By Christopher Murman,
with input from Jason Hall and Don McClymont.

Modern outboard engines are super-efficient and super-reliable in comparison to their forebears. They are lighter, smoother, more fuel-efficient and more powerful. But this has all come at a price – and we’re not talking here about money. The technical sophistication of today’s outboard engines, both two- and four-stroke, means that they need to be treated with care, especially when it comes to delving under those shiny covers. Hi-tech electronics and other wizardry have given us lots of benefits as far as modern engines go, but the flip side of the coin is that there is very little that goes on under the cowling that requires – or permits – the attention of the owner.

Nowadays, it is more a case of preventative maintenance being the best policy. Complex modern engine management, electronic ignitions and fuel injection systems are definitely not owner-friendly and should certainly not be tampered with by anyone without appropriate training or equipment.

Your outboard should be serviced annually by a manufacturer-approved dealer. The specialist will perform some sophisticated diagnostics and be able to provide a thorough analysis of your engine’s condition. He can also diagnose and remedy many subtle problems to keep the engine running smoothly. And he may be able to spot potential trouble, such as saltwater contamination or corrosion, and remedy the problem before it becomes something worse.

But, if you want to get the most out of your outboard, there are some things you, as an owner, can do that will enhance its reliability, longevity and performance. Most are simple things that owners can do to prevent the need for sometimes costly service and repairs further down the track.

An example is starting the engine when you head out for a day on the bay. Firstly, if you have a manual choke/engine warm-up lever, make sure you don’t have it wide open when you start your engine from cold. Red-lining your pride and joy on a cold start is a shortcut to needing a new set of piston rings and possibly damaging your pistons, cylinder bores and other components. Engines need to be started gently, allowing enough time for oil to circulate and reach optimum operating temperature before the throttle is used in anger.

Similarly, if you’ve been running the engine hard or for an extended period at high speed, it is generally a good idea to let it run at slow speed for at least a couple of minutes before shutting the engine down.


At start-up, it is good practice to check that the water is flowing from the engine ‘tell-tale’ fitted to most outboards. It also doesn’t hurt to check the tell-tale when underway from time-to-time, although most modern outboards are equipped with engine warning alarms that will tell you if the engine is beginning to overheat. If, at any time, you find there is no water flowing out of the tell-tale, or the alarm has sounded, shut the engine down immediately to prevent overheating and possible damage. The first thing to investigate is a blocked water intake. The intake is usually located near the bottom of the leg. Restricted or blocked water flow is frequently caused by plastic bags, seaweed or other floating debris becoming caught around the leg or in the vent. Simply raise the leg and check the intake vent. Be aware that whatever has caused the blockage may have floated off by the time the boat has slowed, so the cause may not be immediately obvious. To be on the safe side, you might want to start it again and see if the flow has been restored. If it hasn’t, there may well be a failure or blockage around the impeller that circulates the cooling water. If you’re stuck on the water, it’s better to call for a tow, rather than risk expensive engine damage by attempting to motor home.

In some instances, an engine that is being started for the first time after its last outing may have a partially blocked tell-tale resulting in sporadic, limited or no flow at all. The end of a paperclip or something similar gently probed into the outlet may dislodge the salt that has accumulated and partially blocked it. Compressed air is often the marine mechanic’s preferred course of action.

The cooling water should also exit the tell-tale in a steady flow. If it comes out in spurts, you might want to keep an eye on it and bring it to the attention of your local service centre.


The engine should always be thoroughly flushed out with fresh water after every use, ideally before it has had time to cool down completely. This is critical in the case of engines run in saltwater as it prevents the possibility of damaging salt deposits accumulating inside the engine. Accumulations of salt attract moisture, which accelerates corrosion, especially if left to sit for an extended period. Don’t free-rev the engine whilst flushing. Simply placing the ear muffs firmly and completely over the intake grills on the leg, turning the water on full and then starting the engine and leaving it to idle for a few minutes will suffice.

After each outing, and when the engine is cool, you should remove the cowling and carefully clean the engine with a wet rag, at the same time thoroughly inspecting it for anything that may be amiss. It could save you a lot of time and money in the future. The inspection should include all linkages and throttle cable connections and you should also check for water, fuel or oil leaks.

