All the 15hp outboard engines compared

You’ve got a runabout, but which 15hp outboard engine will you stick on the back of it? Outboards in this category are the go-to engines for powering 3.5-metre to 3.7-metre alloy tinnies, car toppers and inflatables.

Here’s a snapshot of all the major offerings, their strengths and weaknesses, and their specs, to help you make an informed purchase.

The Honda BF15 was first launched back in 2002 alongside its twin, the BF20. Because both engines share the same architecture and weight, the larger BF20 has generally been the more popular of the two over the years.

That said, if a 15hp is the maximum you can place on the back of your boat, then the BF15 is a sound choice, as it is exceptionally smooth, reliable and easy to pull start – thanks to automatic decompression and Honda’s auto choke feature called Auto Start Enrichment.

The BF15 is a tiller-steer outboard engine, but it is available with electric starting and with gas assist or power tilt to lift the drive leg.

Displacing 350cc, the BF15 is a relatively large-capacity in-line two-cylinder single overhead cam outboard engine, so it is quite punchy and powerful.

The BF15 engine also has a ‘long stroke’ design that is claimed to provide more torque at low and mid-range revs, along with optimum fuel efficiency.

Unlike most of its more modern rivals that have battery-free electronic fuel injection systems, the Honda has an old-school single carburettor, albeit the carby working in harmony with Honda’s microprocessor-controlled PGM ignition to provide the ideal air/fuel mixture for strong performance and good fuel economy.

When launched, the Honda BF15 and BF20 twins were the lightest four-stroke outboard engines on the market, with the manual-start, short-shaft models weighing 46.5kg.

Today, with slightly lighter rival models, this weight statistic still stands up very well.

Other key features on this outboard engine include an alternator that delivers 12 amps at 3000rpm for electric models; an engine alert fault protection system; front-mount gear shift; extended twist-grip throttle; reverse exhaust relief; and a fold-away carry handle that is ideally balanced for enhanced portability.

The Honda BF15 is also available as a Power Thrust, lower gear ratio model called the BFP15.

Specifications
Model: Honda BF15
Engine type: SOHC 4-valve
Cylinders: In-line 2-cylinder
Starting system: Recoil/electric
Fuel delivery: Single carburettor
Weight: 46.5kg (lightest model)
Displacement: 350cc
Bore x stroke: 59mm x 64mm
Maximum output: 15hp at 5000rpm
Operating range: 4500rpm to 5500rpm
Shaft length: 381mm (15-inch)/508mm (20-inch)/635mm (25-inch)
Alternator: 12A (electric), 6A (manual)
Trim method: Manual/power-tilt
Gear ratio: 2.08:1
Steering control: Tiller
Servicing: Annually (or every 100 hours after first service)
Emissions rating: CARB three-star
Warranty: 7 years (5+2 recreational use)
More information: www.marine.honda.com.au

Launched in 2017-18, the 15hp Mercury two-cylinder four-stroke outboard is the latest, most modern 15hp portable engine on the market.

Designed in collaboration with, and built in Japan by Tohatsu, the 15hp Mercury is a single overhead cam in-line two-cylinder outboard engine with a displacement of 333cc and a bore and stroke of 61mm x 57mm.

Similar to several of its rivals, you can have the Mercury in manual start, manual tiller, and/or with electric start, forward steering and remote controls with power tilt.

The 15hp Mercury is also one of three outboards in this class to feature battery-free electronic fuel injection for the absolute optimum in power and economy, regardless of the climate or elevation.

The 15hp Mercury was launched a few years ago alongside its 20hp twin, becoming immensely popular due to its user-friendly features, light 45kg short-shaft weight, and its application to a range of boating/fishing activities.

This compact little outboard engine is at home pushing a lightweight 3.7-metre fishing tinnie, as it is being used as an emergency auxiliary or ‘kicker’ motor behind a much weightier boat.

There’s also a purpose-designed Prokicker model that comes with a high-thrust four-blade propeller, in addition to a SeaPro commercial model.

A key feature of the Mercury – and one that is not available with the Tohatsu version of this engine – is a centre-mounted tiller arm that caters for left- and right-handed skippers.

