MERCURY 3.5 HP 3.5MLH OUTBOARD MOTOR

Description

The Mercury 3.5 HP 3.5MLH outboard motor is the long shaft version of Mercury’s popular little 3.5. It’s built for boats with a taller transom, like small sailboats on an outboard bracket, bigger dinghies and some inflatables where a short shaft would leave the prop sucking air. We have it for sale new, with the Mercury factory warranty, and we ship it worldwide.

A lot of people land on this page after buying the wrong shaft length once already. If that’s you, don’t worry, it happens all the time. I’ll explain how to be sure the long shaft is right, what this motor is good for, and what to expect from it on the water.

On this page:

• Why the Mercury 3.5 HP 3.5MLH outboard motor
• Short vs long shaft
• Boats it fits
• As a sailboat auxiliary
• On the water
• Features
• Specifications
• Maintenance
• Alternatives
• Price and shipping
• FAQ

Why the Mercury 3.5 HP 3.5MLH outboard motor

Most tiny outboards only come with a short shaft. That’s fine for dinghies and canoes, but it leaves owners of small sailboats and taller transoms stuck. They either buy a heavier 4 or 5 hp motor they don’t really need, or they fit a short shaft and live with a prop that cavitates every time the boat pitches. The Mercury 3.5 HP 3.5MLH outboard motor solves that. You get the light, simple 3.5 with a 20 inch shaft that puts the prop down where it belongs.

It weighs about 43 pounds, just two more than the short shaft version, and it has the same balanced carry handle. It’s a single cylinder four stroke with a built in fuel tank, so there’s no separate tank or fuel line to deal with. Mercury gave the 3.5 a larger carburetor than many motors in this class, which shows up as better acceleration and more push when you need it.

Our buyers for the Mercury 3.5 HP 3.5MLH outboard motor are mostly small sailboat owners, people with larger hard dinghies, and a handful of anglers whose boats have a taller transom than usual. What they have in common is that they want something light, quiet and dependable, with the prop deep enough to actually grip the water.

Short shaft vs long shaft: how to be sure

This is the single most important decision when you buy a small outboard, so it’s worth five minutes with a tape measure.

Measure from the top of the transom, or the top of the motor bracket if you use one, straight down to the bottom of the hull or to where the water line sits when the boat is loaded. Then:

• Around 15 inches means a short shaft motor, the Mercury 3.5MH.
• Around 20 inches means a long shaft motor, this Mercury 3.5 HP 3.5MLH outboard motor.

For motor brackets on sailboats, also think about how the bracket moves. Many brackets slide up and down. With the bracket down, the anti ventilation plate on the motor should sit a few inches below the surface. If the boat pitches in a swell and the prop pops out, you need more depth, and the long shaft gives you that.

If you’re still unsure, send us a photo of your transom or bracket with a tape measure against it through our contact page. We’ll tell you which one to buy.

Boats the Mercury 3.5 HP 3.5MLH outboard motor fits

• Small sailboats and day sailers with an outboard bracket
• Trailer sailers in the smaller size range, for calm water use
• Larger hard dinghies and tenders with a 20 inch transom
• Some inflatables and RIBs with a long shaft transom
• Small workboats and punts with a taller stern

As with any 3.5 hp motor, don’t expect planing speeds on anything but the lightest boats. The Mercury 3.5 HP 3.5MLH outboard motor is a displacement speed motor. It’ll get you in and out of harbour, across a bay, and home when the wind drops. For heavier boats or more speed, consider the 4MLH, the 6MLH or the 5MLHA Sail Power.

The Mercury 3.5 HP 3.5MLH outboard motor as a sailboat auxiliary

For a small sailboat, the motor’s job is simple. Get you out of the marina, hold you head to wind while you hoist sails, and bring you home if the wind dies. You don’t need a lot of horsepower for that on a light boat. You need reliability and a prop that stays in the water.

The Mercury 3.5 HP 3.5MLH outboard motor does that job well on small, light sailboats. It’s easy to lift onto and off a bracket, which matters if you like to remove the motor while sailing to cut drag, or take it home at the end of the weekend. The built in tank means one less thing to find a home for in a small cockpit.

A few points to bear in mind. The 3.5 has forward and neutral only, with no reverse gear. On a bracket, you’ll usually get reverse by rotating the motor 180 degrees, which is fine on a small boat but takes some practice in a tight marina. If your bracket or transom makes rotating awkward, or your boat is on the heavier side, look at a motor with a proper reverse gear like the 4 hp or the 5 hp Sail Power models. Being honest about that now saves you a stressful docking later.

Also consider the conditions. In a sheltered lake or bay, a 3.5 is plenty for a small day sailer. On open water with a sea running, you’ll want more power in reserve.

Running the Mercury 3.5 HP 3.5MLH outboard motor

Starting

Open the fuel cap vent and fuel tap, set the choke if cold, and pull. It usually starts in a couple of pulls from cold and first pull when warm. Clip the stop switch lanyard to yourself before you start. On a sailboat especially, where you might be moving about the cockpit, that lanyard matters.

