuel mixture. This type of oil may result in piston burning, scoring or both. Page 4 Revised Aug. 1969 Section I - General Information www.repairmanuals4u.com

- QUICKSILVER 2.CYCLE ENGINE OIL Good Ingredients And ProperChemicol Composition Are Bosic Requirements ForOutboord Engine Oil. ltosr Top QuolityAutomobile 0ils Are l'lotAcceptoble For 0utboord MoiorService A universal, all-purpose lubricant to accommodate every conceivable application requirement would certainly have tremendous military and industrial advantages. Yet lubrication engineers continueto develop ever-wider varieties of special lubricants for special appli- cationslike jet engines, Diesel engines, firearms, speedometers, gyroscopes, refrigerators, water pumps, air com- pressors, vacuum pumps, electric motors, electric generators, hydraulic controls, hydraulic power systems, dif- ferentials, torque converters, transmis- sions, power steering mechanisms, chain saws, tank tracks, chain-and- sprocket drives, power tools, calcula- ting machines, typewriters, printing preases, steam turbines, textile machinery, steel mill machinery, fishing reels, clocks and wat- ches. The familiar words, "good and propertt, are particularly ap- propriate when applied to lubricants, because GOOD ingredients of PROPER chemical composition are necessary to achieve satisfactory performance, reliability and service life of the equipment in which a lubricant is used. For example, in an automobile such as you drive, the engine alone requires three different kinds of oil, depending upon sub-zero, cold or hot- weatherdriving conditions.In the transmission, at least two different kinds of oil are used, depending upon whether it is a conventional shift or an automatic transmission. In the rear axle, at least two different types of lubricant are used, depending upon whether it is a conventional or a "limited slip" differential. Isn't it reasonable that the high- precision outboard engine, yielding rnore horsepower per pound than anystandard- production internal eombustion engine and admired by the rest of the engine Section I - General Information industry aa a marvel of compactness and durability, should require a special lubricant? Base oil quality is only one factor determining the suitability of a lubri- cating oil for any particular engine. An oil rated as "excellent" for automobile engines would most likely be rated as "unacceptablet' for outboaril motor use. One reason is that automobile engine oil contains a special additive which is essential to protect the very highly-loaded cam and lifter surfaces in the valve gear of modern engines from scuff and wear. Oil is exposed to high temperatures in 2-cycle engines, and automobile oil would break down to form harmful deposits which may promote pre-ignition. Some automobile engine oils are made so that they do not readily mix with gasoline. This is desirable to prevent dilution of sump oil but may promoteseparation in a 2-cycle engine fuel mix. Gasoline-oil separationputs a layer of oil at the bottom of the tank, with gasoline at the top and various propor- tions ofgasoline and oil between. Since the fuelpick-up is locatedat the bottom of the tank, the engine may get a high proportion of oil when the tank is full and almost straight gasoline when the tank is nearly empty. Therefore the engine may smoke excessively and foul plugs at first, then overheatand possi- Master Serviee lllanual bly score the pistons becausethe remai- ning fuel contains insufficient oil. There's another reason why high- quality automobile engine oils are un- acceptable for outboard engine use: The advent of high-compression, high-output automotive engines presented new lubrication problems which necessitated the addition of detergents to the oil for the purpose of inhibiting varnish for- mation and piston ring sticking. Most of the detergents used are metal com- pounds. In four-cycle automotive engines, the oil is effectively confined to the crankcase and very little leaks past the piston rings into the combustion cham- ber. In a two-cycle engine, the oil must be mixed with the gasoline and so practically all of these metallic deten- gents enter the cylinders (above the pistons) and form ash deposits when they come in contact with the hot surfaces of spark plugs, piston crowns and combustion chambers. These deposits may become incandes- cent on exposure to the combustion flame, causing preignition and detonation which result in piston crown burning, piston scuffing and cylinder wall scoring. Frequently metallic deposits bridge a spark plug gap so it cannot fire. Oil testing is a ceaseless operatiorr at Kiekhaefer Mercury, primarily to keep in touch with developments in oil refining and additives made by others and to test our own modifications made for the improvement of our oils. To properly evaluate the suitability of oils for various applications, it is necessary to understand something about the nature of oils. For example, no two Revised Nov. 1969 Page 5 www.repairmanuals4u.com

1940 Kiekhaefer Mercury Outboard Service & Repair Manual

You're Reading a Preview

Recently Viewed