All the 115hp outboard engines compared

Not everyone wants or needs a big boat. If yours is a trailer boat stretching anywhere between 4.5 metres to 5.0 metres in fibreglass or aluminium, chances are you’re looking at fitting an outboard engine rated to around 115hp.

The good news is you’re still spoilt for choice at this end of the market, even if you’re now limited to the very latest in four-stroke performance technology.

Irrespective of whether you can buy a non-compliant, older-style carby outboard engine or not, why would you want to? The old engines were (past tense used deliberately) positively prehistoric. Yes, they were cheaper, but they were no longer much lighter than an equivalent clean-technology outboard engine, and they were somewhat unpleasant things to use – loud, smelly, rough and clunky.

Modern, low-emission four-stroke and direct fuel-injection two-stroke (Evinrude E-TEC and Tohatsu TLDI) outboard engines run smoother and quieter and use up to half the amount of fuel of an old carby or electronic fuel injection two-stroke. The old two-stroke engines really are dinosaurs.

Outboard engines are all very safe, reliable, durable and user-friendly. Huge advances in technology are reflected in improvements in power-to-weight ratios for these engines pretty much across the board and in the increased torque and low-down power delivery of the four-stroke outboard engines in particular.

Buyers also have ample choice of 115hp to 140hp outboard engine models. Let's now examine the individual offerings from each of the five top engine makers.

Yamaha was the first outboard engine maker to launch a 115hp four-stroke outboard engine in 1999. It’s had a long time, then, to refine the formula.

The Yamaha 115B, launched in Australia in 2014, is the second generation of the Japanese outboard engine maker’s 115hp model.

The F115B features a 1.832cc-litre four-cylinder block that at the time of its launch made it the lightest 115hp powerplant on the market. One of the big changes between generations was the shift from dual ram power tilt and trim unit to a single unit, and a larger bore to add more torque.

Features include a beefy 35-amp alternator at WOT, with 28 amps provided from just 1000rpm, making it well suited to running electronics while trolling.

Digital speed and tacho gauges and Yamaha’s CommandLink gauges that display engine functions are optional.

Specifications*
Model: Yamaha F115B FourStroke 115hp
Engine type: Four-stroke DFI
Cylinders: In-line 4-cyl, 16 valve
Fuel delivery: Direct injection
Weight: 171kg (lightest model)
Displacement: 1832cc
Bore/stroke: 81mm x 88.9mm (undersquare)
Maximum output: 115hp@5500rpm
Operating range: 5300-6300rpm
Shaft length: 508mm (20-inch), 635mm (25-inch)
Alternator: 35 amps, 28 amps @ 1000rpm
Trim method: Power trim/tilt
Gear ratio: 2.15:1
Counter rotation: Available
Servicing: Annually (or every 100 hours after first service)
Emissions rating: CARB three-star
Warranty: 4 years (recreational use)

Mercury will become the preferred supplier once the last of the Evinrude stocks in Australia are sold out.

Mercury’s 115hp four-stroke outboard engine is sold across four different models; the performance-oriented ProXS; all-rounder FourStroke; commercial-grade SeaPro; and Four Stroke Command Thrust optimised for larger boats.

You might notice that the 115hp Mercury range is slightly lighter than its Yamaha equivalent. Part of that is down to the fact that this outboard engine uses a single overhead cam rather than a twin-cam setup.

The ProXS range is optimised for running fast for long hours; if getting to and from the fishing ground as quickly and efficiently as possible, this is the choice for you.

All these four-stroke outboard engines share a common platform, a 2.1-litre four-cylinder block with just the single overhead camshaft.

The SeaPro outboard engine spins the slowest, with an operating range of 5000-5500rpm and without the option of electronic fuel injection to give it the longevity needed for commercial operations, while the Pro XS version spins from 5300-6300rpm. The more recreational boat-friendly FourStroke revs from 5000-6000rpm.

The Mercury 115 ProXS comes standard with Command Thrust, a higher gearcase ratio to help it lift heavier boats up onto the plane. Command Thrust is also optional on the FourStroke and SeaPro models.

All use hydraulic power steering, apart from dual-engine applications of the FourStroke version, which has the option of adding electro-hydraulic steering.

