MERCURY 8 HP 8MH OUTBOARD MOTOR

Description

The Mercury 8 HP 8MH outboard motor is where Mercury’s portables move up to two cylinders. That means smoother running, more torque, less vibration through the tiller and a noticeable jump in how a small boat feels on the water. It’s a manual start, 15 inch short shaft, tiller steer four stroke, and it runs from a 3.2 gallon remote fuel tank that comes in the box. We have it for sale new, with the Mercury factory warranty, and ship it worldwide.

If you’ve got a jon boat, a skiff or a decent inflatable and the single cylinder motors feel a bit rough and short of breath, this is the step up. Here’s what you get with the Mercury 8 HP 8MH outboard motor, which boats it suits and how it compares with the 9.9.

On this page:

• Why the Mercury 8 HP 8MH outboard motor
• What 8MH means
• Boats it suits
• The multi-function tiller
• Features
• Specifications
• Maintenance
• 8 hp vs 9.9 hp
• Price and shipping
• FAQ

Why the Mercury 8 HP 8MH outboard motor

Two cylinders make a bigger difference than most people expect. A single cylinder motor fires once every two turns of the crank, so there’s a natural pulse to it that you feel in the tiller and hear in the exhaust. With two cylinders, the power strokes overlap, and the motor runs far more smoothly. The Mercury 8 HP 8MH outboard motor idles evenly, pulls cleanly through the rev range and is much more comfortable to steer for long days on the water.

It’s a 208 cc inline twin with a single overhead cam, pressurised oil lubrication and thermostat controlled cooling. That’s the same basic engine as Mercury’s popular 9.9 hp. The 8 is tuned slightly differently and swings a lower pitch prop, which makes it a very good fit for boats where an 8 hp limit applies, or where the extra top speed of the 9.9 isn’t needed.

At about 84 pounds, it’s heavier than the single cylinder motors, but still a portable one person can carry a short distance. It runs from a separate 3.2 gallon fuel tank with a quick connect line, both supplied, so range is no longer a worry.

We sell the Mercury 8 HP 8MH outboard motor mostly to jon boat and skiff owners, inflatable owners who want to plane properly, and anglers who fish waters with an 8 hp limit.

What “8MH” means

• 8 is the horsepower.
• M is manual start.
• H is tiller handle steering.
• No L means a 15 inch short shaft.

Related models: the 8MLH is the 20 inch long shaft, the 8EH adds electric start, and the 8ELH is electric start with a long shaft.

Boats the Mercury 8 HP 8MH outboard motor suits

Measure from the top of your transom to the bottom of the hull. About 15 inches means this short shaft motor fits. About 20 inches means you need the 8MLH.

• Jon boats with a low transom
• Aluminum skiffs and fishing boats around 10 to 14 feet
• Inflatables and RIBs in the 3 to 4 metre range, within their rating
• Yacht tenders that need to carry several people
• Small utility and work boats

On a light 12 foot aluminum boat with one or two people, the Mercury 8 HP 8MH outboard motor will usually get you on the plane. On a larger inflatable, it’s a big step up from a single cylinder motor, both in speed and in how easily the boat gets going with a load aboard. Check your boat’s capacity plate first.

The multi-function tiller

This is one of the best things about Mercury’s twin cylinder portables. Everything you need is on the tiller handle: forward, neutral and reverse shifting, the twist grip throttle with its tension adjuster, steering, and the stop switch. You never have to reach around the side of the motor to find a gear lever. One hand does it all, leaving the other free for a rod, a line or a net.

The auto ratchet tilt system is another nice touch. Lift the motor and it clicks into one of several tilt positions without you having to fiddle with a pin. There’s a shallow water drive setting too, for running with the prop a little higher over sand bars and weed.

On the water

Pull the choke if cold, check it’s in neutral, clip on the lanyard and pull. The start in gear protection means it will only start in neutral. Once running, the twin cylinder engine settles into a smooth, quiet idle. Shift with the tiller, twist the throttle, and the boat moves off cleanly. At trolling speed it’s quiet enough to hold a normal conversation, and the exhaust exits under the water through the prop hub. Full throttle is 5,000 to 6,000 rpm.

Mercury 8 HP 8MH outboard motor features

• Smooth two cylinder four stroke engine
• 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 and trim tab
• Multi-function tiller with forward, neutral and reverse shifting
• Adjustable steering tension control
• Twist grip throttle with tension control
• Thermostat controlled water cooling
• Auto ratchet tilt and trim system
• Shallow water drive
• Quiet through propeller hub exhaust
• 3.2 gallon fuel tank and fuel line included
• 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 8 HP 8MH outboard motor specifications

Mercury’s own FourStroke outboards page covers their full range. Mercury has updated some small motors to fuel injection in recent model years, so if EFI matters to you, ask us and we’ll confirm exactly what’s in stock.

Maintaining the Mercury 8 HP 8MH outboard motor

Fuel: fresh 87 octane, no more than 10% ethanol. Before any long break, disconnect the fuel line and run the motor until it stops so the carburetor is empty.

Oil: about 800 ml of 10W-30. Check the dipstick before each trip. Change it after 20 hours, then every 100 hours or yearly.

Gear case: change the gear lube yearly. Milky lube means water is getting in.

Cooling: check the telltale on every start, and flush after saltwater use. Keep an eye on the anodes and trim tab.

For general boating safety, the US Coast Guard boating safety site is worth a read wherever you are.

