SJ23 Tech Tip D05, (Updated, 2021-11-06) Bob Schimmel


Protect the Outboard from Corrosion.

INDEX - 6in1 oil, Fogging oil, Synthetic 2-cycle oil, Mixed gasoline, Spark plugs, Anode,
Galvanic corrosion, Gear case drains, Gear case seals, Winter storage.

It is not the purpose of this web site to promote a particular manufacturer, but every once in a while a product comes along that is such an improvement over the previous that it behoves me to ignore it.  These oils simplify your end of season preparation to preserve and extend the life of your outboard.  A well maintained / running outboard is less harmful to the environment.
OMC 6 IN 1 OIL - This aerosol spray oil is designed to protect the outside of a marine outboard that is exposed to salt water spray to keep it running out on open water.  When applied, the foamy oil quickly dissipates into a liquid that spreads over the surface and creeps into tiny cracks.  After about half an hour, the oil dries to leave a tack free surface that repels water on metal, plastic, paint and ignition components.  When you spray a corroded copper connection, it leaves a nonconductive protective lubricating film.  Regular application will prevent corrosion and ignition leakage to ground.  For those of you who operate in fresh water, it will also remove an alkali deposit from the leg of an outboard.
OMC FOGGING OIL - This aerosol spray oil is designed to protect the inside of a marine outboard.  OMC retails this fogging oil that is ideal to protect the cylinder walls, pistons and rings for storing an outboard Whenever an outboard is to be stored for more than 2 months, it's a good idea to winterize the outboard... or "pickle" the cylinder wall with a fogging oil!  You simply remove the spark plugs, spray the oil directly into each cylinder, pull the starter cord a couple of times to spread the oil around and screw the plugs back in to seal the cylinders.  That's it.  Remember to keep the impeller in the water or use "earmuffs" to connect cooling water to the outboard.  It lubricates the impeller seals. 

Hot Outboard:  With the outboard hot unbolt the breather cover and spray the fogging oil into the air intake.  It's going to sound like the outboard is dying, but that's what you're trying to do.  Choke it with the fogging oil until it stalls then kill the throttle.  Remove the spark plugs when the aluminum block is cooler otherwise you risk stripping the thread.  Next, spray more fogging oil into each cylinder.  Turn the outboard over a couple of times with the pull cord (while the plugs are still out and the lower end is in water to lubricate the impeller).  Screw the plugs back into the block to seal the cylinders.  Now drain the carburetor bowl dry to prevent varnish build up.  The power head of your outboard is now winterized.  You must also drain the bottom gear oil/water mix and replace it with fresh gear oil.

First Outboard Start in Spring - At the beginning of a new boating season, fill the tank with fresh gas, then start the outboard.  The outboard should start immediately but will produce a lot of smoke till it burns off the fogging oil from the cylinder walls.  This shows you that the oil protected the inside of the outboard over winter.  Use ethanol free gas if you can find it.  In Canada Shell Gold is ethanol free.  Not sure about the U.S.


  • Both OMC 6 in 1 and Fogging Oil are retailed by Outboard Marine Corporation (OMC).   Just stop by your local Johnson/Evinrude dealer.  Other companies manufacture a similar product, but my tests demonstrate that OMC outperforms them. 
AMSOIL 2-CYCLE OIL - AMSOIL Synthetic 100:1 Pre-Mix 2-Cycle Oil (ATC) replaces mineral outboard oil that is mixed in gasoline at 50:1.  So for an outboard that requires a 50:1 mixture of mineral oil, Amsoil synthetic must be mixed at 100:1.  The pistons run cooler, the spark plugs do not foul, the outboard operates smoother and mother nature will love you for it.  While a bottle of Amsoil costs more than mineral oil, it is mixed at half the volume so your operating cost is about the same.  After one tank my 7.5HP Merc outboard ran smoother with reduced oil fumes.  Once the choke is open it produces no oil fumes.  Pretty good for a 1977 outboard that has never had an engine overhaul. 

