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Frequently Asked Technical Questions
Can I use regular gear lube in my "Old Merc"?
  Mercury originally recommended a light grease in all 1961 and older 1, 2, and 4 cylinder models except the 1961 Merc 500. Grease was also recommended in the 1962 Merc 250. We still feel this is the best choice for these older motors. We carry 105 Lubriplate, which is the equivalent, in a 10 oz. tube.  
      For Mercs newer than this, we carry and recommend Mercury's Premium Gear Lube.
How much is my old outboard worth?
  This is not an easy question to answer, as it is dependent on many factors such as cosmetic condition, mechanical condition, region, rarity, etc. We are not able to offer appraisals.  The best place to find information on the value of old outboards is in Peter Hunn's The Old Outboard Book Volume III.
I have the service manual and I've tried everything and can't get my engine to run properly. What can I do??
Most people can't find competent professionals to work on old outboards. Shipping a motor far away for service is a poor solution. The best solution is to be able to work with someone else "hands-on." Friends who tinker with engines are the first choice. Two heads are always better than one, even if your friend doesn't know outboards. Joining the Antique Outboard Motor Club and getting to know the fine hobbyists in your area can be very helpful.
They are often willing to share their knowledge and try to help someone who has tried to help himself. Internet chat groups may also be a source of suggestions. Ask a member on the Antique Outboard Motor Club site, or post your question on John's Old Mercury site.
I've acquired an old Merc. What should I do to get it into good running condition?
  Digging In:  Some Tips on Evaluating and Fixing Up an Old Merc  by Bob Grubb

Perhaps you have recently acquired an old Merc, or are considering purchasing one. You may be wondering where to start to get it running again, or how to tell if it is even fixable at all.  I've put together a list of general suggestions designed to help you evaluate a motor, and give you a general idea of what could be needed to bring it into working order.

Give it a general look-over.  The ideal is a clean freshwater motor.  Beware of battered or corroded motors or motors with discolored paint on the powerhead from overheating.  Motors with broken or missing parts or battered fasteners from constant tinkering are also negative signs.
Check that the motor turns over and feels like it has decent compression(s).
Check the lower gear case for cracks or breaks.  Check the lower gear case lube.  Rusty water or no lube are very bad signs.  Crank the engine over or turn the prop, and watch the end of the prop shaft for any visible run out (bent shaft.)
If, at this point, you've not found any problems you consider serious, remove the spark plugs and check for excessive internal looseness.  I like to use an allen wrench to insert through the spark plug hole against the top of the piston.  Turn the flywheel so the piston is about mid-travel.  At this point, try moving the flywheel slightly back and forth to try to detect lost motion between the crankshaft and the piston.  Any significant movement of the flywheel without corresponding movement of the piston means disassembling the engine to find the looseness.  It can be either in the piston pin or crank pin or both.  Repeat this procedure on all cylinders.
Try moving the flywheel sideways.  There should be no noticeable looseness in this direction.  Check up and down, there should be some end play, but generally not more than .015".
Next, turn the motor over at a slow cranking pace and you should hear a soft pop from the spark plug hole each time the piston goes down and opens the intake port.  This is a necessary indication that you have crankcase compression.  Badly worn bearings, bad crankshaft seals, or leaking reed valves are causes of not having this. Another possible cause is, of course, little or no compression at all.  I find gauges vary, but generally the smallest models should have 80 pounds or more, medium size models 100 or more, and many larger models 120 lbs. or more.  Any engine with two or more cylinders should have similar compression on all cylinders.
If poor compression is your only internal problem, you may be able to restore the motor without tearing the motor down by using an engine cleaner (available from us or your local dealer.)  This can only help if the problem is caused by piston rings that are stuck from carbon deposits.
If anywhere along the line the engine has failed a test, it must be dug into to correct the problem or laid aside as a source of parts for other engines.  We are not out to ruin any equipment.  On the other hand we find it best to not unnecessarily tear down power heads.  Many times, unnecessary honing and poor cleanup results in a motor that is more "worn out" than it was before.
We recommend in general replacing the upper and lower crankshaft seals on the old Mercs, where this can be done without completely disassembling the powerhead.  
The conventional magneto or battery ignition systems used mid to late 60's and before should be capable of jumping a 1/4" spark gap in the open air.  Weaker spark than this usually means that condensers or coils or both need replacement.
Generally, fuel pumps should be rebuilt, replacing at least the diaphragm.  Carburetors usually need disassembly and cleaning to remove old gas residue and debris.
Water pump impellers should be checked by disassembly and usually will need to be replaced.
Lower gear case sealing was originally not up to today's standards and usually has only gotten much worse over time.  You should keep close tabs on the gear lube. (I check my own motors after each use.) Making these units seal as well as possible usually involves repairs to the shafts, as well as seal replacement.
Hopefully, following these guidelines will provide a good performing engine (or help you to decide that your engine is not a good candidate for restoration.)
I've become interested in old outboards in general. Where can I get some more information?
  The Old Outboard Book by Peter Hunn is the answer (part #OOB3). It's a terrific basic information source. You may also be interested in checking out the Antique Outboard Motor Club.
I've got an old Merc and my dealer can't help me keep it going. I want to work on it myself. Where do I start?
  You should start by purchasing a parts manual and service manual and possibly an owners manual for the engine. Familiarize yourself with their contents. As you determine your needs, we will try to help you from there.  You may also wish to read "Digging In:  Some Tips on Evaluating and Fixing Up an Old Merc" by Bob Grubb.
Should lead additives be used with old outboards?
  NO! Lead was never needed or desirable in any 2 cycle engine. The oil that is mixed with the gas provides all the needed lubrication.
What advice can you give for winterizing my "Old Merc"?
  There are essentially two forces your engine needs to be protected from during the off-season.  The first is cold temperatures (and the possibility of freeze damage) and the second is any possible side effects resulting from a period of disuse.  Fortunately the necessary precautions are fairly easy and straightforward.
Not everyone will have the option of storing boats and motors indoors for protection from the elements.  For the rest of us, some simple steps can help avoid damage and prolong engine life.  First, be certain no water is present in the gearcase before freezing temperatures arrive.  Not only will water left in the gearcase cause rusting, but the expansive force of freezing water is strong enough to crack gear cases.  This is a good time to change the gear lube completely (see gear lube info, above.)  

