From horsepower to shaft length and tilt-angle to 2- or 4-stroke, Ali Wood highlights the different features you should consider when buying a new or used outboard

There are good deals to be had on outboard engines if you know what you’re looking for, but first, it’s worth checking if there’s still life in the old one and, if not, whether you consider buying a new or used outboard motor?

Brothers Ashley and Barnaby Isard run Ash Marine in Devon, covering everything from boat brokerage to outboard care and sales.

They sell new and used outboards, and offer servicing and refurbishment.

The main advantage of buying new is having the manufacturer’s warranty, which can be five or six years.

“If you keep your books stamped up, the maintenance and fuel issues on a new engine will be much less, even though the initial outlay is so much more,” says Barnaby.

Buying an outboard motor; a man fixing an outboard engine

Jim Lake fixing an outboard. Credit: Barnaby Isard/Ash Marine

“On a second-hand outboard, we only offer three months’ warranty on labour. However, you no longer have to pay VAT – that’s 20% off the original price – plus a further 5% discount per year of depreciation for the first 10 years; that’s the rule of thumb.”

Ash Marine has a team of engineers who service old outboards.

When a customer brings in an engine they’ll give it a courtesy look, see if it runs and take some history from the owner.

They don’t charge for this, but if the owner wishes to go ahead, Ash Marine will charge for the first hour’s labour to find out if the engine is economical to repair. If it’s not, they offer scrap value or return it.

“Often people have a sentimental attachment to their outboard,” says Barnaby. “They want to save it for a couple of hundred quid, even if the engine’s not worth that.

An outboard engine on a boat

Buying a used outboard motor: Some outboards are mounted in a purpose-made well rather than hung off the transom

“We get engines dating back to the 1960s, and though it’s difficult to get hold of parts we may have some that are interchangeable and will do our best to get the engine running.”

It tends to be the smaller engines – of around 40hp or below – that come in for refurbishment.

The main issue Ash Marine sees time and time again is stale fuel.

As with diesel which has a high bio content, petrol typically has a shelf-life of six months.

The worst thing you can do if your engine has been tucked up in the shed over winter or longer is run the bad fuel through the system.

A used outboard motor lying on a ground

Outboard engines suffer in saltwater. Flush with fresh water after each trip and be prepared to fully service over winter

“The light ends in the fuel deplete, and the engine won’t run well as it makes it harder to vaporise, so cold engines are harder to start,” says Barnaby.

“Beware of dirty fuel too, as if it goes around the engine, the parts will need to be stripped down and cleaned before fresh fuel can be pumped in.”

Ash Marine offers a winterisation service to prevent this. The engineers drain all the water and fuel and replace it with a synthetic fuel, Aspen, which is expensive but much purer and doesn’t go off for six years.

“Even with Aspen, we still recommend draining the fuel if the engine is stored for longer than two years,” adds Barnaby.

Buying a new or used outboard motor: Which type of engine?

Once you’ve decided to change or upgrade your outboard, consider what its primary purpose will be.

Will it be for cruising or short bursts to the ‘big boat’ and back? Maybe you want an auxiliary for your inboard engine, or some extra oomph for watersports and towing.

“We always ask our customers whether the outboard is for inland or coastal use and if the area’s tidal,” says Ashley Isard.

“Inland waterways are regulated by speed, so a 30ft cruiser that might have had 50hp on the coast, would only need a 10hp engine if used inland.”

A man driv ing a boat with an engine

Buying a used outboard motor: Fuel injection outboards have a computer so you can ask an engineer to check the engine hours if in doubt

Similarly, Ash says some customers trade engines because they carry excess horsepower for sports such as water-ski-ing (which requires a minimum of around 40hp) or because they were previously on a heavier boat.

In these circumstances, a less powerful, lighter engine would be more suitable.

Knowing the weight of your boat and its intended purpose is the first place to start.

Buying a new or used outboard motor: Boat size to power

Dinghies and other light boats can typically be powered by a single-cylinder outboard of just 2-3hp, increasing to around 4-6hp for a 6m RIB.

Aluminium and GRP boats of around 14ft will need a two-cylinder outboard of around 8-20hp.

Bigger still, and you’re looking at outboard engines with four to six cylinders and 75hp to 90hp. Of course, this is dependent on weight.

Continues below…

Petrol pumps at a petrol forecourt

Managing E5 and E10 petrol problems

E5 and especially E10 petrol requires much more ‘fuel husbandry’ than older, ethanol-free petrol blends, as Jake Frith has discovered

A very light catamaran, for example, might still be comfortably propelled by a 10hp outboard.

