Care and Maintenance of Outboard Motors

Care and Maintenance of Outboard Motors

General Use and Care

Outboard motors are usually reliable and easy to use. The care and maintenance of outboard motors does not require a lot of mechanical ability or knowledge. It is mostly common sense combined with taking a few minutes to regularly check over your outboard. Once you are familiar with the outboard you will see what needs to be done to prevent corrosion and to keep it operating reliably. [boxright] Guide to To The Correct Size Of Outboard Motor For You Boat   (Click the text)[/boxright]

Some basic care such as flushing the engine’s cooling system with freshwater after use in the sea and also spraying down the exterior with freshwater after use is the minimum care required.  Also it pays to remove the engine cover and spray the outside of the engine with an anti corrosion fluid such as CRC (or the like) as engine exteriors also corrode over time.  Wipe off excess spray with a rag but maintain a protective film of corrosion protection over the engine, the exterior and all metal parts including transom clamp threads etc. This will help keep the engine in good order. Lubricate, usually by greasing, the transom pivot and oil the throttle cable and carburettor linkages regularly to save future problems.
[boxright] Tip: Tie the transom clamp handles together to stop them working loose.[/boxright]
On air cooled outboards spray the metal around the top of the motor with CRC (or the like) and with the motor at idle, spray CRC into the cooling air intake(s) so hidden areas of the motor are coated with a protective film.

The Aiqidi water cooled 2 hp outboard we sell is  also partly air cooled – if you look into the vents on the side of the cowl you can see a void where air is sucked in and around under the flywheel. With motor at idle, or even a fast idle, I suggest spraying a protective fluid such as CRC into the vents around the cowl. You can remove the cowl completely to do this if you wish but it does mean undoing several small bolts and nuts. Spray anti corrosion fluid into the vents on top of the engine cover and this will coat the outside of the water jacket and the alloy exterior of the engine.

Outboard motors combine mix of aluminium alloy, steels, stainless steels, electricity, copper wire, oxygen and seawater. All these materials, even stainless to a certain extent, can corrode or facilitate corrosion. Who in their right mind would make a machine designed to used in saltwater that is destined to corrode? It is a constant task to prevent or minimise corrosion. If you don’t do it your outboard will be a mess in a few years and junk shortly thereafter.

The gearbox oil should be checked and changed about once a year on all outboards.

Starting the Engine

I suggest you start the engine with the throttle at idle setting, or just a little above. If you start up with the throttle wide open and the outboard has a centrifugal clutch, the clutch will engage instantly which may cause a problem with the boat moving suddenly. Otherwise starting a cold engine of full throttle is almost certainly going to cause premature engine wear and possibly damage some components.

See the article on using the choke [The Choke]

To start, put one hand on the engine so there is some resistance to pull against. Pull the starting rope slowly to engage the pawl in the starter before giving it a brisk pull. Once the motor is running, accelerate slowly to engage the clutch.

Note that many engines will not start on the first or second pull of the starter rope because they have to generate sufficient electrical current to charge the capacitor with enough electrical energy so it can discharge a powerful spark. This does not apply to all engines – you will get to know yours very quickly.

Running In

After about two or three tank fulls of petrol the new engine will have freed up so wait until after some use before adjusting things like idle speed etc. The diaphragm carburettor, where fitted, works better after a period of use as the diaphragms become a little more flexible. The motor also frees up a bit with use so, up to a point, engines improve with a little age.

Also a residue of gum in the carburettor, left over from the factory test run petrol some considerable time ago, can cause rough running until it dissolves away.


95 petrol is recommended.  Engines run better have more power on better petrol. Two strokes run better also. The mechanic we use says they run cooler and cleaner and have less oiling up problems running on 95.

Two Stroke Oils are not all the same. Some are designed for engines that are air cooled and run hotter than water cooled engines.  If your engine handbooks says it can be run on 50:1 you need a superior quality oil so look for marine 2 stroke oils with a rating of TC-W3.

Use a good general purpose two stroke oil at the ratio of 40:1 (25mls oil to 1 litre of petrol) on air cooled outboards and a marine two stroke oil for water cooled outboards. Depending on the manufacturer’s specifications this is usually used at the ratio of 50:1 (20mls oil to 1 litre of petrol) in modern outboards. Check you handbook.

The oil companies all manufacture 2 stroke oils of various grades and their ‘recipes’ include a light base oil,  a heavier oil to make it more slippery, solvents to help the oil mix with petrol, additives to reduce engine wear, some dye so you can recognise the oil and petrol with it mixed in and possibly some synthetic oil products to reduce smoke and improve the fuels lubricating properties.

Read the handbook: It may just say to increase the amount of oil in the petrol initially.


2 stroke oil fuel ration table – [click link]
Here is another 2 stroke oil mix quantities chart [CLICK HERE][/boxright]


If the motor is not in use while on the boat (Such as an auxiliary motor on a trailer sailor), then I suggest you keep a cover over it, even if it is a water cooled outboard. It will help to keep the dampness out of it. On sunny days at anchor the cover and the engine cover (Where there is one) could be removed to allow the sun to dry any residual dampness.