Steering

Twist grip throttle with a friction adjuster and a steering tension feature. On a sailboat you’ll often lock the motor straight and steer with the rudder, which is easy to do.

Noise and exhaust

Exhaust goes out below the waterline. The Mercury 3.5 HP 3.5MLH outboard motor is quiet at low throttle and doesn’t blow fumes into the cockpit the way an old two stroke would.

Speed

I won’t give you a speed figure, because it depends entirely on your hull and load. What I can tell you is that full throttle sits at 5,000 to 6,000 rpm, and on a suitable light boat the motor gets there comfortably.

Mercury 3.5 HP 3.5MLH outboard motor features

• 20 inch long shaft
• Compact and lightweight, about 43 lb
• Larger carburetor for better performance
• Digital CD ignition
• High grade marine alloy construction
• Stainless steel water pump housing
• Zinc coated water passages
• Rated for saltwater use
• Sacrificial zinc anodes
• Forward and neutral gear shift
• 360 degree steering with tension feature
• Twist grip throttle with tension control
• Integrated carry handle
• Thermostat controlled water cooling
• Visual oil level indicator
• Over rev protection
• 4 trim positions
• Below the water exhaust
• 1.0 litre integral fuel tank
• Safety lanyard stop switch
• Owner’s manual
• Mercury Marine 3 year warranty

Mercury 3.5 HP 3.5MLH outboard motor specifications

To see how this fits into Mercury’s wider range, have a look at the manufacturer’s FourStroke outboard lineup. If you need a specific detail confirmed for the unit you’re buying, just ask.

Looking after the Mercury 3.5 HP 3.5MLH outboard motor

Fuel

Fresh 87 octane unleaded, no more than 10% ethanol. Small carburetors hate old fuel. If the Mercury 3.5 HP 3.5MLH outboard motor will sit unused for more than a few weeks, shut off the fuel and run it until it stops so the carb bowl is empty.

Oil

Around 300 ml of 10W-30. Check the level window before each outing. Change after the first 20 hours, then every season or 100 hours.

On a bracket at sea

If the motor stays on a sailboat bracket, tilt it clear of the water when not in use. Rinse it with fresh water when you can. Check the anode each season. Cover the powerhead if it’s exposed to spray and sun for long periods.

Carrying and laying down

Carry it by the handle, upright. If it has to lie down, use the side the owner’s manual shows. The wrong side can let oil into the cylinder.

Gear case

Change the gear oil yearly and look at the colour. Milky oil means water ingress, which is worth fixing quickly.

For general small boat safety, the US Coast Guard boating safety site is a solid, practical read wherever you’re based.

Installing the Mercury 3.5 HP 3.5MLH outboard motor on a bracket

Set the bracket to its lowest position. Lift the motor on by the carry handle, centre it, and tighten both clamp screws firmly by hand. Tie a safety line from the motor to a strong fitting. Raise the bracket and check that the motor clears the water fully when stowed and doesn’t hit anything when you steer it through its range.

Lower the bracket again and check where the anti ventilation plate sits. You want it below the surface with the boat at rest and loaded normally. If it’s right at the surface, you may need to adjust the bracket or use the lowest setting. With the long shaft Mercury 3.5 HP 3.5MLH outboard motor, most small sailboat brackets end up just right.

Start it in neutral, let it warm up for a minute, and check the cooling telltale is spraying water. Then take it out for a gentle first run. Vary the throttle for the first hour or two while it beds in.

Common questions from sailors

Will it push my boat into a headwind?

On a small, light sailboat in moderate conditions, yes, at a modest speed. In strong winds and short steep chop, a 3.5 will struggle, as would any motor this size. Plan your passages with that in mind, or step up in power.

Can I charge my battery from it?

No. The 3.5 has no charging option. Many small sailboat owners use a small solar panel instead, which works well with a light, simple motor like the Mercury 3.5 HP 3.5MLH outboard motor.

Will it fit in my cockpit locker?

It’s compact, so often yes. Store it on the correct side as the owner’s manual describes, and make sure the fuel tap and tank vent are closed first.

What owners tend to notice in the first season

After selling a good number of these, we hear the same few comments back from owners once they’ve had a summer with the motor.

The first is how much calmer life is with the prop at the right depth. Plenty of people who buy the Mercury 3.5 HP 3.5MLH outboard motor had been running a short shaft on a tall transom before. They were used to the motor racing every time a wave passed under the stern, then biting again with a jolt. With the long shaft, that mostly goes away. The motor just keeps pushing.

The second is the weight, or rather the lack of it. On a small sailboat, hanging a 60 or 70 pound motor off the stern changes how the boat sits and sails. At about 43 pounds, the Mercury 3.5 HP 3.5MLH outboard motor barely affects trim, and it’s much easier to lift off the bracket and into a locker when you want to sail without drag.

