MERCURY 25 HP EFI 25MH OUTBOARD MOTOR

Description

The Mercury 25 HP EFI 25MH outboard motor is a three cylinder, fuel injected 25 hp with a manual start, tiller steering and a 15 inch short shaft. It has a 526 cc powerhead, starts without a battery thanks to Mercury’s battery free EFI, and weighs about 157 pounds. It’s a great match for aluminum tiller boats, jon boats, utility boats and small fish and ski boats. We have it for sale new with the Mercury factory warranty and ship worldwide.

If you want real performance on a 14 to 16 foot boat without the cost and complexity of electric start, the Mercury 25 HP EFI 25MH outboard motor is well worth a look.

On this page:

• Why the Mercury 25 HP EFI 25MH outboard motor
• Boats it suits
• Features
• Specifications
• Maintenance
• Alternatives
• Price and shipping
• FAQ

Why the Mercury 25 HP EFI 25MH outboard motor

Smoothness, torque and simplicity. The three cylinder engine runs more smoothly than the two cylinder motors most brands use at this power, with less vibration and a steadier idle. The 526 cc displacement gives plenty of low end pull to put a boat smartly on plane. And electronic fuel injection gives easy starting, crisp throttle response and better fuel economy than an old carbureted 25.

The clever part is that the EFI system needs no battery. When you pull the cord, the motor generates enough power to run the fuel injection and ignition. So you get modern EFI performance with the simplicity of a pull start motor: no battery, no starter, no wiring to maintain.

Model code: 25 hp, M manual start, H tiller, no L means 15 inch short shaft, EFI fuel injection.

One thing to note: on this listing the propeller is shown as not included, as it’s often chosen to suit the boat. Tell us about your boat and we’ll help you pick the right prop, or supply one with the motor.

Boats the Mercury 25 HP EFI 25MH outboard motor suits

Measure from the top of your transom to the bottom of the hull. About 15 inches means this short shaft. About 20 inches means the 25MLH. Check your boat’s capacity plate for maximum horsepower.

• Aluminum tiller boats of 14 to 16 feet
• Jon boats and utility boats with a low transom
• Small fish and ski boats
• RIBs and larger inflatables where rated

On the water

Clip on the lanyard, put it in neutral and pull. There’s no choke to set. The three cylinder engine settles into a smooth, even idle. Shift and steer with the tiller, open the throttle and the boat gets up on plane cleanly. Full throttle is 5,000 to 6,000 rpm.

Buyer questions

“Is 157 pounds too heavy for a tiller motor?”

It’s a motor you mount and leave on the boat, not one you carry around. Most owners trailer the boat with it fitted.

“Can I add electric start later?”

It’s much simpler to buy the electric start 25EH from the start, which also includes a 15 amp charging system.

“20 or 25 hp?”

The 25 is heavier, but its three cylinder engine is smoother and stronger. On 15 to 16 foot boats with a load, it’s a noticeable step up.

Mercury 25 HP EFI 25MH outboard motor features

• Three cylinder, 526 cc four stroke
• Battery free electronic fuel injection
• Manual start, no battery needed
• Superior balance and smoothness over twin cylinder designs
• Great low end torque for quick planing
• Tiller steering with forward, neutral and reverse
• 15 inch short shaft
• Water cooled with thermostat
• Saltwater rated
• SOHC, 2 valves per cylinder
• Mercury Marine factory warranty

Mercury 25 HP EFI 25MH outboard motor specifications

For the manufacturer’s own overview of the range, see Mercury’s FourStroke outboards page. Mercury updates details between model years, so if one spec really matters to your purchase, ask us and we’ll confirm it on the exact unit we ship.

Maintaining the Mercury 25 HP EFI 25MH outboard motor

Fuel: fresh 87 octane unleaded, up to 10% ethanol.

Oil: Mercury four stroke outboard oil; check before each trip, change after the break in period and then at the intervals in the owner’s manual.

Gear case: change the lube yearly.

Cooling: check the telltale every start; flush after saltwater use.

If you’re newer to boating, the US Coast Guard boating safety site is worth a read. It’s written for US boaters, but the advice on kill cords, life jackets, fuel handling and navigation rules applies wherever you are in the world.

Why three cylinders make a difference

Most outboards in the 15 to 20 hp class use two cylinders. Mercury’s 25 and 30 hp EFI motors, including the Mercury 25 HP EFI 25MH outboard motor, use three. That matters more than you might think. With three cylinders, the power pulses overlap more evenly, so the engine runs noticeably smoother, with less vibration through the tiller and transom. It also idles more steadily, which you appreciate when trolling or creeping through a no wake zone.

The 526 cc displacement gives strong low end torque, so the boat gets up on the plane briskly without having to rev the engine hard. And because the engine isn’t working as hard at cruise, it tends to be quieter and more economical than a smaller engine pushed to its limit.

