MERCURY 4 HP 4MLH OUTBOARD MOTOR

Description

The Mercury 4 HP 4MLH outboard motor is a long shaft, pull start, tiller steer four stroke with a proper forward, neutral and reverse gearbox. It’s one of the most popular small auxiliaries for sailboats, and it’s just as handy on bigger dinghies, inflatables with tall transoms and small workboats. We have it for sale new, with the Mercury factory warranty, and we ship it worldwide.

If you’ve got a 20 inch transom or an outboard bracket and you need a motor that goes backwards without having to spin it round, you’re in the right place. Below is everything you need to decide whether the Mercury 4 HP 4MLH outboard motor is the one for your boat.

On this page:

• Why the Mercury 4 HP 4MLH outboard motor
• Is long shaft right for you?
• As a sailboat auxiliary
• Other boats it suits
• On the water
• Features
• Specifications
• Maintenance
• Buyer questions
• Alternatives
• Price and shipping
• FAQ

Why the Mercury 4 HP 4MLH outboard motor

Because it combines three things that are hard to find together at this size: a long shaft, a real reverse gear, and a weight you can still manage on your own. At about 58 pounds, the Mercury 4 HP 4MLH outboard motor isn’t featherweight, but it has a good carry handle and most adults can lift it onto a bracket without help.

Inside, it’s a 123 cc single cylinder four stroke with a pressurised wet sump oil system and a low oil pressure warning. That’s a step up from the splash lubrication on the 2.5 and 3.5, and it’s one reason this motor holds up well to the long, steady, low rpm running that sailboat auxiliaries often do.

It also has a built in fuel tank, plus a standard connection for an external tank. For short hops in and out of harbour, the internal tank is plenty. For a longer motor on a calm day, plug in a portable tank and forget about fuel.

We sell the Mercury 4 HP 4MLH outboard motor mostly to small sailboat owners, but also to people with larger dinghies, RIBs with a tall transom, and small river and canal boats. The common thread is a tall stern and a need for reliable reverse.

Is a long shaft right for your boat?

Measure from the top of the transom or bracket, straight down to the bottom of the hull. Around 20 inches means long shaft, and the 4MLH is right. Around 15 inches means short shaft, and you want the Mercury 4MH instead.

On a sailboat bracket, it’s also about how the boat moves. The anti ventilation plate should sit a few inches under the water with the bracket down and the boat loaded. When the stern lifts on a wave, the prop still needs to be in solid water. If you’ve had problems with a short shaft motor racing and cavitating in any sort of swell, a long shaft usually solves it.

Not sure? Send us a photo of your transom or bracket with a tape measure through the contact page and we’ll tell you.

The Mercury 4 HP 4MLH outboard motor as a sailboat auxiliary

For small to mid size day sailers and light trailer sailers, 4 hp is a comfortable amount of power. It’s enough to motor out of a marina, hold the bow into the wind while you raise the main, and get home at a sensible pace when the breeze dies. It isn’t so heavy that it drags the stern down or upsets the trim when you’re sailing.

The reverse gear is the big win over smaller motors. Backing out of a berth, stopping the boat as you come alongside, or reversing away from a mooring buoy all become simple. You shift into reverse with the front mounted lever and add a touch of throttle. No need to spin the motor through 180 degrees while also steering the boat.

The shallow water drive also helps sailors who use shallow anchorages or beaches. Lock the Mercury 4 HP 4MLH outboard motor in a raised position and you can creep in over the shallows at low speed with less risk of hitting the bottom.

For heavier sailboats, or if you want a propeller specifically designed for pushing displacement hulls, look at the Mercury 5MLHA Sail Power as well. Its high thrust setup suits heavier boats very well.

Other boats the Mercury 4 HP 4MLH outboard motor suits

• Larger hard dinghies and tenders with a 20 inch transom
• Inflatables and RIBs built for a long shaft motor
• Small workboats and punts
• Canal and river boats with a higher stern
• Small aluminum boats with a long shaft transom

On most of these boats, the Mercury 4 HP 4MLH outboard motor gives a relaxed displacement cruise rather than planing. That’s perfect for sheltered water, slow rivers and canals where speed limits are low anyway.

Running the Mercury 4 HP 4MLH outboard motor

Starting

Open the fuel vent and tap, set the choke when cold, put it in neutral and pull. Start in gear protection stops it starting in forward or reverse. Clip the safety lanyard to yourself first. On a sailboat, where you’re moving around the cockpit, that’s especially important.

Shifting and steering

The shift lever sits at the front of the motor. Shift at idle, deliberately. Steering tension is adjustable, so you can lock the motor straight and steer with the rudder, or leave it free to steer with the tiller. Most sailors lock it straight once they’re out in open water.

Throttle

Twist grip with a friction adjuster. Set a cruise speed and let go.

Exhaust and noise

Through the prop hub exhaust keeps the noise down and the fumes underwater, well away from the cockpit.

