Mercury 5 hp Sailpower Specs
| Engine Model: Mercury Sailpower 5 hp |
| Engine Type: 4-stroke single-cylinder gasoline outboard engine |
| Total Displacement: 7.5 cu.in (123 cc) |
| Rated Engine Power: 5 Hp (3.7 kW) at 5500 rpm |
| Fuel System: Carburetor |
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The Mercury Sailpower 5 is a purpose-built
four-stroke outboard designed as the ideal auxiliary engine for
sailboats and other displacement craft. Its defining characteristics are
a direct response to the specific needs of sailors: a high-thrust
propeller for efficient low-speed maneuvering, an integrated 4-amp
alternator to maintain house battery charge, and an enhanced exhaust
system that routes gases through the propeller hub for exceptionally
quiet operation.
The engine is praised for its light weight, with the lightest model
available at just 59 lbs, making it manageable for mounting on a
sailboat transom or stowing in a lazarette. The forward-mounted gear
shift selector is a user-friendly detail that simplifies operation when
the engine is mounted in a sailboat's well. While its power output is
modest at 5 Hp, its torque-focused design provides ample control and
drive for vessels up to a significant size in various conditions,
including against wind and tide.
With features like a six-position manual trim, shallow water drive, and
low-oil and over-rev protection, the Sailpower 5 delivers the
reliability, ease of use, and durability that sailors expect from a
modern Mercury outboard.
Power: 5 HP (3.7 kW) at the propshaft.
Engine Type: Single-cylinder, 4-Stroke.
Displacement: 7.5 cubic inches (123 cc).
Bore and Stroke: 2.32 inches (59 mm) bore by 1.77 inches (45 mm) stroke.
Full Throttle RPM Range: 4500-5500 RPM.
Fuel Induction System: Carbureted.
Air Induction: Naturally Aspirated, 2-valve pushrod (overhead valve)
design.
Ignition System: Capacitive Discharge Ignition (CDI) with electronic
spark advance.
Cooling System: Water-cooled, with thermostat.
Exhaust System: Through-propeller hub, designed for quiet operation and
enhanced reverse thrust.
Starting System: Manual.
Steering and Control: Tiller handle.
Alternator Output: 4-amp (50-watt) lighting and charging coil,
specifically for maintaining a 12-volt battery.
Engine Protection Operator Warning System: Audible and/or visual alerts
for low oil pressure and engine over-rev condition.
Trim System: Manual, with 6-position adjustment.
Shallow Water Drive: Yes, with a trim range of 16 deg.
Recommended Fuel: Unleaded regular 87 octane minimum, with up to 10
percent ethanol.
Gear Shift: Forward-Neutral-Reverse.
Gearcase Ratio: 2.15:1.
Gearcase: Standard, designed for high-thrust applications.
CARB Star Rating: 3-star.
Fuel Tank Capacity (Internal): 1.1 liters (0.3 gallons).
Fuel Tank Capacity (Optional Remote): 12 liters (3.2 gallons).
The foundation of the Sailpower 5 is a compact, lightweight
single-cylinder block. This simple and robust design is a hallmark of
small four-stroke engines, prioritizing reliability and ease of
maintenance.
The cylinder head incorporates a two-valve pushrod (overhead valve)
configuration, a durable and proven design that provides excellent
low-end torque essential for pushing a displacement hull. The engine is
constructed using advanced alloys and treated with multi-layer corrosion
protection coatings to withstand the demanding marine environment,
whether in saltwater or freshwater.
The fuel system is a conventional and dependable carbureted design,
chosen for its simplicity in this small engine class. Fuel is drawn from
either the built-in 1.1-liter (0.3-gallon) internal tank or an optional
external 12-liter (3.2-gallon) tank, providing flexibility for longer
passages.
The system is designed to operate on readily available 87-octane fuel.
Maintenance is simplified with an easy-out fuel filter for periodic
cleaning or replacement.
The Mercury 5 hp Sailpower uses a wet-sump lubrication system, standard
for four-stroke engines. Engine oil is contained within the crankcase
(sump) with a total capacity of 0.45 liters. An oil pump circulates the
Mercury FourStroke Oil 10W-30 throughout the engine to lubricate the
crankshaft, connecting rod, camshaft, and valve train.