What electronic fuel injection means for you

The Mercury 25 HP EFI 25MH outboard motor uses electronic fuel injection, or EFI, instead of a carburetor. In plain terms, a small computer measures things like air temperature and engine load and injects exactly the right amount of fuel every time. You don’t need to fiddle with a choke. It starts easily whether it’s a frosty morning or a hot afternoon, it idles smoothly, and it responds cleanly when you open the throttle.

EFI is also less fussy about sitting. Carburetors have tiny jets and a fuel bowl that gum up when old fuel evaporates inside them. A sealed injection system is much more tolerant, although fresh fuel is still the best policy. And because the fuel is metered precisely, EFI motors tend to be more economical, which means more time on the water per tank.

Mercury’s small EFI engines can even start and run without a battery on manual start models: the pull of the cord generates enough power for the fuel injection system to fire. That’s a clever bit of engineering, and it means you get the benefits of EFI without having to carry a battery if you don’t want to.

Using your motor through the seasons

In spring, check the oil, fit fresh fuel, look over the fuel line and connectors for cracks, and run the engine on a flushing attachment or in a test tank before the first real trip. Look for a strong cooling stream and a smooth idle.

Through summer, the main jobs are fresh fuel, regular oil checks and rinsing after saltwater use. Keep an eye on the propeller for dings. A damaged prop costs you speed and fuel, and can cause vibration.

In autumn, before the boat is laid up, do the full storage routine: flush, change the oil and gear lube, deal with the fuel system as the owner’s manual describes, grease the moving parts and store the Mercury 25 HP EFI 25MH outboard motor somewhere dry. Twenty minutes in autumn saves hours of frustration in spring.

Paperwork, warranty and keeping records

When your Mercury 25 HP EFI 25MH outboard motor arrives, write down the serial number and keep it with your invoice. Take a photo of the serial plate on your phone too. If you ever need warranty work, a dealer will ask for both, and it makes the process much quicker. The Mercury factory warranty starts from the date of purchase, so hang on to that paperwork.

It is also worth keeping a simple log: date, engine hours if you have them, oil changes, gear lube changes, impeller replacements and anything unusual you noticed. It takes seconds after each service, and it adds real value if you ever sell the boat. Buyers pay more for an engine with a clear service history, and it helps any mechanic you work with understand the motor quickly.

Check your boat insurance as well. Many policies have specific requirements for outboard security, such as a lock on the clamps or bracket, and some ask for the serial number. Better to sort that out on day one than find out after a problem.

Why buy from us

We deal in outboard motors every day, and we would rather give you a straight answer than make a quick sale. If you are not sure the Mercury 25 HP EFI 25MH outboard motor is the right motor for your boat, message us with the make, model and length of the boat, how you use it and where you boat. We will tell you honestly whether it is a good match or whether something else would suit you better.

Every motor is packed carefully for the journey, and we keep you updated from dispatch to delivery with tracking. We ship worldwide, and we are happy to explain in advance what to expect with import duties and local taxes in your country, so there are no surprises when it arrives.

After you buy, we are still here. If you have questions about setup, break in or maintenance, just ask.

A small spares kit worth carrying

You do not need a workshop on board, but a few cheap parts turn most breakdowns into a ten minute fix. For the Mercury 25 HP EFI 25MH outboard motor, we suggest a spare spark plug and the right spanner, spare propeller hardware, a spare kill cord, a small bottle of engine oil, a couple of fuses if the motor has electrics, and a fuel line O ring or connector seal. Add some cable ties, a roll of self amalgamating tape and a basic multi tool.

Pack it all in a small dry bag, keep it in the boat, and check it every spring. Most owners never need it. The ones who do are very glad it was there.

A quick checklist before every trip

It sounds obvious, but most days that go wrong on the water start with something small that got missed at the dock. Before you head out with your Mercury 25 HP EFI 25MH outboard motor, run through this in your head:

• Enough fresh fuel for the trip, plus a sensible margin
• Engine oil checked and at the right level
• Motor mounted securely and everything tight
• Kill cord clipped to you, not left on the tiller or dash
• Cooling telltale spraying water once the engine is running
• Life jackets, a way to call for help, and a small spares kit aboard

It takes a minute or two. It is also the habit that separates relaxed boat owners from the ones waiting for a tow.

More questions we get asked

Can I install the Mercury 25 HP EFI 25MH outboard motor myself?

Many owners do, following the owner’s manual. If you are not confident with mounting, rigging or electrics, a local marine mechanic can set it up quickly, and it is money well spent.

How often does it need servicing?

Check the oil before every trip. Change the engine oil and gear lube at least once a year, or at the hour intervals in the owner’s manual, whichever comes first. Inspect the water pump impeller regularly and replace it as recommended.

What fuel should I use?

Fresh unleaded petrol of the octane rating shown in the specifications, with no more than 10% ethanol, unless it is a propane model. Old fuel is the cause of most running problems.