The third is how little it asks of you. Fresh fuel, a quick glance at the oil window, a rinse after salty days. That’s it. For a lot of sailors, the motor is something they want to forget about until they need it, and then they want it to start. This one does that.

The last comment is usually about reverse. A few owners find rotating the motor for reverse awkward on their particular bracket, especially single handed in a tight marina. If you already know your berth is tricky, that’s a sign to consider a motor with a proper reverse gear. If your mooring or berth is open and easy, it’s rarely an issue after a few practice runs.

Choosing between the 3.5MLH and a heavier long shaft motor

Here’s a simple way to think about it. Ask yourself three questions.

How heavy is the boat? If it’s a light dinghy or day sailer, the Mercury 3.5 HP 3.5MLH outboard motor is plenty. If it’s a heavier trailer sailer with a cabin, fuel, water and people aboard, you’ll probably be happier with 5 or 6 hp.

Where do you sail? Sheltered lakes, rivers and harbours suit a 3.5 perfectly. Exposed coasts with strong tides and chop call for more power in reserve.

How often do you need reverse? Occasional use is fine with a rotating motor. Frequent tight manoeuvring in a busy marina is easier with a gearbox.

If your answers are light boat, sheltered water and occasional reverse, the Mercury 3.5 HP 3.5MLH outboard motor is very hard to beat for the weight and price. If they point the other way, have a look at the long shaft 4, 5 and 6 hp motors we listed below, or just message us and we’ll help you pick.

A note on fuel for occasional users

Many sailboat auxiliaries only run for a few minutes at a time, leaving and entering harbour. That means fuel sits in the tank for a long time. Buy small amounts, keep the tank vent closed when not in use, and run the carb dry before any long lay up. It’s the easiest way to keep the motor starting on the first pull, season after season.

Security and theft

Small outboards are, sadly, a favourite target for thieves because they’re light and easy to sell on. If your Mercury 3.5 HP 3.5MLH outboard motor stays on the boat at a public mooring or marina, fit an outboard lock over the clamp screws. They’re inexpensive and they stop the casual grab. Take a photo of the serial number plate and keep it with your purchase paperwork, which also helps with any warranty claim. Some owners also engrave a postcode or boat name on the bracket and cowl. None of it is foolproof, but together it makes your motor much less appealing to anyone looking for an easy target.

When you’re leaving the boat for a long time, the safest place for a motor this light is off the boat, locked in a shed or garage. It takes a minute to lift off, and that minute can save you the cost and hassle of replacing it.

Alternatives to the Mercury 3.5 HP 3.5MLH outboard motor

Mercury 3.5MH: the same motor with a 15 inch short shaft. Choose it for dinghies, canoes and low transoms.

Mercury 4MLH: long shaft, heavier at about 58 lb, but with a proper forward, neutral and reverse gearbox, a pressurised oil system and an optional charging coil. A good step up for heavier sailboats.

Mercury 5MLHA Sail Power: designed specifically for sailboats, with a high thrust prop. If your boat is heavier or you sail in open water, it’s worth a serious look.

Mercury 2.5MH: lighter and cheaper, but short shaft only.

You’ll find all of these in our Mercury outboard motors category, including the 4 HP and 6 HP sections.

Mercury 3.5 HP 3.5MLH outboard motor for sale: price and worldwide shipping

The price of the Mercury 3.5 HP 3.5MLH outboard motor is shown at the top of this page. Buy it through the cart, or get in touch for a full delivered quote to your country.

In the box

• Mercury 3.5 HP 3.5MLH outboard motor, new
• 3 blade composite propeller, fitted
• Built in fuel tank
• Owner’s manual
• Mercury Marine 3 year factory warranty, from the date of purchase

Shipping

We ship worldwide. The motor is packed securely, shipped dry without fuel, and sent by courier or freight with tracking. We’ll help you understand import duty and local taxes in your country before you pay, if you ask.

More about us

See our refund and return policy, read what our customers say, and learn more on our about page.

Mercury 3.5 HP 3.5MLH outboard motor FAQ

What’s the difference between the 3.5MLH and 3.5MH?

Only the shaft. The MLH is a 20 inch long shaft, the MH is a 15 inch short shaft. Everything else is the same.

Is the Mercury 3.5 HP 3.5MLH outboard motor new?

Yes, new, with the full Mercury factory warranty.

Does it have reverse?

No reverse gear. You turn the motor around on its swivel to go astern.

How heavy is it?

About 43 pounds.

Is it saltwater rated?

Yes. Rinse it with fresh water whenever you can.

Do you ship worldwide?

Yes. Contact us with your country for a delivered price.

Order your Mercury 3.5 HP 3.5MLH outboard motor

If your transom or bracket calls for a long shaft and you want something light and reliable, the Mercury 3.5 HP 3.5MLH outboard motor is a very good fit. Add it to your cart today, or ask us anything first. You can also browse our full range of outboard motors for sale.