Specifications
Model: Mercury 115 FourStroke/ProXS/SeaPro 115hp
Engine type: Four-stroke DFI
Cylinders: In-line 4-cyl, 8 valves
Fuel delivery: Direct injection (FourStroke/Pro XS)
Weight: 163kg (Pro XS lightest model)/165kg (FourStroke, SeaPro lightest model)
Displacement: 2.1L
Bore/stroke: 90.0mm x 81.0mm (oversquare)
Maximum output: 115hp
Operating range: 5300-6300rpm
Shaft length: 508mm (20-inch), 635mm (25-inch)
Alternator: 35 amps
Trim method: Power trim/tilt
Gear ratio: 2.07:1
Counter rotation: Available
Servicing: Annually (or every 100 hours after first service)
Emissions rating: CARB three-star
Warranty: 6 years (recreational use)

If a good balance on the back of the boat is a priority, the Suzuki DF115 range could be the answer.

The latest generation of the DF115 – available in either stock 115A and visually enhanced SS form – keeps the outboard engine’s offset driveshaft that places the powerhead forward of the shaft.

This means the engine’s centre of gravity sits more forward than competitors and helps to improve handling on boats that can feel stern-heavy or are sensitive to steering inputs.

One of the other big differences with the Suzuki outboard engines is that they run a higher gear ratio than theory competitors. This allows them to swing a larger propellor and push a mich higher load than rivals.

Of note, though, the Suzuki outboard engines require a minimum diet of 91RON fuel, meaning that at the petrol station you’ll be reaching for the 95RON pump by default.

This engine also gains Suzuki’s one-touch starting – flick the key once on the ignition cycle and the outboard will crank itself into life.

Suzuki’s troll mode system, which allows the engine to idle up in 50rpm increments, is an option.

Suzuki has also recently launched its new Suzuki System Diagnostics App, which allows owners to scan a QR code displayed in the digital multifunction gauge to show engine diagnostics.

Specifications
Model: Suzuki DF115SS/DF115A 115hp
Engine type: Four-stroke DFI
Cylinders: In-line 4-cyl, 16 valves
Fuel delivery: Direct injection (FourStroke/Pro XS)
Weight: 179kg (DF115SS, lightest model)/182kg (DF115A, lightest model)
Displacement: 2044cc
Bore/stroke: 86.0mm x 88.0mm (undersquare)
Maximum output: 115hp
Operating range: 5000-6000rpm
Shaft length: 508mm (20-inch), 635mm (25-inch)
Alternator: 40 amps
Trim method: Power trim/tilt
Gear ratio: 2.59:1
Counter rotation: Available
Servicing: Annually (or every 100 hours after first service)
Emissions rating: CARB three-star
Warranty: 6 years (recreational use)

The Honda BF115, adapted from an engine used for the Honda Accord car range, is the big boy of the 115hp outboard engine sandpit.

The engine is also supplied to fellow Japanese outboard engine brand Tohatsu where it’s marketed as the BTF115A, so we’ve included it here.

This outboard engine is the heaviest among those in the 155hp power band by a significant margin. But to its credit, it gets the same road-going technology that makes the Accord a renowned fuel miser – in its marine version it is called BLAST (Boosted Low Speed Torque).

This, combined with the big 2.4-litre displacement, gives the outboard engine some serious performance cred low down in the rev range.

The engine is more suited to bigger vessels; think big, beamy fibreglass boats where hole-shot performance would suffer from a lesser outboard engine hanging off the transom.

The engine uses two counterbalancing shafts that minimise vibration to make it one of the smoothest outboard engines on the market.

Specifications
Model: Honda BF115/Tohatsu BFT115A 115hp
Engine type: Four-stroke DFI
Cylinders: In-line 4-cyl, 16 valves
Fuel delivery: Direct injection
Weight: 217kg (lightest model)
Displacement: 2354cc
Bore/stroke: 87.0mm x 99.0mm (undersquare)
Maximum output: 115hp
Operating range: 4500-6000rpm
Shaft length: 508mm (20-inch), 635mm (25-inch)
Alternator: 40 amps
Trim method: Power trim/tilt
Gear ratio: 2.14:1
Counter rotation: Available
Servicing: Annually (or every 100 hours after first service)
Emissions rating: CARB three-star
Warranty: 7 years (recreational use)