Amsoil Synthetic 100:1 is recommended for all water-cooled and air-cooled pre-mix applications.  The manufacturer claims it reduce friction and wear, improved throttle response and delivers maximum power.  Clean-burning ash free formulation that prevents plug fouling and carbon deposits.  It delivers quick, dependable starts.  Reduces smoke and emissions and won't "load up" the outboard with oil during prolonged idling.  It provide outstanding cold temperature flow.  Contains special anti-rust agents for off-season storage.  Product Codes: AIO, ATC.

AMSOIL Saber, 100:1 Pre-Mix 2-Cycle Synthetic Oil is recommended for all pre-mix outboard applications specifying TC-W3, API TC, JASO FC and ISO EGD.  It is recommended for use with a carbureted outboard only, NOT a fuel injected outboard.  This is the oil I currently use for Panache.

AMSOIL Saber Two-Cycle Oil Mixed at 100:1

US Gallon of Gasoline

Imperial Gallon of Gasoline

1 US gal gas 1.28 oz oil 37.8 ML oil 1 Imp gallon 1.6 oz oil 45 ML oil
2.5 US gal gas 3.2 oz oil 94.6 ML oil 2.5 Imp gal gas 4 oz oil 113 ML oil
6 US gal gas 7.68 oz oil 227 ML oil 6 Imp gal gas 9.6 oz oil 272 ML oil

NOTE - After watching the local Ski-Doo racers mix their oil at very much leaner than 100:1, I started mixing Panache's outboard oil at 150:1 and have had no problems since 2010, the oil is that good.  My 1976 Merc 7.5HP outboard requires 50:1.  However, judge for yourself when mixing oil at a ratio leaner than recommended.


  • Amsoil incorporates a local representative to distribute their product.  A dealer listing is available on their web site at Amsoil

Many people premix their outboard gasoline on shore and then pour it into the tank once on board.  This makes sense because it greatly reduces the potential for a mess in the cockpit which in turn reduces the risk of polluting the water environment.  And you thought you did this for yourself! 
Did you know that gasoline mixed with oil starts deteriorating after only 45 days?  Just like diesel fuel but not as bad, the microbes thrive on the oil.  While I think it is safe to assume this process slows during freezing temperatures, I have seen enough of it in Canada to know it is still a problem here.  As the bacteria dies their carcasses settle to the bottom and accumulate into a thin gel around what appears to be a fine fibrous dandelion seed that can easily restrict the fuel filter screen of an outboard.  However, there are a couple of other problems; one of the by-products of their life cycle is water.  Being heavier than gasoline it settles to the bottom of the tank creating rust that starts to corrode the metal.  If oily gasoline is stored for a long time, varnish accumulates in the tank and carburetor.  Eventually the rust and/or varnish comes loose from the bottom and coats the fuel line, blocks the fuel filter, and plugs the jets, deteriorating outboard performance.  Fuel stabilizer helps but the best winter storage solution for the outboard is to run the carburetor dry and the best storage solution for the tank is to drain it dry.  Transfer the fuel to another container and use it in your vehicle, lawn mower or chain saw.  It is probably wise to run it through a felt filter to block any particles.  No sense moving a problem from one engine to another. 


Two Cycle Fuel (Good Info that is Applicable to an Outboard).
By Tim Ard
Forest Applications Training, Inc.

"I have been involved with two-cycle tools (chain saws) since 1974, repairing, running, testing and teaching people about and how to use them.  Fuel issues have been a major concern of two-cycle equipment manufacturers as long as I can remember.  Old gasoline, improper mixing and carburetor adjusting have cost manufacturers, equipment owners and operators a lot of trouble and money.

On a trip to Sweden and Finland around 1990 I was impressed by a product that was readily available at power equipment dealers.  The concept was a pure gasoline pre-mixed with two-cycle oil and packaged by the litre.  The fuel was focused at the emissions value to the operator and the reduced damage to the outboard and rubber parts.

A concern in many countries is the inhalation of two-cycle fumes and its long term effects on the operator and environment.  This has become evident in the USA over the past decade.  The issue I am told stems from the additives in gasoline, the age of the gasoline, along with the mix oil and the outboard efficiency.

As gasoline ages it loses its octane rating and becomes less volatile.  When this happens it burns erratically and outboard damage causing carbons and detonation occur.  The oxygenators and cleaning agents used in automotive fuels can react negatively to the efficiency of two-cycle mixed fuel.  Remember the auto fuel industry doesnít spend a lot of time making gasoline work for the two-cycle equipment user.  Pure gasoline, much like that used in the aviation industry, is more suited for the two-stroke fuel mix process.