The more horsepower you require, the heavier the engine, so again, think about its usage.

For larger boats or those that enjoy daily use, the outboard will probably stay on the transom.

However, if you need to lug it to and from the boat, check it’s a comfortable weight for you to carry.

Buying a new or used outboard motor: 2-stroke engines

The choice of outboards today is vast.

At the time of writing, Ash Marine has 29 used outboards for sale on its website, ranging from a 2-stroke 2hp Mariner at £249 to a 4-stroke Yamaha at £4,449.

Until the turn of the millennium, almost all marine outboard engines were 2-strokes.

More compact and easier to service, 2-stroke engines complete a combustion cycle in two movements, making them quick to respond when you turn the throttle.

An outboard engine being serviced

If servicing your own outboard be sure you don’t invalidate the warranty

When the EU’s RCD (recreational craft directive) came into force, it became illegal for leisure users to buy a new 2-stroke outboard in the UK or EU.

Manufacturers were forced to improve design by creating better fuel economy and reducing emissions and noise pollution.

This led to the development of 4-stroke outboards, which are better for the environment and more economical but also more complex to operate and fix.

The most recent direct injection (DI) 2-stroke models such as those by Mercury and Tohatsu have radically improved from their carburettor predecessors.

They shoot a very precise amount of fuel into the combustion chamber at exactly the right time, resulting in a cleaner burn and less exhaust.

However, these new 2-stroke engines can only be bought commercially by those trading in the sector the engine is used for – for example, the RNLI, fire service, sailing schools, marine contractors and boatyards.

Second-hand 2-strokes

The good news is that 2-strokes can still be legally bought and sold second-hand, provided they were first sold new before the emissions regulations came into effect in January 2007.

Although these are becoming less common, there are still many on the second-hand market that continue to give good service.


Most outboards produced today are 4-stroke engines ranging in power from 2hp to more than 400hp.

Ash Marine says most of its customers still opt for a used 4-stroke engine over a 2-stroke because, even though it’s heavier, it’s quieter and uses less fuel.

The most well-known manufacturers of 4-stroke engines today are Honda, Mercury, Suzuki, Tohatsu and Yamaha.

Most use a fuel-injection system with one injector per cylinder, creating a fast throttle response and vast improvements in economy over older models.

An orange fuel tank on a boat

Check you have enough fuel and there are no kinks in the fuel line

Weight savings are continually being made so lighter units can deliver more power to the transoms of smaller boats than ever before.

Smaller 4-stroke engines can experience fuel-related problems, due to the smaller jets used in the carburettor which can become clogged with contaminated fuel.

If you are carrying out your own service, make sure this doesn’t invalidate the warranty, which can also be affected by using incorrect replacement parts or carrying out unauthorised modifications.

Buying a new or used outboard motor: Can you verify the usage?

Outboards use two different types of fuel systems – carburetion and fuel injection/direct injection.

A carburettor delivers fuel via carefully sized jets and orifices and combines this with air according to the opening of the throttle.

Injection systems, however, rely on electronically-controlled injectors to deliver precisely the right amount of fuel to each cylinder as demanded by the engine’s computer.


Buying a used outboard motor: There are lots of older second-hand 2-strokes still available on the leisure market

An advantage to this, if you’re buying second-hand, is that you can verify the engine hours with an engineer, just like you can the mileage on a car.

“Anything fuel-injected, you can plug into a computer, but with a carburettor there’s no way of finding out mileage,” says Ashley.

“I’ve had a customer bring an outboard into the shop claiming it had done 20 miles but when I plugged it into the computer it had done 750. If you replace the computer it zeros the hours. There are ways of cheating the system which is why it’s a good idea to get it checked out!”


Availability of spares is also something to consider when buying a second-hand outboard.

Ash advises against buying Evinrude engines which were discontinued in 2020 after the manufacturer, BRP, was impacted by Covid-19.

“Parts are really hard to come by now,” he says.

Buying a new or used outboard motor: Shaft length

There are other considerations too when buying an outboard, whether new or used.

Traditionally, outboards are available as short or long-shaft models.

The position of the prop is important as it keeps the boat stable when in motion.

If it’s too high you’ll lose efficiency from turbulent water, and if it’s too low you’ll create excess drag.

If you’re not sure which length to go for, measure your transom from top to bottom in the middle of the stern.