Questions people ask before buying the Mercury 8 HP 8MH outboard motor

“Is the jump from a single cylinder really worth the extra weight?”

For most people who keep the motor on the boat, yes. The smoothness alone changes how the boat feels, and the extra torque makes a loaded boat much more lively. If you carry your motor to the water every time, the extra 25 or so pounds is the real cost. Be honest with yourself about how often you’ll be lifting it.

“Will it plane my 12 foot tinny with two people?”

Often yes, depending on the boat’s weight and the load. With two average adults and some gear, the Mercury 8 HP 8MH outboard motor is right at the point where a light 12 foot aluminum boat gets up and goes. With two larger adults and a full cooler, the 9.9 gives you a better margin.

“Why is there no built in tank?”

Twin cylinder motors use more fuel than the little singles, so a separate tank makes more sense. The 3.2 gallon tank that comes with the motor gives you far more range than a built in tank ever could, and it sits on the floor of the boat, keeping weight low.

“Can I add electric start later?”

It’s much simpler to buy the electric start 8EH from the start, which also includes a charging system. The manual start 8MH is lighter, simpler and has nothing to go flat, which many owners prefer.

“Is it good as a kicker motor?”

Yes. Plenty of people use an 8 hp as a trolling kicker on a bigger fishing boat. For that job, the long shaft 8MLH is usually the right length, as bigger boats tend to have taller transoms.

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 8 HP 8MH outboard motor somewhere dry. Twenty minutes in autumn saves hours of frustration in spring.

Paperwork, warranty and keeping records

When your Mercury 8 HP 8MH 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 8 HP 8MH 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 8 HP 8MH 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.

Setting up the Mercury 8 HP 8MH outboard motor

At about 84 pounds, it’s worth having a second person help the first time you mount it, especially if the boat is already in the water. Centre the motor on the transom, tighten both clamp screws firmly by hand and tie a safety line from the motor to the boat. Use the auto ratchet tilt to set the running angle so the motor sits roughly vertical with the boat loaded as normal.

Place the 3.2 gallon tank on the floor of the boat where it can’t slide about, and connect the quick connect fuel line to the motor. Open the tank vent and squeeze the primer bulb until it’s firm. Check the engine oil. Clip on the lanyard, put the tiller shift in neutral, set the choke and pull. Once running, check the cooling telltale.

For the first couple of hours, vary the throttle and avoid long periods at full speed. Change the oil after the first 20 hours.

Real world setups for the Mercury 8 HP 8MH outboard motor

The river jon boat

A 12 to 14 foot jon boat on a river, two anglers, a day of drifting and running back upstream. The twin cylinder torque handles the current, the shallow water drive helps over gravel bars, and the tiller controls make one handed running easy while you watch the water.

The family tender

A 3.5 metre inflatable carrying a family ashore from a cruising yacht. The 8 hp gets it on the plane with a couple aboard and pushes it steadily with more. Reverse and the one handed tiller make coming alongside the yacht in a chop much easier.

The 8 hp lake

Some lakes and reservoirs around the world set horsepower limits. Where the cap is 8 hp, the Mercury 8 HP 8MH outboard motor gives you the most power you’re allowed, from a smooth twin cylinder engine.

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 8 HP 8MH 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 8 HP 8MH 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.

Mercury 8 HP 8MH outboard motor vs the 9.9 hp

The 8 and the 9.9MH share the same twin cylinder engine and the same weight. The 9.9 gives a bit more top end, the 8 costs a little less. If you boat on waters with an 8 hp limit, or your boat is rated for 8 hp maximum, the 8 is the obvious choice. If not, many buyers go for the 9.9 for the extra reserve. Neither is a wrong answer.

Compared with the single cylinder 6MH, the 8 is smoother and more powerful, but about 27 pounds heavier and uses a separate tank.

See all our twin cylinder portables in the Mercury 9.9 HP section and the main Mercury outboard motors category.

Mercury 8 HP 8MH outboard motor for sale: price and worldwide shipping

The price of the Mercury 8 HP 8MH outboard motor is at the top of this page. Add it to your cart, or contact us for a delivered quote.

In the box

• Mercury 8 HP 8MH outboard motor, new
• 3.2 gallon fuel tank and quick connect fuel line
• 3 blade aluminum propeller, fitted
• Owner’s manual
• Mercury Marine 3 year factory warranty from the date of purchase

Shipping

We ship worldwide by courier or freight, crated or boxed securely, with tracking. We’ll explain import duty and taxes for your country before you pay if you ask.

Buying from us

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

Mercury 8 HP 8MH outboard motor FAQ

Is the Mercury 8 HP 8MH outboard motor a two cylinder?

Yes, a 208 cc inline twin four stroke.

Does it come with a fuel tank?

Yes, a 3.2 gallon tank and fuel line.

How heavy is it?

About 84 pounds.

Does it charge a battery?

Not as standard. An optional 12V 76W charging kit can be fitted. The electric start 8EH includes charging.

Is it new?

Yes, with the full Mercury factory warranty.

Do you ship worldwide?

Yes. Contact us for a delivered quote.

Order your Mercury 8 HP 8MH outboard motor

Twin cylinder smoothness, a do-everything tiller and a proper fuel tank, in a motor one person can still lift. Add the Mercury 8 HP 8MH outboard motor to your cart, or ask us a question. You can also browse all our outboard motors for sale.