MERCURY 5 HP 5MLH-LPG PROPANE OUTBOARD MOTOR

Description

The Mercury 5 HP 5MLH-LPG propane outboard motor is a 20 inch long shaft, pull start four stroke that runs on propane instead of gasoline. It’s made for boats with a taller transom, like sailboats on an outboard bracket, larger dinghies and some inflatables, where you want the convenience of propane and a prop that stays deep in the water. We have it for sale new, with the Mercury factory warranty, and we ship it worldwide.

If you’ve landed here, you probably already know you need a long shaft. You might also be tired of stale gasoline ruining a small carburetor every winter. This motor fixes both problems at once. Here’s how it works and whether it suits your boat.

On this page:

• Why the Mercury 5 HP 5MLH-LPG propane outboard motor
• What the model code means
• Boats it suits
• On a sailboat
• Running it
• Features
• Specifications
• Maintenance and propane safety
• Other options
• Price and shipping
• FAQ

Why the Mercury 5 HP 5MLH-LPG propane outboard motor

Small outboards on sailboats and occasional use boats have a hard life, and it isn’t the running that hurts them. It’s the sitting. A motor that runs for ten minutes leaving the marina and ten minutes coming back, then sits for two weeks, is the perfect recipe for stale fuel. Gasoline breaks down, especially with ethanol in it, and leaves gum and varnish in the tiny jets of a small carburetor. Then one day it won’t start when you need it.

The Mercury 5 HP 5MLH-LPG propane outboard motor doesn’t have a carburetor full of gasoline to spoil. It runs on propane from an external cylinder, and propane doesn’t go stale. You can leave it for weeks or months, connect the gas and it starts. On a sailboat, where the motor is your safety net when the wind drops or you need to get off a lee shore, that reliability matters a lot.

Underneath, it’s Mercury’s proven 5 hp, 123 cc single cylinder four stroke with forward, neutral and reverse, shallow water drive and start in gear protection. You get the long shaft and the propane system in a motor weighing about 58 pounds, still light enough to lift onto a bracket by yourself.

What “5MLH-LPG” means

• 5 is the horsepower.
• M is manual start.
• L means a 20 inch long shaft.
• H is tiller handle steering.
• LPG means it runs on liquefied petroleum gas, propane.

The short shaft version is the 5MH-LPG. There’s also a sailboat specific propane model with a high thrust prop and charging, the 5MLHA-LPG Sail Power.

Boats the Mercury 5 HP 5MLH-LPG propane outboard motor suits

Measure from the top of the transom or bracket down to the bottom of the hull. About 20 inches means this long shaft motor is right. About 15 inches means you want the short shaft 5MH-LPG. About 25 inches means extra long shaft, such as the 5MXLHA-LPG.

• Small sailboats and day sailers with a transom bracket
• Light trailer sailers for sheltered water
• Larger hard dinghies and tenders with a 20 inch transom
• Inflatables and RIBs with a long shaft transom
• Small river and canal boats with a higher stern

On these boats, the Mercury 5 HP 5MLH-LPG propane outboard motor gives a comfortable displacement cruise, with reverse for docking and plenty of control at low speed.

The Mercury 5 HP 5MLH-LPG propane outboard motor on a sailboat

For a small sailboat, 5 hp is a good amount of power. It gets you out of the marina and home against a moderate breeze, holds the bow up while you hoist sail, and gives you real control in reverse when docking. The long shaft keeps the prop in solid water when the stern lifts on a wave, which is a common problem with short shaft motors on sailboats.

The propane side of things suits sailboats especially well. Many sailboats already carry propane for the galley stove, so the crew is used to handling it safely. You’re not adding a second fuel to the boat, and you’re removing the risk of gasoline fumes collecting anywhere.

A few practical points. Keep the propane cylinder in a vented cockpit locker or a proper gas locker that drains overboard, never down below. Make sure the supply hose runs cleanly to the motor without chafing and without getting in the way of lines or the tiller. And if you want your motor to top up a battery, look at the 5MLHA-LPG Sail Power, which includes a charging system and a high thrust prop. This 5MLH-LPG has no alternator.

Running the Mercury 5 HP 5MLH-LPG propane outboard motor

Starting

Connect the supply line to the cylinder, open the valve, put the motor in neutral, clip on the lanyard and pull. With no carb to flood, starting is usually easy even after long breaks.

Shifting

Forward, neutral and reverse with a front mounted lever. Shift at idle, deliberately.

Steering and throttle

Adjustable steering tension, so you can lock it straight and steer with the rudder. Twist grip throttle with friction control.