Think about the detergents discussed in the auto gasoline advertising.  They promote detergents to clean the inside of the car engine, reducing sludge and valve deposits that can be detrimental to it.  Itís good to be scrubbing the inside of the engine, so to speak, with these agents.  However, detergents are designed to separate oil and grease from the surfaces of the block and valves.  Detergent basically lifts and separates the oil film from the metal and carries it off with the flowing oil and exhaust.  Now consider detergents, if they are doing their job, what is the effect on oil that is mixed with the gas to form your mixed two-cycle fuel.  The minute you pour in the oil and shake it up in your gasoline container an amazing scrubbing bubbles operation begins to take place.  The detergents in the gasoline are now fighting with the oil you added to separate them.  They are just doing their job.  The problem is the oil must to stay connected with the gas to do its job with the two-cycle outboard you bought.

Alcohol containing fuels add another facet to the situationÖLetís say you have your two-cycle machine adjusted and itís running good.  The fuel you had in the tank had little or no ethanol or methanol (alcohol) in it and it is running good.  Now, you run out of fuel and go buy fresh gas and mix up a fresh supply in your can.  It contains alcohol now because the new gasoline found at most pumps has 10%, or greater in some cases (Iíve heard rumour it may be even going higher, say 15%).  Your outboard rpm now runs higher and it idles differently, but you can get by.  Whatís really taking place?  If you donít re-adjust your carburetor you may be creating a lasting problem inside your now rapidly wearing outboard.  (Be very cautious of ethanol fuel.  The gas tank fuel hoses of many outboard outboards are NOT compatible with alcohol.  The rubber hose swells and will plug itself.  Long before this, the outboard will be starving for fuel.  Replace the hose with a compatible one.  Apparently most outboards prior to 2000 are affected).

You see, what I have been told, is that alcohol molecules are bigger than gasoline molecules and therefore require a larger hole to go through than gasoline molecules.  I donít drink alcohol, but those that do, say that it is the reason they drink from a glass because itís hard to drink fast and get enough from a small bottle opening.  Just kidding!  But it does make sense doesnít it- given the richer adjustment needed for alcohol content fuel flow.

Now back to the carburetor of your two-stroke.  Your carburetor mixture screw setting is open letís say two turns.  There is a given amount of fuel that is passing by the adjusting screw.  You add alcohol fuel to the situation and want it to pass by that same opening that was set for the pure gasoline.  It canít pass through at the same volume.  The outboard gets less fuel at the given setting.  The important thingÖ a two-cycle gets its lubrication from where?  The oil mixed with the gasoline.  If you limit the fuel flow, you limit the lubrication needed inside your outboard.  If you adjust the screw open more you will remain lubricated but if you donítÖ.  eventual downtime.  Potentially, the more fuel alcohol percentage in the gasoline, the greater the problem.  You can adjust to the situation but someone has to recognize the situation and do it.  The adjustment has to happen.

Consider the ethanol added to the gasoline is also sometimes a great solvent.  It affects fuel lines, seals and other rubber parts too.  It softens them and can cause all kinds of problems.  You may have seen fuel lines in your saw or trimmer that has somehow turned to chewing gum consistency.  Ethanol also collects water very well.  This can help remove moisture from gasoline but if it holds moisture in the two-cycle outboard it can cause corrosion of aluminum and magnesium components. 

I discuss carburetor adjustment in most all of my training sessions.  Sometimes I am cautioned by the organizers or supervisors at the training sessions about doing so.  They really donít want their operators adjusting.  They say, ďI donít want them to have a screwdriver nor use it.Ē  I agree with that totally.  However, I bet I hear of as many two-cycles damaged by lack of adjustment as I do adjustment.  Actually more!  If you fail to correctly adjust an outboard that is not running properly, you stand a chance of outboard damage.  An operator needs to know when a piece of equipment is out of adjustment.  This is important to the life of the outboard and operator safety.