And always spray the entire powerhead, internal cowling area and the trim system with a good quality water dispersant specifically designed for marine applications. Quicksilver makes a product called Corrosion Guard, which is a Mercury-related product. Other makers of outboards have similar corrosion-inhibiting sprays. These sprays are specifically designed for this purpose and will leave a hardy protective coating when dried. It coats the powerhead and related parts with a film that is very resistant to salt (follow the directions on the label). Don’t get too carried away as the build-up can accumulate over time. Some non-marine-dedicated products may not leave this lasting film, so steer clear of anything not designed for the job.


Keep the throttle and gearbox cables in good condition by lubricating them regularly. Marine shops sell a range of products for this purpose. Some cables are self-lubricating and others are sealed, so check with the cable manufacturer before proceeding. Regularly check cable linkages to ensure they haven’t worked loose.

This happens more frequently than you might expect. Signs of loose linkages include not being able to reach full throttle, difficulty in gear-changing, whirring noises from the gearbox or an erratic engine idle.

It’s also a good idea to check the mounting of the throttle and gear control, as some throttle binnacles may not be mounted as firmly as they could be. If the throttle and gear lever moves excessively on its mounting, it can have many of the same symptoms as described above for loose linkages.

All outboards have a number of grease points to lubricate steering systems, outboard pivots and other external moving parts. These should be lubricated at least twice a year with suitable marine-grade grease. If in doubt, consult the dealer for your brand of outboard.


While many of the new outboards utilise an electronic fuel injection (EFI) system, some still use carburettors. Fuel injectors and modern carburettors are precision instruments that require the services of your local dealer to ensure they run at peak performance. The correct mixing of fuel and air is imperative for engine efficiency. Your dealer can also give you advice on suitable fuel additives to clean the fuel injectors or the carburettor, if necessary. Some of these additives also assist the fuel filters to remove contaminants.

The fuel feed from the tank should ideally have a water separating/ sediment bowl fuel filter. This filter will trap water. An automotive filter will not do. Some automotive filters have even been known to filter the oil out of the fuel. If a sight glass is fitted, check to ensure the fuel is clean and free of water and dirt before starting the engine. If required, drain the glass bowl until all of the water and sediment is removed. Ensure your mechanic changes the filter cartridge during the annual service. An engine starved of clean fuel will not deliver peak performance and may fail at a crucial moment.

If the outboard has been sitting idle for an extended period, it is a good idea to drain any remaining fuel out and replace it. The octane rating will deteriorate as fuel becomes stale, especially in a warmer climate. The fuel can form a varnish-like substance inside the injectors or carburettor, which will cause all sorts of problems with your engine. An outboard specialist recently told me of a newly-rebuilt outboard that was severely damaged after the customer used fuel that had been sitting in the tank for nine months. If your boat has a large tank capacity, only fill it up if you are going to use the entire contents within a short period of time. It is good practice to use all of the fuel within three months.

Some outboards are sensitive to either regular or high octane fuel, so seek the recommendations of the manufacturer.


If you have a small outboard, or use pre-mixed fuel, shake the tank or engine (if fitted with an internal tank) to ensure the fuel and oil is thoroughly mixed before start-up. Larger outboards with separate pre-mix fuel tanks built into the boat should get a thorough mixing while the vessel is being towed to the launch ramp.

Always mix the oil and petrol according to the manufacturer’s recommended fuel-oil ratio. Two-stroke engines that are run with insufficient oil in the fuel mix will quickly wear out or can even seize-up completely.

Many two-strokes have a separate tank for the oil, either incorporated in the cowling, in the back of the boat or both. These tanks should always be kept topped up to ensure the engine has plenty of oil available. In the case of both cowling and transom oil tank-fitted engines, only the lower, transom tank needs to be topped up. And be sure not to over-tighten the caps! They are often made out of plastic and can split. At best, this will result in a messy oil leak and, at worst, a split cap could result in oil pressure loss as some tanks need to be pressurised to work properly. It’s also a good idea to check the oil lines from the tank to the engine. They can become wedged in tight corners and become crimped, causing a reduced feed to the engine. I’d suggest carrying a spare supply of oil in the boat, too, in case you need more to get you home.

Brands and types of oil need to be considered carefully. Specific two-stroke oils are designed for specific applications, depending on whether the engine uses oil injection, high pressure injection, direct injection or whether it is a high- or low-horsepower unit. You are not saving dollars by filling the oil tank with a non-recommended, cheaper oil. At some stage, accumulated carbon deposits, lack of lubrication in critical areas and poor distribution may make you regret your dollar-driven choice of lubricant. Consult your manual or dealer if in doubt.