Covering boat and motor for storage outdoors is a good idea.  Shrink-wrapping probably offers the best protection for several reasons.  Its tight, taut fit won't sag and puddle water, and will shed snow and ice easily.  Rain proof vents are added to shrink wrap so that any remaining moisture can leave and the boat can "breathe."  Conventional canvas-type covers should always be removed before shrink-wrapping and stored separately in a dry place.  Mildew prevention products should be placed under the cover, according to package directions.  Any time a boat is stored out of water it should be with bow slightly elevated and drain plug out so that any moisture that finds its way in can drain out.  

Engine disuse is a second factor that can easily be prepared for.  It is recommended that fuel be stabilized with a product such as CRC Fuel Stabilizer  if the engine will not be used for one month or more.  Add stabilizer to your fuel tank according to package instructions to keep fuel fresh for next season and protect against gum & resin build-up.  Run the engine so that the product will be drawn into the engine fuel system and provide protection to the carb(s), fuel pump(s), and fuel lines.  (Remember never to run the engine without adequate cooling water supply.  Running your engine dry for even a minute can destroy your water pump and leave you vulnerable to overheating.  If you want to run your outboard in the driveway, use a flushing adapter designed for running the engine with a hose.) A storage fogging oil such as Mercury's Storage Seal should also be used during the final run of the season to protect the engine internally from rust and corrosion.  With engine running (after allowing stabilized fuel to run thru engine), disconnect fuel line from fuel tank.  Spray fogging oil into the carburetor(s) until the engine stalls.  For non-running engines, remove the spark plugs and spray into each hole, then turn the engine over several times by the starter and replace the spark plugs.

For additional rust and corrosion protection, spray the engine externally with Corrosion Guard.  Linkages and fittings can be lubricated with Mercury 2-4-C lube.  It is a good idea to remove the prop at this time and grease the propshaft with 2-4-C.