This multifunction tiller arm can be adjusted horizontally and vertically, and the twist-grip throttle rotation is reversible to suit driver preference.

The gear shift is also conveniently located in the centre of the tiller arm rather than on the front of the powerhead/cowling.

Other key features include a raft of alarms/alerts for most possible fault/error situations, automatic choke and decompression for cold starts, and regular functions such as shallow-water drive, freshwater flushing, and start-in-gear protection.

Specifications
Model: Mercury 15hp
Engine type: SOHC 4-valve
Cylinders: In-line 2-cylinder
Starting system: Recoil/electric
Fuel delivery: EFI
Weight: 45kg (lightest model)
Displacement: 333cc
Bore x stroke: 61mm x 57mm
Maximum output: 15hp
Operating range: 5700rpm to 6200rpm
Shaft length: 381mm (15-inch)/508mm (20-inch)/635mm (25-inch)
Alternator: 12A (electric)
Trim method: Manual/power-tilt
Gear ratio: 2.15:1
Steering control: Tiller/remote
Servicing: Annually (or every 100 hours after first service)

Launched in 2012, Suzuki stole a march on the competition by ditching the traditional carburettor and introducing the first 15hp four-stroke outboard engine with an electronic fuel injection system that did not need a battery to power it.

The Suzuki DF15A therefore became popular with anglers and boaters who used their engines in varying climates and altitudes, as the EFI system would adjust fuel/air ratios to deliver fast starts and smooth operation to suit all conditions.

Today, despite being a number of years old, the Suzuki DF15A is more than a match for its rivals, boasting other innovations such as Suzuki’s lean burn technology for frugal fuel use, and a decent-sized 14A alternator to keep a battery charged whilst running a fish finder, lights, live bait bucket or even an audio system.

The DF15A was also introduced in 2012 as the lightest 15hp four-stroke available, at just 44kg for the short-shaft model.

Tohatsu now wears the crown for the lightest 15hp outboard with its MFS15E, but it pips the Suzuki by just 1.0kg.

Similar to its rivals, the Suzuki DF15A is a single overhead cam in-line two-cylinder engine, albeit with a slightly smaller displacement of 327cc and a bore and stroke of 60.4mm by 57mm.

The DF15A is available with optional forward-steering and remote controls, and electric start and power tilt.

Base engines have tiller steering, manual start and tilt, and are available only in short shaft (15-inch) and long shaft (20-inch) drive-leg configurations.

Similar to its competition, the DF15A has alarms and alerts for engine malfunctions, including over-revving, overheating, and low oil pressure.

Other key features include a front-mounted gear shift; steering and throttle friction control; shallow water drive; freshwater flushing port; reverse locking détente; kill switch and safety lanyard.

There’s also a choice of colours: traditional black and the more costly Cool White.

Specifications
Model: Suzuki DF15A
Engine type: Four-stroke SOHC 4-valve
Cylinders: In-line 2-cylinder
Starting system: Recoil/electric
Fuel delivery: EFI
Weight: 44kg (lightest model)
Displacement: 327cc
Bore x stroke: 60.4mm x 57mm
Maximum output: 15hp @ 5300rpm
Operating range: 5000rpm to 6000rpm
Shaft length: 381mm (15-inch)/508mm (20-inch)
Alternator: 12A (electric), 6A (manual)
Trim method: Manual/power tilt
Gear ratio: 2.08:1
Steering control: Tiller/remote
Servicing: Annually (or every 100 hours after first service)
Emissions rating: CARB three-star
Warranty: 6 years (3+3 recreational use)
More information: www.suzukimarine.com.au

Tohatsu can lay claim to having the lightest outboard in the 15hp engine class with its MFS15E short-shaft, manual-start model.

This compact in-line two-cylinder 333cc engine weighs 43.0kg, pipping the Suzuki DF15A by a single kilogram and the mechanically similar Mercury 15hp by 2.0kg.

The Mercury is slightly heavier than the Tohatsu as it uses a proprietary (and heavier) centre-mounted multifunction tiller arm and different upper body panels.

The tiller arm on the Tohatsu is also a multifunction unit, complete with a tiller-mounted throttle lever, albeit one still located near the front of the engine.