RPM and speed

Full throttle runs from 4,500 to 5,500 rpm. Speed depends on the hull, weight and conditions, so I won’t quote a figure that won’t match your boat.

Mercury 4 HP 4MLH outboard motor features

• 20 inch long shaft
• Digital CD ignition with spark advance
• High grade marine alloy construction
• Stainless steel water pump housing
• Zinc coated water passages
• Rated for saltwater use
• Sacrificial zinc anodes
• Forward, neutral and reverse gear shift
• Forward mounted gear shift selector
• Adjustable steering tension control
• Twist grip throttle with tension control
• Integrated carry handle
• Thermostat controlled water cooling
• Shallow water drive with 6 trim positions
• Quiet through propeller hub exhaust
• 1.15 litre integral fuel tank with external tank connection
• Start in gear protection
• Low oil pressure warning indicator
• ESG over rev protection
• Safety lanyard stop switch
• Owner’s manual
• Mercury Marine 3 year warranty

Mercury 4 HP 4MLH outboard motor specifications

Mercury’s own FourStroke outboards page gives an overview of the full range. If a particular spec matters to you, ask and we’ll confirm it for the unit you’re buying.

Charging a small battery

Many sailors want to keep a small battery charged for navigation lights, a VHF or an instrument or two. The Mercury 4 HP 4MLH outboard motor doesn’t charge as standard, but an optional 12 volt, 50 watt charging coil can be fitted. It’s modest, so treat it as a top up rather than your main power source. Pair it with a small solar panel and most small boats are well covered. Ask us about the kit when you order.

Maintaining the Mercury 4 HP 4MLH outboard motor

Fuel

Fresh 87 octane unleaded, up to 10% ethanol. Sailboat auxiliaries often run only a few minutes at a time, so fuel sits for long periods. Buy small amounts. Before any lay up of more than a few weeks, shut off the fuel and let the Mercury 4 HP 4MLH outboard motor run until it stops.

Oil

About 450 ml of 10W-30. Check the dipstick before you head out. Change after the first 20 hours, then every 100 hours or yearly.

Gear case

Change the gear lube every year. Milky lube means a seal needs attention.

On the bracket

When sailing, tilt the motor fully up or lift the bracket so the lower unit is out of the water. That cuts drag and stops weed and barnacles growing on it. Rinse it with fresh water when you can and check the anode each season.

Carrying and stowing

Carry it upright by the handle. If you lay it down, use the side shown in the owner’s manual.

For general boating safety, the US Coast Guard boating safety site covers the essentials clearly, and most of it applies anywhere in the world.

Installing it on your boat

Lower the bracket, lift the motor on by the handle and centre it. Tighten both clamp screws firmly by hand, then tie a safety line from the motor to a strong fitting. Raise and lower the bracket to check the motor clears everything, including the rudder, through its full steering range.

Check the oil, add fresh fuel, clip on the lanyard, and start it in neutral. Let it warm up and look for the cooling telltale stream. Go for a gentle first run, varying the throttle for the first hour or two.

Buyer questions about the Mercury 4 HP 4MLH outboard motor

“Will 4 hp push my trailer sailer?”

For light trailer sailers in sheltered water, generally yes. For heavier boats, or exposed waters with strong tides and wind, you may want 5 or 6 hp. Tell us the boat’s length and approximate weight and we’ll give you an honest recommendation.

“How far will it go on a tank?”

The built in tank is small, just over a litre, so it’s best for short motoring. For longer runs, connect an external tank. The Mercury 4 HP 4MLH outboard motor uses very little fuel at a moderate throttle, so even a small portable tank gives you a lot of range.

“Is it heavy to lift onto a bracket?”

At about 58 pounds, it’s manageable for most adults, especially using the balanced carry handle. If lifting it single handed over the stern rail feels awkward, a second person or a simple lifting strap makes it easy.

“What’s the best way to stop theft?”

Fit an outboard lock over the clamp screws, record the serial number, and take the motor home when you leave the boat for long periods. Small outboards are popular with thieves, so a few precautions go a long way.

Off season storage

Flush the Mercury 4 HP 4MLH outboard motor with fresh water. Run the carburetor dry. Change the engine oil and gear lube. Grease the swivel and clamp screws. Store it upright or on its correct side somewhere dry. In spring, fresh fuel and a quick oil check are all it needs.

What sailors tell us after a season with the Mercury 4 HP 4MLH outboard motor

We keep in touch with a lot of our buyers, and sailboat owners in particular tend to send us their thoughts once they’ve had a full season with the motor. A few themes come up again and again.

The most common comment is about docking. Owners who moved from a small motor without a gearbox say the reverse gear on the Mercury 4 HP 4MLH outboard motor changed how they feel about coming back to the marina. Instead of dreading the last fifty metres, they can slow the boat, stop it and back it into place with far more control. One owner who sails single handed said it was the best money he’d spent on the boat.