Outboard Motor Gears

On outboards with a forwardneutralreverse gearbox, change gear with the motor at idle. The gearboxes are not synchromesh but rather slightly clunky devices that either engage or disengage the appropriate drive sprocket depending on whether it is to be forward or reverse. There is no smooth transition form go to whoa. It is either in gear or out of gear so treat the outboard motor gear box gently or you may need expensive new parts every few years.

An outboard motor clutch mechanism.

A typical outboard motor clutch mechanism.

Outboard motor gear box

Photo shows the outboard motor’s drive shaft and the two splines – one for the propeller to slide onto and the other spline that the clutch slides back and forth on. Inside the centre of the back gear you can just see the specially shaped teeth that the clutch engages with.

The power from the crankshaft of the engine is driven to the gearboxes gear via the top “pinion”. This pinion then delivers the rotational power to the two gears beneath and meshing with it.

These gears rotate in opposite directions. (The pinion and gears are rotating all the time the engine is running.)

A lever (which usually is placed on the left side of the outboard or on your remote control) operates the clutch, which is located between the gears. The clutch is on a spline so it can slide back and forth while still maintaining rotational power. The clutch is moved in the desired direction to one gear or the other. When the clutch is meshed in with one of the gears (because of its matching shape) – it rotates the propeller, which drives the boat.

If we want to shift to the other gear (reverse or forward) move the clutch to the opposite gear. When the clutch is in the middle position between the gear, your gearbox is in neutral.

The clutch is a metal device shaped to mesh in with the identically shaped ‘teeth’ on the inside of each gear cog.

The clutch slides back and forth on a metal spline, moved by a ‘U’ shaped metal fingers or prong that slides the clutch back and forth between the two gears by way of the groove around the center of the clutch.

In neutral the clutch does not touch either gear as it is between the two. Thus, if a gear change is made with the motor running fast, the transition from neutral to drive can be lumpy and noisy. A rough gear change may even damage the gears.

All gears and the clutch are immersed in gearbox oil to reduce friction.

Ignition System Comment

Outboard motors use CDI or TCI ignition systems. CDI stands for Capacitor Discharge Ignition and TCI stands for Transistor Coil Ignition or Transistor Controlled Ignition.  These are ignition systems with the electrical components sealed in what looks like an epoxy resin. They are not serviceable. The beauty of electronic ignition systems is that they are totally waterproof so getting wet does not affect their operation.

I have seen outboard motors that have been running when sunk in the sea, then a few hours later, been cleaned out and started again. The ignition system was not touched but the engines started and ran as though nothing happened.

Here is an article from ‘’: (Copied below)

Outboard Motor Care

It’s easy to keep your outboard in tip-top shape, even if you’re not a mechanic. Preventive boat motor maintenance facilitates safe boating and can keep your motor reliable for a long time.

After Every Trip

  • Flush out the engine. This doesn’t just apply to saltwater adventures, but to freshwater outings as well.
  • Start up the engine and let the water pump do the rest (practice safe boating by remembering to stay clear of the prop and make sure no one tries to shift the motor into gear).
  • While you’re flushing the motor, check the water pump to make sure it has good water flow. Carefully put your finger through the stream of water. It may be warm, but it shouldn’t be hot. If the output is not strong, you may have some debris stuck in the outflow tube. Immediately shut down the engine to prevent overheating and damage. Insert a small piece of wire into the flow tube and work it back and forth. Start the engine again and check the output. If that doesn’t solve the problem, you may need a new water pump.
  • After flushing the engine, disconnect the fuel line and allow the engine to burn all the fuel in the carburetor.
    Once you’ve finished the flushing and run the engine out of fuel, be sure to turn off the key and, if you have a battery switch, turn it off.
  • Take the engine cowling off and check for fuel or water leaks. If you find leaks, consult your safe boating mechanic.
  • Wipe everything down and spray with an anti-corrosive like WD 40 or Quick-lube. Be sure to lubricate all the moving parts, such as the shift, throttle cables, carburetor valves, etc.
  • Replace the cowling and wipe it down. Keep a canvas or plastic cover on the engine between trips.
  • Always use fresh fuel. At the end of the season, boat motor maintenance should include draining your tanks and taking the fuel to the proper recycling authority.

Regular Maintenance

  • Periodically check the fuel line for cracks and worn spots.
  • Make sure the fuel primer bulb is not cracked and is pliable.
  • Make sure the fuel-line fittings seat properly and don’t leak.
  • Check the clamps on the fuel line for rust or corrosion.
  • Check the fuel tanks for damage and corrosion.
  • Check the tank vent to make sure it aspirates properly.
  • Check regularly for water in the fuel.

Another useful link:

The link below has good basic maintenance information as well as other interesting outboard motor facts:

Oregon State University

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