Similar to Suzuki and Mercury, Tohatsu has swapped out the old-school carburettor induction system for a battery-free electronic fuel injection to supply the optimum mix of air and fuel to the engine.

Sealed, pressurised EFI systems are also better than conventional carburettors for keeping dirt and gunk out of the fuel system – particularly after periods of inactivity.

EFI portable outboards like the MFS15 will also start easier when hot or cold, and can run more smoothly and efficiently across a range of climatic conditions and altitudes.

The Tohatsu MFS15 is available in manual and electric start, with tiller and remote controls, and with manual and power tilt.

There’s a model here to suit pretty much every small boat fishing and boating application.

Other key features include an integrated fuel filter with water indicator bowl; canister-style oil filter for easy removal; stowable/fold-away carry handle; shallow water drive; a 12-amp alternator on electric models; adjustable steering friction, freshwater flushing port (no need to run the motor) and more.

The Tohatsu MFS15 is available in two colours: traditional Tohatsu Aquamarine Blue and the optional Beluga White.

Specifications

Model: Tohatsu MFS15
Engine type: SOHC 4-valve
Cylinders: In-line 2-cylinder
Starting system: Recoil/electric
Fuel delivery: EFI
Weight: 43kg (lightest model)
Displacement: 333cc
Bore x stroke: 61mm x 57mm
Maximum output: 15hp
Operating range: 5400rpm to 6100rpm
Shaft length: 381mm (15-inch)/508mm (20-inch)/ 635mm (25-inch)
Alternator: 12A (electric)
Trim method: Manual/power-tilt
Gear ratio: 2.15:1
Steering control: Tiller/remote
Servicing: Annually (or every 100 hours after first service)
Emissions rating: CARB three star
Warranty: Five years (three + two recreational use)
More information: www.tohatsu.com.au

The Yamaha is the beefiest of the 15hp outboard engines with regard to both weight and cylinder capacity.

The F15 weighs 51.0kg, but it has the largest displacement in this engine class at 362cc, making it a favourite with boat buyers seeking plenty of grunt.

Similar to other Yamaha outboard engines, the F15 is wonderfully reliable, smooth and powerful. It might be aging compared to some 15hp rivals in this class, but it certainly still holds its own.

The Yamaha has a conventional carburettor-driven fuel system, but any difference in fuel use – as compared to the EFI-equipped motors – will be negligible in this small power engine class.

Of course EFI also helps to deliver fast starts by optimising the air/fuel mixture for all conditions. Yamaha claims to achieve equally quick and efficient engine starting by using a feature it calls ‘Prime Start’, which allows the engine to be started cold by automatically controlling the warming-up phase, thereby eliminating the need for a choke.

Manual models can also be pull-started easily, thanks to the auto decompression feature.

The Yamaha F15 has plenty of other user-friendly features, including a fresh water flushing port; three-step shallow water drive system; balanced front carry handle; an electric-start option with a 10A alternator; and a front-mount gear-shift.

However, standard F15s are not available with remote controls, power tilt, or with an extra-longshaft drive leg.

Buyers looking for remote controls will need to upgrade to the new Yamaha F20, although this battery-less EFI motor is slightly heavier.

The F20 is also available with the more advanced Yamaha multi-function tiller handle.

In noting the above, for the vast majority of Australian applications the Yamaha F15 has more than enough features and benefits to make it an attractive proposition.

Specifications: Yamaha F15
Engine type: SOHC 4-valve
Cylinders: In-line 2-cylinder
Starting system: Recoil/electric
Fuel delivery: Single carburettor
Weight: 51kg (lightest model)
Displacement: 362cc
Bore x stroke: 63mm x 58.1mm
Maximum output: 15hp
Operating range: 5000rpm to 6000rpm
Shaft length: 381mm (15-inch)/508mm (20-inch)
Alternator: 10A (electric)
Trim method: Manual
Gear ratio: 2.08:1
Steering control: Tiller
Servicing: Annually (or every 100 hours after first service)
Emissions rating: CARB three-star
Warranty: Four years (two + two recreational use)
More information: www.yamaha-motor.com.au