Shallow water drive

Six trim positions and a locked shallow water setting help in thin water near beaches and moorings.

Noise and smell

Exhaust exits through the prop hub. Propane burns cleanly, so there’s very little smell in the cockpit.

RPM

Full throttle range is 4,500 to 5,500 rpm. Speed depends on your boat and conditions.

Mercury 5 HP 5MLH-LPG propane outboard motor features

• Runs on propane (LPG) from an external cylinder
• 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
• 8 inch pitch aluminum propeller
• 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 5 HP 5MLH-LPG propane outboard motor specifications

Mercury’s FourStroke outboards page gives a good overview of their range. Ask us if you need anything confirmed for the specific unit.

Maintenance and propane safety

Propane system

Check the hose and fittings before every use for cracks, chafe or damage. Keep the connector clean. Close the cylinder valve when you’re finished. Store cylinders upright, secured, and in a ventilated space where any leak can escape, never below decks.

Engine oil

About 450 ml of 10W-30. Check before each trip. First change at 20 hours, then every 100 hours or yearly.

Gear case

Change the gear lube yearly. Milky lube means water is getting in.

Cooling and salt

Check the telltale stream on every start. Rinse the Mercury 5 HP 5MLH-LPG propane outboard motor with fresh water when you can and keep an eye on the anodes.

On the bracket

Tilt it clear of the water when sailing to cut drag and stop marine growth.

The US Coast Guard boating safety site has good general guidance on safe boating and fuel handling that applies around the world.

Questions we get about the Mercury 5 HP 5MLH-LPG propane outboard motor

“Will propane give me the same power as gasoline?”

In normal use on a small boat, the difference is hard to notice. The Mercury 5 HP 5MLH-LPG propane outboard motor shares its powerhead with the gasoline 5 hp. Where you do notice a difference is in how it starts after sitting, and how clean it smells.

“How big a cylinder should I carry?”

That depends on how long you motor for. On a sailboat that only motors in and out of harbour, a modest refillable cylinder can last a long time. For long motoring days or a small river cruiser, carry a bigger one or a spare. Small disposable camping cylinders are fine for short trips but aren’t ideal for regular use. Tell us how you use your boat and we’ll suggest a sensible setup for the Mercury 5 HP 5MLH-LPG propane outboard motor.

“Is it safe to have propane in the cockpit?”

Handled properly, yes. Propane is heavier than air, so it must be stored where a leak drains overboard, never down below or in an unvented locker. Most sailors are already used to this from their galley stove. Check hoses and fittings each time, close the valve when finished, and follow the owner’s manual and any local rules.

“Can I use my galley propane for the motor?”

Possibly, depending on your system, but most owners keep a separate cylinder for the motor. It avoids long hose runs through the boat and means a problem with one doesn’t affect the other. We’d suggest a dedicated cylinder in a vented locker near the stern.

“What happens if I run out of propane at sea?”

The same thing that happens when you run out of gasoline: the motor stops. Carry a spare cylinder, or at least keep an eye on how much you’ve used. Many owners weigh their cylinders to check what’s left.

“Is it hard to service?”

No. It’s simpler than a gasoline motor in many ways, with no carburetor to clean. Oil, gear lube, spark plug, impeller and anodes are routine jobs any handy owner can do.

Installing it on a bracket

Lower the bracket, lift the Mercury 5 HP 5MLH-LPG propane outboard motor on by its carry handle and centre it. Tighten both clamp screws firmly by hand and tie a safety line to a strong fitting. Raise and lower the bracket to check the motor clears the rudder, the pushpit and anything else through its full range of steering and tilt.

Route the propane supply line so it can’t chafe, kink or get caught in sheets or the tiller. Secure the cylinder in a vented locker or a sturdy bracket where it can’t move. Check the connection, open the valve slowly, and check for any smell of gas before starting.

Then check the oil, clip on the lanyard, put it in neutral and start. Let it idle a minute and look for the cooling telltale. Vary the throttle for the first couple of hours as it beds in.

Why sailors are switching to propane outboards

We’ve noticed more and more sailboat owners asking about propane over the last few years, and the reasons are pretty consistent.

The biggest one is reliability after sitting. A sailboat outboard might run for twenty minutes a weekend. Gasoline in a small carburetor doesn’t like that pattern at all. The Mercury 5 HP 5MLH-LPG propane outboard motor doesn’t care how long it’s been since the last run. Open the valve and it starts.

The second is having one fuel on board. Lots of sailboats already carry propane for cooking. Taking gasoline off the boat entirely means no more jerry cans in lockers, no more fuel smell in the cockpit and no more drips on the deck when you fill the motor at sea.