The system includes a low-oil-pressure warning sensor that alerts the
operator to potentially dangerous conditions, protecting the engine from
damage. Mercury has engineered features like a no-spill oil drain system
to make oil changes cleaner and more convenient.
The cooling system is a water-cooled design with a thermostat. A water
pump, driven by the driveshaft, draws water from outside the boat and
circulates it through passages in the cylinder block and head to
dissipate combustion heat.
The thermostat ensures the engine reaches and maintains optimal
operating temperature quickly, which improves efficiency and reduces
wear. An integrated freshwater flushing system simplifies the essential
post-operation maintenance, especially after use in salt or polluted
water.
| Mid Section and Lower Unit |
The mid section houses the driveshaft and connects the powerhead to the
lower unit, while also providing the mount for the tiller handle and
trim adjustments. The lower unit is a standard gearcase specifically
calibrated for the Sailpower model.
It contains the forward-neutral-reverse gearing with a 2.15:1 gear
ratio, which is lower (numerically higher) than a standard 5hp engine,
allowing the high-thrust propeller to spin more slowly and with greater
force. This is crucial for moving a heavy, displacement sailboat.
Shaft Length: 20 inches (508 mm) standard; a 25-inch (635 mm) version is
also available for boats with taller transoms.
Gear Ratio: 2.15:1
Gear Shift: Forward-Neutral-Reverse
The engine features a manual trim and tilt system with six adjustable
positions. This allows the operator to set the correct operating angle
of the engine for optimal thrust and boat performance.
The system also incorporates a shallow water drive feature, with a trim
range of 16 deg, allowing the engine to be tilted up partially to
navigate through very shallow water without lifting the propeller
completely out.
The Mercury Sailpower 5 is equipped with a specialized high-thrust
propeller, a key feature differentiating it from standard models. The
propeller has a diameter of 8 inches and a coarse pitch of 6 inches,
designed to generate maximum thrust at the lower speeds characteristic
of sailboat auxiliary power.
The 6-inch pitch is significantly flatter than a propeller on a
comparable engine meant for a planning dinghy, which would have a higher
pitch for greater top speed.
This "saildrive" propeller ensures the engine can efficiently move a
heavy, displacement hull and provides excellent reverse thrust for
maneuvering in tight quarters, aided by the enhanced exhaust system that
directs gases through the hub to improve grip in reverse.
Dry Weight (Lightest 20" model): 59 lbs (27 kg)
Dry Weight (Lightest 25" model): 63 lbs (28.6 kg)
Shaft Length: 20 inches (508 mm) or 25 inches (635 mm)
Engine Oil: Mercury FourStroke Oil 10W-30 is recommended.
Engine Oil Capacity: 0.45 liters.
Gearcase Lubricant: Quicksilver Premium Gear Lube is recommended.
Gearcase Lubricant Capacity: 0.195 liters.
Maintenance Features: The engine includes a no-spill oil change system,
an easy-out fuel filter, and a valve train designed to be
maintenance-free for life.
Cooling System Flushing: An easy-to-use freshwater flushing system is
integrated into the engine design for use after operation in salt or
polluted water.
Scheduled Service: Regular oil changes, gearcase lubricant changes, and
water pump impeller inspections are required per the owner's manual
schedule.
The Mercury Sailpower 5 is designed for a primary and highly specific
application: as an auxiliary outboard motor for sailboats. Its
high-thrust propeller, battery charging capability, and quiet operation
are all tailored to this role. Experienced sailors have successfully
used it on vessels ranging from 18-foot trailer sailers to 24-foot
yachts, finding it has ample power for handling tides and winds.
Beyond sailboats, its robust torque and easy operation also make it an
excellent choice for other displacement or heavy craft, including
aluminum tiller boats, jon boats, utility boats, and inflatable
soft-hull boats. The combination of a 4-amp alternator, high-thrust
propeller, and manual trim positions makes it an extremely versatile and
reliable power source for a wide range of small-boat applications.
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