Your shaft length should be about two inches longer.

Tilt angle

A good range of tilt angles is useful, especially if you’re operating in shallows or launching from the beach.

Some outboards use a ratchet system and others levers, with up to six different positions. Choose a system that feels intuitive.

Ask the seller to demonstrate and try it out for yourself. Then imagine doing it on a busy waterway surrounded by other users.

If manually titling your engine is hard work, or something you’ll be doing frequently, consider opting for power tilt, which allows you to tilt the engine at the push of a button.

Manual/electric start

Pull-starting an outboard can also cause shoulder pain, not to mention a lot of stress when you’re drifting in currents and winds!

Electric start offers more peace of mind, though is more readily found on models of 20hp and above.

Power thrust

In strong winds and currents, power thrust is a feature that can get your boat moving more quickly – giving 60% more thrust in reverse and 15% in forward.

Electric outboards

While electric outboards offer many advantages over petrol ones – such as low running cost, weight and environmental considerations – they’re not yet commonly available on the second-hand market so we’ve left them out for now.

Try before you buy

Given all the things that can go wrong with an outboard, Ash Marine insists on its customers understanding their engine and ensuring it’s the right one for them before they leave the premises.

“We have a test tank for engines up to 90hp. We’ll always drop the engine in and show the customer how it works,” says Barnaby. “We’d much rather show them that it runs lovely before they go out and potentially make a mistake.

“There’s a lot of user-error involved with outboards – wrong fuel, not using the kill-cord, starting it without the choke – and we have a duty of care to show customers how to use the engine properly so this doesn’t happen.” n

Thanks to Ash Marine,

Outboard engine checks from the RNLI

A drawing of a boat engine

Credit: RNLI

Before starting

  1. Ensure the engine is securely clamped or bolted to the boat.
  2. Make sure your fuel is fresh and uncontaminated, and that you have enough for your intended trip, plus a generous reserve. Do not overfill.
  3. Some 2-stroke outboards need oil mixed with their fuel while others have a separate oil reservoir. Use a marine 2-stroke oil (labelled TCW3) mixed to the right ratio. Like car engines, 4-stroke outboards have an internal oil sump. Check the level with the dip-stick, and top up if necessary with engine oil (not 2-stroke oil).
  4. Turn the steering wheel from lock to lock and the throttle/gear control from ahead to astern to make sure that the controls operate correctly.
  5. Make sure the propeller and drive leg are free of debris such as rope, weed, fishing line, plastic bags.
  6. Connect the fuel line to the tank and to the engine. Make sure it is in good condition and free of kinks.
  7. If it is fitted with a water separator/filter, inspect the filter bowl for dirt or water and drain it off if necessary.
  8. On small engines with integral tanks, make sure the fuel tap is open. Open the remote tank vent.
  9. If your engine is connected to the boat’s electrical system, make sure all the necessary switches and circuit breakers are switched on.
  10. If it is fitted with a primer bulb, squeeze the bulb until it is firm.
  11. If your engine has a kill-cord, connect it to the kill switch and clip the other end to your leg or lifejacket. Test it to see that it works.

After starting 

  • If your outboard is cooled by water, check there is a good flow of water from the cooling water tell-tale. If not, check that the tell-tale hole isn’t clogged. Note, that many smaller outboards are cooled by air, in which case this doesn’t apply.
  • Allow the engine to warm up so that it will tick over smoothly before setting off.

For outboard safety advice visit

Caring for your outboard engine

If you’re using your outboard in saltwater, be sure to flush it with fresh water after every trip to remove salt deposits from the cooling system.

This prevents corrosion and blockages. Over winter, a more thorough flush-through and service are required.

Check the manual for guidance and make sure you don’t invalidate your warranty. If in doubt, take it to a dealer.

PBO engine expert Stu Davies says: “Having taken apart many direct salt water cooled small auxiliaries, I can safely say that the deposits can range from hardly anything to almost complete blockages of the cooling channels.

“My regime on my 2.2hp Mercury 2-stroke is to take the split pin out of the prop and then slide the prop off (the engine is a direct drive and this stops us having a spinning prop in the bucket). A bucket of fresh water can then be slid onto the bare leg and the engine started and flushed.

“Also, don’t forget to drain the fuel tank and the carburettor. Just turning off the fuel tap and letting it run until it stops doesn’t cut it. The small amount of fuel left in the float chamber will still cause problems when it evaporates.”

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