Many outboards, especially the larger ones, are fitted with sacrificial anode blocks. Keep the block clean with a wire brush to remove the surface corrosion and expose the clean metal. It is also important to replace the blocks when they show signs of serious corrosion and deterioration. If left unattended, they will quickly become ineffective, leaving the outboard leg susceptible to fast-acting corrosion. Replacing anode blocks is especially important if the outboard lives on a vessel that is permanently moored. If your outboard doesn’t have anode blocks fitted, it is cheap insurance to fit them. Consult your outboard manufacturer for their recommendations.

If your outboard is permanently bolted to the stern of your vessel, the transom bolts should be checked occasionally to ensure they are tight. Ideally, they should be fitted with extra locking nuts or single nylock nuts.


Any corrosion on the propeller should be carefully removed using a wire brush or scraper. Be careful not to damage the area further with deep scratches or marks.

If a propeller blade is bent, torn, chipped or has a piece broken off, get it repaired or replaced as soon as possible. Damaged blades cause additional loads and vibration on bearings, thus shortening their working life. Damaged propellers also cause cavitation, which only wastes fuel. It is not a good idea to attempt to fix damaged blades yourself, as the alloy can be very brittle and temperature-sensitive. Likewise, it is not recommended that owners attempt to remove and replace propellers, as there are some serious considerations that only a certified mechanic is equipped to deal with, such as torque settings for holding nuts, and locking mechanisms when re-tightening the nuts. Save yourself heartache and money by leaving this to the experts.


Most outboards see little use during winter months, especially in southern latitudes. If your engine is laying idle for any length of time, there are a number of preventative measures that you can take to preserve your investment. For instance, some four-stroke outboards benefit from being started, or at least rotated from time to time if the storage is prolonged to prevent valves from seizing in their guides. By rotating the engine periodically, you reduce the possibility of valves ‘hanging’ and subsequently coming into contact with pistons after several months of inactivity. If the outboard is a single-cylinder four-stroke, leave it on the compression stroke (you can tell by feeling increased resistance when rotating the engine slowly by hand). This will ensure that valves remain closed and thus will not be susceptible to hanging. This can also protect cylinder bores from the risk of corrosion.

Here are some other procedures worth performing when your boat is not in use:
• Prior to retiring your engine for the winter, flush it thoroughly with fresh water. Some outboards would also benefit from a system called “fogging”. Consult the manual or check with your local mechanic.
• Wash the outside to ensure no salt remains on any surface.
• Spray the powerhead with a good quality corrosion inhibitor.
• Disconnect the battery and ensure it is full of electrolyte and in good condition, with no corrosion on the terminals.
• Cover the engine with a lightly-oiled cloth to keep moisture at bay.
• If the engine is a smaller, portable unit, store it in the upright position in a cool, dry location, away from any sources of dust etc.
• Store it in a location where you are unlikely to accidentally kick the propeller blades, as they can do considerable damage to feet and ankles.

So, despite the complexities of modern outboards, it can be seen that owners can still play a role in looking after their engines. How you operate them, maintain them and generally look after them can have a major impact on how they look after you. Treat them well, and they’ll repay you with hours of faithful service out on the water. Misuse and abuse them and you may find they reciprocate at the most inconvenient of times.


One of the best things you can do for the welfare of your outboard is find a good manufacturer-approved dealer in your area. It is also important to find one that you like and trust. Remember, he is going to be working on your expensive outboard, so you must feel comfortable with his level of expertise. A good dealer will provide you with reliable and economical service and can also offer lots of sound advice.

If you are not happy with the service you’ve been receiving from your current outboard dealer, don’t be afraid to take your business elsewhere. Far better to get good service than to be sat out on the water stranded and wishing you’d taken the time to find a trustworthy mechanic.

Do some research; go down to the local ramp and talk to other owners with the same brand of outboard. Find out who they recommend. Also, call the manufacturer and ask for their recommendations.

Modern outboards are sophisticated pieces of engineering and represent a substantial investment on your part. It’s therefore prudent to get them serviced by a professional at least once a year or at manufacturer-recommended intervals. The dealer should have dedicated equipment to diagnose your particular brand of engine and ensure it is tuned for optimal performance. Factory-recommended dealers will also have access to technical updates and, in some cases, may be able to update your engine management system with manufacturer-released periodic upgrades.

Before we had outboards, we used oars. Don’t put yourself in a situation where you have to resort to them to get yourself back to shore, while your engine sits lifeless on the transform.