Can I pay in instalments?

Payment options vary by country. Contact us and we will tell you what is available for your order.

Why fuel care matters so much

If there’s one thing that decides whether an outboard starts first time or leaves you pulling and swearing at the ramp, it’s fuel. Modern petrol, especially with ethanol blended in, starts to break down within weeks. It absorbs moisture, separates and leaves gummy deposits that block the tiny passages in fuel systems.

For your Mercury 25 HP EFI 25MH outboard motor, the rules are simple. Buy fresh fuel from a busy station. Don’t store it for months in a can. Keep the tank vent closed when the boat isn’t in use. Use a fuel stabiliser if the boat will sit for more than a few weeks. And before any long lay up, deal with the fuel system as the owner’s manual describes, rather than leaving old fuel inside the engine. It’s a few minutes of effort that saves a lot of cost and frustration.

Your first run

The first hours of a new engine matter. For your Mercury 25 HP EFI 25MH outboard motor, follow the break in guidance in the owner’s manual. In broad terms: run at varied speeds, avoid long periods at full throttle, and don’t let it idle for ages either. Keep an eye on the cooling telltale and gauges, and listen for anything unusual.

After the break in period, change the engine oil and filter if fitted, and check the gear lube. From then on, just use it and service it on schedule. A well run in engine rewards you with smoother running and a longer life.

Real world setups for the Mercury 25 HP EFI 25MH outboard motor

The 16 foot tiller fishing boat

A 16 foot aluminum tiller boat with two anglers, rods and a cooler. The Mercury 25 HP EFI 25MH outboard motor planes it quickly and cruises at easy revs, and the three cylinder smoothness makes long runs to the fishing grounds much more pleasant.

The utility boat

A work skiff used around moorings or a farm dam, often loaded with gear. Strong low end torque, no battery to go flat, and a simple pull start make it an easy motor to rely on.

Setting up

At about 157 pounds, use a hoist or several helpers to mount it. Bolt or clamp it to the transom as the owner’s manual describes and fit a suitable propeller. Connect and prime the fuel, check the oil, clip on the lanyard, put it in neutral and pull. Check the telltale and follow the break in guidance.

Getting the propeller right

The propeller is the part of your Mercury 25 HP EFI 25MH outboard motor that actually turns engine power into movement, and the right one makes a big difference. The goal is simple: with your boat loaded the way you normally use it, the engine should reach the top of its recommended full throttle rpm range. If it can’t get there, the prop pitch is too high and the engine is labouring. If it goes past the top of the range, the pitch is too low and the engine is over revving.

As a rough guide, each inch of pitch changes full throttle rpm by around 150 to 200 rpm. Heavier loads and bigger boats usually want less pitch. Lighter, faster boats can take more. If you mainly carry heavy loads or tow, a lower pitch prop helps. If you run light and want top speed, a higher pitch may suit. Tell us about your boat and how you use it, and we’ll help you choose.

Alternatives to the Mercury 25 HP EFI 25MH outboard motor

25EH EFI: electric start with 15 amp charging.

20MH EFI: lighter two cylinder option.

30MHGA: more power in the same family.

See our main Mercury outboard motors category and the Mercury 30 HP section.

Mercury 25 HP EFI 25MH outboard motor for sale: price and worldwide shipping

The current price of the Mercury 25 HP EFI 25MH outboard motor is shown at the top of this page. You can add it to your cart and check out straight away, or if you’d rather talk to a person first, send us a message through our contact page and we’ll come back to you with a full delivered price to your country.

What you get

• Mercury 25 HP EFI 25MH outboard motor, new
• Owner's manual
• Mercury Marine 3 year factory warranty from the date of purchase

Propeller and fuel tank can be supplied on request to suit your boat.

Shipping worldwide

We ship to buyers all over the world. Every motor is packed securely for the journey and sent by courier, freight or sea depending on its size and where you are, with tracking from dispatch to delivery. Import duty and local taxes depend on your country, and we’re happy to explain what to expect before you pay so there are no surprises.

Buying with confidence

Have a read of our refund and return policy, see what other boat owners have said on our customer reviews page, and find out more about who we are on the about page.

Mercury 25 HP EFI 25MH outboard motor FAQ

Does the Mercury 25 HP EFI 25MH outboard motor need a battery?

No. The battery free EFI runs from the pull start.

How many cylinders?

Three.

How heavy is it?

About 157 pounds.

Is a propeller included?

Not on this listing. We’ll help you pick one.

Do you ship worldwide?

Yes. Contact us for a delivered quote.

Order your Mercury 25 HP EFI 25MH outboard motor

Three cylinder smoothness and fuel injection with no battery needed. Add the Mercury 25 HP EFI 25MH outboard motor to your cart now, or send us a question first. You can also compare it with the rest of our outboard motors for sale.