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Factory Parts/Service/Sales Bulletins

Although not a true Factory Bulletin, the following article that first appeared in the July/August, 1999 issue of the Maple Leaf Chapter's PROP WASH newsletter is a well written and easily understood treatise on probably the most commonly asked and misunderstood questions concerning old iron.  Reprinted by permission of the Maple Leaf Chapter, Antique Outboard Motor Club, Inc.

by Ivan Renton

Let's get right to the main point.  What type and how much lubricating oil does your motor require?  The motor designers deliberately selected the type and quantity of oil.

Tests were conducted, the type of oil selected and the quantity, expressed in ounces per gallon, was determined.   The tests considered the effects on compression, operating temperature, lubrication, deposits, wear, starting characteristics, smoke, thermal efficiency, corrosion and cost.  They were cognizant of other motor manufacturers' practices and dealer reports influenced the decision taken.

Once settled, the type and quantity of oil was displayed on the engine and in the operating manual.  The specification remains valid today despite improved oils and sparking plugs.  Let's see why.

It was soon discovered two-stroke motors like the higher viscosity oils.  SAE 30 or 40 performed well.   Even 60 in racing engines.  The higher viscosity improves compression and lubrication.  Today's two-stroke oils are formulated to SAE 40.  So, no change here.

So the decal shows one-half pint of Gargoyle Mobil Oil "B" or extra heavy oil to one gallon of gasoline.   How much do we add using today's oil?  The same.  Remember the tests?   Oil volume per gallon affects compression, lubrication and operating temperature.   The first two are easily understood, the third requires some explanation.  A fair proportion of the lubrication oil passes through the combustion chamber unburned.   This finely disbursed mist has mass and weight, absorbing combustion heat and reducing the operating temperature of the motor, so no changes here.

Older outboards have gear cases without oil seals, consequently, when the decal shows to use grease, it means grease and not oil.  What type of grease do we use today?  One approach is to mix a little 90 E.P. gear oil with General Motor's Lubriplate #105.  Another similar solution is a little 90 E.P. gear oil mixed with CTC's multipurpose E.P. grease.  The 90 E.P. gear oil reduces the tendency for grease to channel.  Draw a screwdriver blade through a grease sample and observe the channel.

During the 40's, the outboard motor industry realized the advantage of hypoid gear oils.  The gear case was redesigned to include seals necessary to keep water out and the 90 E.P. oil within.   If your motor has seals, use the oil, if not, use grease.

Now let's dig a little farther into our bag of lore and see what we find.

Early motor oils were known to be unpredictable, their characteristics varied.  Engine designers commonly specified major oil company products for their motors.  This was the only way they had, the reliable standard test methods and knowledge common today was absent.  Still, the oil was a problem.  Viscosities, ash content, impurities, difficult mixing, clogging and deposits, to name a few.  Many communities were forced to rely on automotive products, few choices were available.  This made the oil dilemma worse, and considering the 60 octane gasoline, feeble spark plugs, and stiff cranking engines, think of the despair suffered by motor operators.

During the 50's, two-stroke outboard motor oil was developed.  Improvements continued.  Today's oils are cleaner, ashless, with safe detergents, stable viscosity, consistent quality and easy mixing.  At least some are.  Some are not.  Motor manufacturers continue recommending oils suitable to their motor's requirements.  Some even have their own oils produced to their particular specifications.

Motor performance is enhanced when the same oil is used, mixed the same accurate way with fresh gasoline.  Carb adjustment is minimized, starting made easier.

Bearings, plain, ball or roller, will not perform properly unless clearances are correct, adequate oil is present, surfaces are clean, water and dirt is excluded.  Old motors, long out of service, should be dismantled, bearings inspected, and corrections made.   As a minimum, fog oil into the crankcase and cylinder, prior to hand turning the crankshaft.  The practice of breaking-in uses moderate engine RPM and double the usual oil content to remove minor bearing high points.  Useful for new bearing components or adjustments and for long-stored motors.

Outboards using plain bearings experience almost all bearing wear on start-up and until operating temperatures occur.   During this phase, the bearings require excess lubricating oil.  This requirement is an important consideration when deciding on the oil/gasoline mixture.

The Johnson Service Manual suggests oil type and quantity be checked where poor compression exists.  Also, they suggest for working engines, the oil quantity be doubled.  Working engines, in this case, means engines subjected to extended usage.  Purists wanting to replicate the original operating conditions could search out a supply of 100% pure mineral oil or SAE 40 non-detergent motor oil.  Take care to carefully mix these products with gasoline before adding to motor fuel tank.  Also, note these oils tend to separate after storage.

Gear cases have an interesting history.  The early bevel gears commonly failed in service.  Scoring, galling, corrosion and abrasion, were not controlled.  The lubricant, grease, was the cause.   Lack of attention, difficult to replace, no protection against metal to metal contact and abrasive impurities were known problems.  As engine horse power and RPM's increased, new solutions were found.  Gear systems were redesigned and extreme pressure hypoid gear oil developed.  Seals were used to keep water out and oil within.  Proper replacement of this oil is still a necessity and lack of attention is common.

Where does the new synthetic oil fit in the lubrication scheme of things?  This writer is not sure.  Much controversy surrounds these products.  There seems to be no compelling reason to use synthetic oil in the old outboards.

For further reading, try Marks Mechanical Engineering Handbook.  Commonly available in public libraries.   Gears, bearings, lubricants, metals, clearances are some of the topics of interest.

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