Following these simple steps will help insure that your engine lasts for many seasons to come.

Modern fuel injected outboards and inboard/outboard (sterndrives) will need additional winterizing steps.  See your dealer.
What are the implications of using gasoline with Ethanol?

Mercury Marine’s View of Ethanol
Rev. 1

Mercury Marine remains very active in developing a thorough understanding of important issues and environments in which our products must operate. Mercury’s engineers work constantly to expand our understanding of fuel technologies and their interactions with all Mercury products to ensure they perform properly and reliably. Mercury personnel work in concert with industry groups, such as the National Marine Manufacturers Association (NMMA), to offer input into the overall processes by which many decisions are made regarding fuel regulations and energy policies so future problems are minimized and future developments are beneficial to those who utilize our products. Included below is a list of questions and answers that address typical concerns of consumers.

Please feel free to contact any Mercury Marine field representative with questions, or contact us at Mercury will do its best to help find answers, whether you’re seeking general information or wishing to discuss legal proposals, or if you’re seeking information regarding ethanol tolerant

1. What are ethanol and ethanol-blended fuels?
Ethanol for fuel is highly refined beverage (grain) alcohol, approximately 200 proof, that can be produced from natural products such as corn, sugar cane and wheat. New technology will allow ethanol to be made from “cellulosic” feedstocks including corn stalks, grain straw, paper, pulp, wood chips, municipal waste, switchgrass and other sources. Ethanol used for fuel has been “denatured,” or rendered unsafe to drink by the addition of a hydrocarbon (usually gasoline). The ethanol-blended fuel E-10 refers to fuel that contains 10 percent ethanol and 90 percent gasoline. Similarly, E-85 refers to fuel that contains 85 percent ethanol and 15 percent gasoline. E-85 is intended only for engines specially designed to accept high-ethanol content fuel blends, such as the Flexible Fuel Vehicles (FFV) made by some car companies.

2. How is ethanol made?
In the U.S., ethanol is typically produced by removing the starch or sugar portion of corn and fermenting it. The fermented starch is then distilled into alcohol. Excess water is removed, resulting in very pure – 200 proof – ethyl alcohol (ethanol).
In some parts of the world, ethanol is made from a variety of raw materials. For example, sugar cane is used to produce ethanol in Brazil, while sugar beets and wheat straw are commonly used in Europe.

3. What are the characteristics of ethanol?

Ethanol is an oxygenated hydrocarbon compound that has a high octane rating and therefore is useful in increasing the octane level of unleaded gasoline. The EPA, the agency responsible for setting some of the requirements for all gasoline used in the U.S., has allowed the use of ethanol in gasoline at levels up to 10 percent as an octane enhancer and to provide beneficial clean-burning combustion characteristics that help improve some emissions.
Ethanol is hygroscopic (it has an attraction for water) and will more readily mix with water than with gasoline. It has different solvency behaviors than does gasoline, which allows it to loosen rust and debris that might lay undisturbed in fuel systems. And it can more readily remove plasticizers and resins from certain plastic materials that might not be affected by gasoline alone. Loose debris will plug filters and can interfere with engine operation. Additionally, ethanol is corrosive to some metals, especially in combination with water. Although gasoline does not conduct electricity well, ethanol has an appreciable capability to conduct electricity and therefore can promote galvanic corrosion.

4. What is MTBE and why is it being replaced?

MTBE is the chemical shorthand description for methyl tertiary-butyl ether. MTBE is another oxygenated hydrocarbon compound that has a high octane rating. It was initially a preferred compound widely used for octane enhancement as a replacement for leaded compounds in gasoline. When the EPA developed regulations requiring oxygenated gasoline to help reduce smog in several areas of the country, MTBE was the most commonly used compound to supply the additional oxygen, while ethanol was chosen for this purpose in the Midwest region of the country. Recently, most states have banned the use of MTBE because of its tendency to work its way into ground water systems, usually from leaks and spills, as an undesirable contaminant. Ethanol is being used as a replacement.