Some people add a little extra oil to compensate for adjustment- adds a little extra lubrication - so they think.  Oil holds heat and if not burned cleanly increases harmful emissions and carbon build up.  This unburned build up and carbon inside the outboard causes bearings to skate, piston rings to stick and scoring of pistons and cylinders.

Back now to my experience from the Scandinavian trip.  The past few weeks I have been trying pre-mixed fuel from TruSouth Oil.  I think it offers a long time needed solution to several two-stroke problems and efficiencies.

 A typical scenarioÖ

While out in California on a recent training expedition I had a Husqvarna chain saw.  I was using the saw fuel from the county park service supply.  I asked how old the fuel was in their supply.  They didnít know the mix date.  I asked if they have had any fuel problems show up, they replied not that they knew of.  I then asked if they had any saws with cylinder replacements in the past few months.  They replied two in the past year.  Conversations turned to the fact they have problems with seasonal help and mixing fuel properly.  A common cause that many experience.

 I had to adjust the saw when I first started work and luckily everything ran OK with their fuel.  However, you just donít know the lubrication you are getting until some time passes.  I ran the mix for three tanks with no problems.

 I started the third class out with 50Fuel.  I had to re-adjust the idle and high speed settings a little leaner.  That told me that the fuel from the county possibly had some alcohol in the mix, not so much that it couldnít be adjusted out but the other negatives were still in place.  Adjustments have to be made if fuel isnít consistent, elevation changes and as wear occurs in the outboard.

The greatest thing is the 50Fuel ran great for the rest of the week and I know what it has in it.  A very reassuring thought!

TruSouth Oilís 50Fuel is going to answer many questionable two-cycle equipment issues.  Some of the cost effectiveness of the purchase price will be realized in less repair costs over time, stabilized running efficiency and the following:

          No mixing mistakes.

         No ethanol concerns.

         No gas cans Ė Quart bottle convenience.  Less fuel waste.

         Two year shelf life once opened and up to five year life in the case.

         No fuel related issues with dissolving plastic and rubber parts.

         Consistent carburetor adjustment and tank vapour pressure.

         Less emission fumes.

         Less can and supply storage space.

Give 50Fuel a try and you weigh out the cost advantages.  Check out their website or visit our eStore to get your supply."

If you have any questions or comments contact Tim Ard at

AVIATION GAS - (80/87 or 100/130) - Aviation gas does not contain ethanol for several reasons:

  1. Ethanol makes the fuel vaporize at altitude and causes the outboard to die.  Not always, but way too often.
  2. Ethanol swells the 'O" rings and gaskets in an outboard designed for avgas (no ethanol) and has caused numerous crashes or sudden loss of full power on takeoff.  Similarly for an outboard that was not built to burn gasoline with ethanol.
  3. Ethanol in gasoline corrodes the fuel delivery components of an outboard because it attracts water and oxygen form the atmosphere.
  4. Aircraft that have an STC (Supplemental Type Certificate) to use automotive gasoline must test their fuel for the presence of alcohol prior to refuelling.  Here is how it is done:
    (A test tube is filled about 20% with water and the level is carefully marked on the glass.  The test tube is filled nearly full with the gasoline to be tested and vigorously shaken to mix the gas and water.  The test tube is then allowed to sit for a minimum of 30 minutes undisturbed.  Then, without disturbing the test tube, the water level is checked against the mark and if the level has risen, there is alcohol present in the fuel.  The alcohol, if present, will bind with the water and raise the level.  That fuel cannot be used in an aircraft and isn't good for any outboard you value).
  5. NOTE - Aviation fuel is sold only to aircraft. 
  6. Does ethanol cause corrosion?
  7. You are better off to burn ethanol free automotive gasoline during the season and drain off all fuel for end of season storage.