The third is cleanliness. Propane burns cleanly, and there’s no liquid fuel to spill into the water, which matters in marinas and sensitive anchorages.

The last is simplicity at the end of the season. Laying up a gasoline motor properly takes a bit of effort. Laying up a propane motor mostly means closing a valve and disconnecting a hose, then doing the usual oil change and flush.

Off season storage

Close the cylinder valve and disconnect the supply line. Flush the cooling system with fresh water. Change the engine oil and gear lube. Grease the swivel and clamp screws. Store the Mercury 5 HP 5MLH-LPG propane outboard motor upright or on the correct side, in a dry place. Store the cylinder separately, outdoors or in a ventilated area. Next season, reconnect, check the oil, and go.

Spares to keep aboard

A spare spark plug and spanner, a shear pin or prop hardware, a spare lanyard, a small bottle of engine oil, and a spare seal for your propane connector. Keep them together in a dry bag in a cockpit locker. It’s a small kit, but it covers nearly every minor problem you’re likely to have with the Mercury 5 HP 5MLH-LPG propane outboard motor on the water.

Is 5 hp enough for your sailboat?

It’s the question we get asked most after “which shaft length”, so here’s an honest guide.

For small day sailers and dinghies, 5 hp is more than enough. The Mercury 5 HP 5MLH-LPG propane outboard motor will move those boats briskly and give you plenty of control in reverse.

For light trailer sailers in sheltered water, 5 hp is usually a good match. You’ll motor at a sensible speed in calm conditions and still have something in hand against a moderate breeze or tide.

For heavier boats with a cabin, water tanks, anchors and a few crew, or for exposed coasts with strong tides and short steep seas, 5 hp can feel marginal. In that case look at the high thrust 5MLHA-LPG Sail Power, which swaps the standard prop for a lower pitch, higher thrust one that suits heavier displacement hulls, or step up to 6 hp or more.

A good rule of thumb is to look at what the boat’s builder recommends, and at what similar boats in your marina use. If most owners of your class run 5 or 6 hp, the Mercury 5 HP 5MLH-LPG propane outboard motor will fit right in. If they run 8 or 9.9, you probably want more power.

And if you’re not sure, send us the make, model and length of your boat. We’ll tell you straight whether this motor is the right size, or whether something else would serve you better. We’d much rather you end up with the right motor than the wrong one.

Paperwork, warranty and keeping records

When your Mercury 5 HP 5MLH-LPG propane 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.

Other options to consider

Mercury 5MH-LPG: the same propane motor with a 15 inch short shaft.

Mercury 5MLHA-LPG Sail Power: long shaft propane with a high thrust prop and charging system, made for sailboats.

Mercury 5MLHA Sail Power: the gasoline sailboat version, with built in tank and charging.

Mercury 4MLH: a long shaft gasoline motor if propane isn’t practical where you boat.

See the full range in our Mercury outboard motors category.

Mercury 5 HP 5MLH-LPG propane outboard motor for sale: price and worldwide shipping

The price of the Mercury 5 HP 5MLH-LPG propane outboard motor is shown at the top of this page. Buy it in the cart, or contact us for a delivered quote.

In the box

• Mercury 5 HP 5MLH-LPG propane outboard motor, new
• 3 blade aluminum propeller, fitted
• Propane fuel supply line
• Owner’s manual
• Mercury Marine 3 year factory warranty from the date of purchase

A propane cylinder isn’t included, since cylinder types and fittings differ from country to country. We’ll help you pick the right one.

Shipping

We ship worldwide by courier or freight, securely packed and tracked. Import duty and taxes depend on your country, and we’ll explain them before you pay if you ask.

Buying from us

Read our refund and return policy, check our customer reviews, and visit the about page.

Mercury 5 HP 5MLH-LPG propane outboard motor FAQ

What shaft length is it?

20 inches, long shaft.

Does it have reverse?

Yes, forward, neutral and reverse.

Does it charge a battery?

No. For charging, choose the 5MLHA-LPG Sail Power.

Is a propane tank included?

No, just the supply line. We’ll advise on the right cylinder for your country.

How heavy is it?

About 58 pounds.

Do you ship worldwide?

Yes. Contact us for a delivered quote.

Order your Mercury 5 HP 5MLH-LPG propane outboard motor

Long shaft, real reverse, and a fuel that never goes stale. For a sailboat or a tall transom boat that doesn’t get used every week, the Mercury 5 HP 5MLH-LPG propane outboard motor is an excellent choice. Add it to your cart, or ask us a question. You can also browse all our outboard motors for sale.