5. Does ethanol affect horsepower or fuel-efficiency?
Ethanol has a heating value of 76,000 BTU per gallon, which is approximately 30 percent less than gasoline’s heating value (which is approximately 109,000 to 119,000 BTU/gal). The result is E-10 gasoline which should yield slightly lower mileage – a decrease of approximately 3 percent. Fuels containing higher levels of ethanol will have a corresponding reduction in mileage. For example, E85 fuels produce mileage approximately 30 percent less than gasoline. The octane rating of pure ethanol (200 proof) is about 100 and is therefore useful in elevating the octane value of gasoline. In E-10 blends the presence of ethanol provides about 2.5 to 3 percent of the overall octane rating. The effect on engine horsepower is determined by the octane result of the blended fuel. Care should be taken to select fuels having the octane rating recommended for the engine as indicated in the owner’s manual for proper operation.

Compatibility with Mercury Engines

6. Are Mercury engines compatible with ethanol fuels?
The fuel-system components of Mercury engines will withstand up to 10 percent alcohol content in gasoline – the maximum level currently allowed by the EPA in the U.S. There are some efforts to establish E-20 (20 percent ethanol mixed with 80 gasoline) for use in some areas, but that will require agreement from EPA to grant a waiver. Part of the EPA waiver process will require verification from studies that demonstrate that higher levels of ethanol do not create problems with fuel-system materials or operation of hardware. E-20 has not been extensively studied by Mercury and is not acceptable for use in Mercury products. E-85 fuels must not be used in any Mercury engines and could seriously damage current Mercury products. It is not legal in the U.S. to market any ethanol fuel as gasoline if it contains more than 10 percent ethanol.

7. Will the use of fuels containing ethanol void my engine

Fuels containing up to 10 percent ethanol are considered acceptable for use in Mercury engines. Fuels containing higher levels of ethanol are not considered acceptable for use, and the use of fuels containing ethanol higher than 10 percent can void the warranty.

8. What about the fuel-system components on the boat?

It is important to follow boat manufacturers’ recommendations when selecting appropriate fuels. Use of an inappropriate fuel can result in damage to the engine and boat components that may require repair or replacement. Fuels with ethanol can attack some fuel-system components, such as tanks and lines, if they are not made from acceptable ethanol-compatible materials. This can lead to operational problems or safety issues such as clogged filters, leaks or engine damage.

9. Can ethanol-blended fuels affect the performance of two stroke

Two-stroke outboards should experience little or no decrease in performance due to gasoline fuels containing up to 10-percent ethanol when operated according to Mercury’s standard recommendations. When gasoline with ethanol is used for the first time after a fuel changeover from MTBE, the tank must be completely dry prior to introduction of gasoline with ethanol. Otherwise, phase separation could occur that could cause filter plugging or damage to the engine. If an engine is a 1990 or older model frequent inspections of all fuel-system components are advised to identify any signs of leakage, softening, hardening, swelling or corrosion. If any sign of leakage or deterioration is observed, replacement of the affected components is required before further operation.

10. How does ethanol affect my fiberglass fuel tank?

Fiberglass tanks manufactured prior to 1991 may not be compatible with gasoline containing ethanol. It has been reported that, in the presence of ethanol, some resins may be drawn out of fiberglass and carried into the engine where severe damage could occur. If an older fiberglass tank is used, check with the manufacturer to determine if gasoline with ethanol can be safely used.

11. Are older fuel lines prone to failure? What about gaskets?
During the 1980s, many rubber components for use in fuel systems were developed to withstand exposure to fuels containing ethanol. If rubber components in a fuel system are suspected to be of this vintage or older it may be advisable to replace them with newer ethanol-safe components before using fuels containing ethanol. Check with the manufacturer for advice or frequently inspect these fuel-system components for signs of swelling or deterioration and replace if problems are noted.

Recommended Practices
12. Ethanol is replacing MTBE in my region? What should I do?
Before gasoline with ethanol is introduced to your fuel tank, ask your boat manufacturer if any special precautions should be considered with the use of fuel containing ethanol. Check for the presence of water in the fuel tank. If any is found, remove all water and dry the tank completely. As a precaution, it is advisable to carry a few extra filters in case filter plugging becomes a problem during boating.