SPARK PLUGS - You can tell a lot about the internal condition of your outboard by looking at your spark plugs.  Monitor the look and smell of the exhaust, the cooling water, and the sound of the outboard while underway.  It is the best everyday barometer of an outboard The state of your spark plugs is very revealing. 
  • Oily Plugs, 4 stroke - If the plugs are wet it means oil is entering the combustion chamber.  The blow by could be due to worn piston rings, valve seats or the head gasket.  It could also be faulty ignition timing.  An oily plug is something to head.
  • Oily Plugs, 2 stroke - If the plugs are wet it means the fuel mixture contains too much oil.  Correct the oil mixture to the type of oil used.
  • Burned, pitted plugs - If the insulator tip is grey and you see other signs of heat deformation the outboard is running too hot. The fuel mixture is likely too lean.  Also check the cooling system for adequate water flow and the thermostat if the outboard has one.
  • Normal plugs - If the plugs you remove are dry, free from carbon deposits, the insulator tip is slightly brown and there is very little pitting of the electrodes, you outboard is running well.
  • Remove plugs - Wait for the block to cool before removing a spark plug.  If you remove it from a hot block you are likely to strip the thread from the block. 
  • Record the sound your outboard for later playback to compare it to the current sound of your outboard.
SACRIFICIAL ANODE - The purpose of a sacrificial anode on an outboard is to protect the aluminum case from corrosion if the leg is left immersed.  Corrosion is worse in salt water than fresh.  For a boat that is left floating for a season or year round, the anode should be inspected annually and replaced when pitted.  This is when the anode can no longer provide protection.  Take note of how of quickly it deteriorates as it determines your maintenance schedule. 

In the 1970s a zinc anode was usually installed on top of the cavitation plate to leave the bottom smooth for the prop wash.  But today there are lots of different streamlined configurations unique to each outboard design.  The anode of choice for salt & fresh water is Navalloy.  It contains indium and does not form an oxide coating over itself.  If you operate purely in fresh water then Magnesium is the best choice.  Either of these are far superior to a zinc anode that stops working when it coats over in fresh water, insulating itself.  You may as well swap out that useless zinc right now. 

GALVANIC CORROSION due to DISSIMILAR METALS (2019) - At the time of this writing, Panache's Merc 75 shown below is 45 years old.  I needed to remove the plastic shift lever (starboard or opposite side) which required me to spin off the stainless steel acorn nut.  With almost no effort the nut came off; shearing the aluminum stud the nut was tightened on.  Stuff like this really makes my day!  After taking a closer look at the back of the nut, now full of useless aluminum, I realized this problem was 45 years in the making.  The aluminum shaft (the threaded end now inside the nut) and stainless steel nut are both exposed to weather.  This is a prime example of galvanic corrosion.  (Maybe that cloth outboard cover was good for something after all).  That SS acorn nut should have been removed years ago and the aluminum thread greased to prevent this problem.

Solution - Finding parts for this outboard is getting more difficult with each passing year.  So to restore the shift lever I filed the end of the shaft flat, center punched it, drilled a hole down the center and tapped it for a 6/32" SS screw.  Along with a new washer, it holds the shift lever quite nicely.  Yes I greased the screw.

GEAR CASE FILL/DRAIN PLUGS (2019) - Some outboards always have milky gear oil (due to water contamination) at the end of a season, even with new gaskets on the fill and drain plugs.  My Merc 75 had this problem for the past 30 years or so.  The reason why manufacturers select hypoid oil in the gear case is that it mixes well with water to maintain lubrication if the gear case leaks.  Some "DIY mechanics" think this leak can be resolved by installing new fill/drain gaskets and tightening the screws so tight that you risk stripping the soft aluminum thread.  Problem is, there likely a spec of grit on the gasket seat or a surface scratch that a gasket cannot seal.

Solution - A new gasket is good but if you also wrap 2 turns of Teflon tape over the thread it creates a near perfect seal with normal tightening of the screw.  At the end of the season the gear oil in my Merc 75 was perfectly clear and has been ever since I adopted this practice.  Voila, problem finally solved, until the gear case seal failed.  (Next problem, grrrrr).

GEAR CASE SEALS (2019) - After 45 years the gear case seals of my Merc 75 started leaking, evident by the trace of oil dripping out the propeller hub (exhaust).  I suspected a faulty seal on the input or output shaft which I thought might be difficult to repair.  The bearing carrier supports the output shaft within a needle bearing plus it houses an inner O-ring and an output shaft seal that together seal the oil in the gear case.  It is an expensive repair to have these seals replaced since all small horsepower Mercury outboards require a "special tool" to remove the locking ring that retains the bearing carrier.  Unfortunately there are few shops where I live that have this tool, so I made my own as shown below.  The screw driver across is my torque bar to twist it.  The torque spec calls for the locking ring to be tightened to 85 ft lbs. which is almost achievable with this screwdriver.  Close enough!

