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.
KEEP YOUR COOL
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
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.
LUBE IT OR LOSE IT
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.
KEEP IT CLEAN AND LEAN
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.
SHAKEN, NOT STIRRED
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
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.
DOING YOUR BLOCK
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
• 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
• If the engine is a smaller, portable unit, store it in the
upright position in a cool, dry location, away from any sources of
• 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.
GO WITH THE PROS
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.