13. Should I add an additional fine-micron filter to the system to
prevent debris from entering the engine? The addition of another filter to the system will create another possible flow restriction that can starve the engine of fuel. Mercury already provides the appropriate level of filtration to protect the engine from debris.

14. How can a marina prepare for the change from MTBE to
ethanol as the fuel oxygenate?

Check with the manufacturer to make certain the tank and lines won’t experience problems with ethanol. Inspect the tank for water and, if present, pump out all water and thoroughly clean the tank. Install ethanol-compatible filters. The tank should be less than 20 percent full before adding the first load of fuel with ethanol.

15. What is phase separation, and how do I deal with it?
If significant amounts of water are present in a fuel tank with gasoline that contains ethanol, the water will be drawn into the fuel until the saturation point is reached for the three-component mixture of water + gasoline + ethanol. Beyond this level of water, phase separation could cause most of the ethanol and water to separate from the bulk fuel and drop to the bottom of the tank, leaving gasoline with a significantly reduced level of ethanol in the upper phase (see Figure 1 below). If the lower phase of water and ethanol is large enough to reach the fuel
inlet, it could be pumped directly to the engine and cause significant problems. Even if the ethanol water phase at the bottom of the tank is not drawn into the fuel inlet, the reduced ethanol level of the fuel reduces the octane rating by as much as 3 octane numbers, which could result in engine problems. The level at which phase separation can occur is determined by a number of variables, including the amount of ethanol, the composition of the fuel, the temperature of the environment and the presence of contaminants. It is very important (A) that the system is inspected for significant quantities of water in the tank before using gasoline with ethanol and (B) to limit exposure of the fuel tank to excess water. If phase separation has occurred, it is necessary to completely remove all free water from the system and replace the fuel before continuing operation. Otherwise, engine problems could occur.

Figure 1: Sample of fuel from fuel tank in which phase separation
has occurred. The upper phase is gasoline with a reduced level
of ethanol. The lower level is a mixture of ethanol and water.

16. Is an additive available that can prevent phase separation?
There is no practical additive that can prevent phase separation from occurring. The only practical solution is to keep water from accumulating in the tank in the first place.

17. Are there any additives that can allow the phase-separated
mixture to remix when added to the fuel tank?

No, the only way to avoid further problems is to remove the water, dispose of the depleted fuel, clean the tank and start with a fresh, dry load of fuel.

18. Is there a simple solution to water condensation in the tank
as a result of ethanol?

It is best to maintain a full tank of fuel when the engine is not in use. This will reduce the void space above the fuel and will reduce the flow of air in and out of the tank with changes in temperature. This will reduce condensation on the internal walls of the tank and will limit exposure of the ethanol in the fuel to humidity and condensation.

19. What should be done when storing boats with ethanol blended
fuels for extended periods?

When preparing to store a boat for extended periods of two months or more, it is best to completely remove all fuel from the tank. If it is difficult or not possible to remove the fuel, maintaining a full tank of fuel with a fuel stabilizer added to provide fuel stability and corrosion protection is recommended. A partially full tank is not recommended because the void space above the fuel allows air movement that can bring in water through condensation as the temperature cycles up and down. This condensation potentially becomes a problem. Mercury Marine Fuel System Treatment & Stabilizer can help maintain fuel systems in storage. It contains oxidation inhibitors to reduce oxidation and gum formation, metal chelating agents to protect metal components from corrosion, water absorbing agents to reduce the presence of free water, and dispersants to help suspend and disperse debris. It is best used by adding to the tank at the recommended dosage, running the engine for 10 minutes to allow the system to be cleaned, shutting off the fuel valve to interrupt the fuel supply and allow the engine to run until it stops, topping off the tank until it’s full, and capping any openings to reduce the amount of exchange with the air that might bring in condensation.

What is the proper fuel to oil ratio for my old outboard?
  The currently preferred fuel is the mid grade (89 octane). All post World War II non-racing Mercs (except KB-4's) can operate safely on a 50 to 1 fuel/oil mixture using modern TCW 3 oil. Racing models and the KB-4's should not be run leaner than 25 to 1.