Solution - (This repair sequence is specific to a Merc 75.  Most outboards with through the hub exhaust are similar).  Place all removed parts in a tray, noting how and where they fit.  If you are unsure, place them in the order they were removed.  Start by removing the propeller nut then slide the propeller off.  Wipe the output shaft clean.  Line up the 4 keys of the "special tool" to the corresponding detents in the locking ring.  With the tool firmly seated, twist it clockwise (left hand thread) to remove the ring.  The thread should be fully lubricated if the gear case was leaking oil, but it is a good practice to apply a dab of oil to the thread prior to this removal.  Carefully slide the bearing carrier off the output shaft.  The O-ring on the gear side of the carrier should fit snug with no nicks.  Mine was stretched ~1/8" so I replaced it.  The output shaft seal on the propeller side of the carrier should fit snug around the shaft.  Mine was just a bit loose so I replaced it as well.  The output shaft seal is press fit into the back of the bearing carrier.  With the carrier properly supported on the open jaws of a bench vice, I used a large blade screw driver as a punch to remove the worn seal.  It popped out cleanly with one tap of a hammer.  The new seal was pressed in place using the jaws of a bench vice as a bearing press.  Select a matching size socket on the end of the carrier and another socket over the seal to spread the load evenly.  The new seal slid into place perfectly straight due to the greased depression in the bearing carrier. 

All parts were cleaned and installed in reverse order of disassembly.  The gear case was filled with oil and the outboard is resting on the outboard stand with a drip pan below to confirm a leak.  After the whole winter there still isn't a leak, so it is good to go for Spring.

IMPELLER - I also replaced the impeller since it was easy to do with the lower leg off.  The impeller was showing its age with reduced coolant flow due to 2 cracked vanes.  Thankfully there was no rubber missing.  See Tech Tip D08.
  • Disconnect the fuel line and run the outboard till it is out of fuel.  This sucks the carburetor fuel bowl dry so varnish cannot build up during winter.
    (I do this at haul out time and pull the boat over the trailer with two ropes).
  • If the outboard ran smooth, assume the carburetor passages and float bowl are clean so cleaning is not required. 
    (But the bowl is easy to remove and inspect if you are curious.  Its worthwhile to do.)
  • If the fuel bowl is dirty suspect the carburetor to be dirty so cleaning is required.  (Some delicate work to do!)
  • It's a good idea to remove the needle valve and flush gas through the metering holes.  Make damn sure you set the air mixture needle back to the same position to retain the fuel mixture setting. 
    (Count the number of turns out from fully closed.)
  • Clean the fuel filter/pump on the side of the block and replace the gasket if required. 
    (This gasket MUST be air tight.)
  • Replace the squeeze bulb if the internal check valve leaks or if the bulb is hard to squeeze.
     (Consider covering it during the summer to protect it from the UV damage that can harden the bulb.)
  • Spray silicon lubricant on the water pump impeller to protect the rubber and prevent it sticking to the wall of the water pump.  Hopefully you can get at it with a long skinny tube pushed provided with the spray bottle.
  • Drain and fill the lower gear case oil before Jack Frost arrives.  (Replace the screw plug gaskets and apply two wraps of Teflon tape on the thread.)
  • Clean and gap the spark plugs.  Replace if deteriorated.
  • Spray outboard fogging oil into the spark plug hole to protect the cylinder wall, piston and rings from corrosion.  Then pull the starter cord slowly several times to spread it around. 
  • Store the outboard vertical on a stand.
     (This lets the cooling passages drain dry so it is safe to freeze in storage.)
  • Tie or secure the pull cord so the impeller seals & vanes can't be torn off when dry. 
  • Tag the outboard to state the date serviced.  (You'd be amazed at what you forget.)
BOTTOM LINE - Burn ethanol free fuel in your outboard.  Run the carburettor dry at the ramp.  Remove the old gas from the tank and burn it in your vehicle.  Add fuel stabilizer to the remaining gas to prevent rust at the bottom of the tank. 

Return to Tech Tip Index. . . . . . . . . . . . . . . Have a Question?