The second comment is about reliability. Sailboat auxiliaries have a tough life. They sit for days or weeks, then they’re expected to start immediately when the wind drops or the tide turns. The owners who follow the simple fuel routine, buying small amounts and running the carb dry before a long break, tell us the motor starts in a pull or two every time.

Third is noise. People are pleasantly surprised by how quiet the motor is at the low throttle settings used for motoring in harbours and anchorages. The exhaust goes out through the prop hub, under the water, so there’s no rasping exhaust note and no fumes in the cockpit.

The last comment is honest feedback about weight. At around 58 pounds, some owners with high stern rails find lifting the motor on and off the bracket awkward on their own. A few have fitted a small block and tackle or a davit to make it easier. If you plan to remove the motor every time you sail, think about how you’ll do that before you buy.

Getting the best from the Mercury 4 HP 4MLH outboard motor on a sailboat

A few small things make a big difference to how well a small outboard works on a sailing boat.

Bracket height. Set up the bracket so the anti ventilation plate sits several inches underwater with the boat loaded as you’d normally sail. Too high and the prop will race in a swell. Too low and you add drag and risk the powerhead getting wet in a following sea.

Trim angle. Use the tilt pin to get the motor running as close to vertical as possible when the boat is at rest. That gives the most efficient thrust. With six positions on the Mercury 4 HP 4MLH outboard motor, it’s easy to find the right one.

Steering. Most sailors lock the outboard straight with the steering tension and steer with the rudder. It gives a much steadier course than steering with the motor alone, and your hands are free for lines.

Fuel. Keep a small external tank in a cockpit locker for longer motoring days. It’s easier and safer than topping up the built in tank at sea.

Kill cord. Always wear the lanyard. On a sailboat you’re often moving around, and a motor that keeps running after someone goes overboard is a real danger.

Get those right and the Mercury 4 HP 4MLH outboard motor becomes something you barely think about, which is exactly what you want from an auxiliary.

Spares worth keeping aboard

You don’t need a full workshop, but a small bag of spares turns most breakdowns into a ten minute fix instead of a tow. For the Mercury 4 HP 4MLH outboard motor we suggest a spare spark plug and a plug spanner, a spare shear pin or prop hardware, a spare fuel line clip and O ring if you run an external tank, a small bottle of engine oil, and a spare safety lanyard. Many owners also keep a water pump impeller at home so it can be swapped at the start of each season if needed. Add a roll of self amalgamating tape and a few cable ties and you’re covered for almost everything that can go wrong on a small outboard away from the dock.

Keep them in a dry, sealed bag in a cockpit locker, and check the bag every spring. It’s a small thing, but it’s the kind of preparation that makes a day on the water relaxed rather than stressful.

Alternatives to the Mercury 4 HP 4MLH outboard motor

Mercury 4MH: the same motor with a 15 inch short shaft. Best for dinghies and small fishing boats with low transoms.

Mercury 3.5MLH: lighter at about 43 lb, long shaft, but no reverse gear and less torque. Good for very light sailboats.

Mercury 5MLHA Sail Power: built for sailboats with a high thrust propeller. Ideal for heavier boats.

Mercury 6MLH: more power, still portable. A good choice for bigger trailer sailers or exposed water.

Browse them all in the Mercury 4 HP section and the main Mercury outboard motors category.

Mercury 4 HP 4MLH outboard motor for sale: price and worldwide shipping

The price of the Mercury 4 HP 4MLH outboard motor is at the top of this page. Add it to your cart, or contact us for a delivered price to your door.

What you receive

• Mercury 4 HP 4MLH outboard motor, new
• 3 blade aluminum propeller, fitted
• Built in fuel tank with external tank connection
• Owner’s manual
• Mercury Marine 3 year factory warranty from the date of purchase

Shipping

We ship worldwide, securely packed and dry, by courier or freight with tracking. Import duty and taxes depend on your country, and we’ll explain what to expect before you pay if you ask.

About buying from us

See our refund and return policy, read customer reviews, and learn more on the about page.

Mercury 4 HP 4MLH outboard motor FAQ

Does the Mercury 4 HP 4MLH outboard motor have reverse?

Yes, a full forward, neutral and reverse gearbox.

What shaft length is it?

20 inches, a long shaft.

How much does it weigh?

About 58 pounds.

Can it use an external fuel tank?

Yes, the external tank connection is standard.

Is it saltwater rated?

Yes. Rinse it with fresh water when you can.

Is it new?

Yes, brand new with the Mercury factory warranty.

Do you ship to my country?

We ship worldwide. Contact us for a delivered quote.

Order your Mercury 4 HP 4MLH outboard motor

Long shaft, real reverse, solid lubrication and a weight you can handle. For a small sailboat or a tall transom boat, the Mercury 4 HP 4MLH outboard motor is one of the most sensible choices you can make. Add it to your cart now, or send us a question. You can also browse all our outboard motors for sale.