115hp four-strokes and direct fuel-injection two-strokes

Name: 115hp four-strokes and direct fuel-injection two-strokes
Brand: JOHNSON

Continuing our series of guides to choosing the right low-pollution outboard for your boat, Andrew Norton compares high-end 115hp four-strokes and direct fuel-injection two-strokes

FOUR-STROKES

HONDA BF115
De-rated from its 130hp counterpart, the BF115 is based on the Accord car engine and has twin counter-rotating balance shafts and sequential multipoint EFI for smooth running across its entire rev range.

The electronic management system reduces revs to a safe level should the engine over-rev, overheat or lose oil pressure and enables the engine to idle in or out of gear at only 650rpm.

Mounted on a 5.5m fibreglass Savage Mako SP Cuddy Cabin 11, spinning a 17in stainless-steel Solas prop and pushing a total of 1200kg including two adults, the demo engine was slightly overpropped but because of its understressed powerhead still coped well with this load. Although there was insufficient time to conduct trolling speeds or fuel consumption, cruising quietly on 4000rpm the averages were 48.2kmh using 15.1lt/h, while at Wide Open Throttle we averaged 64.4kmh on 5200rpm using 36lt/h. Through full lock figure of eight turns at 4000rpm no prop ventilation occurred.

Because of its SOHC valve actuation, powerhead access is very good and the engine oil dipstick and oil filter are easily reached. Although the toothed camshaft timing belt should last around 800 hours before needing replacing I would check it for damage every 100 hours or once a year.

Providing it is freshwater-flushed after every use, the BF115 stands up well to frequent saltwater usage.

JOHNSON/SUZUKI DF115
Based on the Suzuki Vitara 4WD engine, the sequential multipoint EFI DF115 is the only four-stroke outboard in this power range to have chain-driven camshafts and two-stage reduction gearing which enables thrust-efficient coarse-pitch props to be swung without increasing gearcase torpedo diameter and consequently drag. Running in an oil bath, the camshaft chain is designed to last the life of the engine.

Its large displacement relative to the direct four-stroke Mercury and Yamaha competition gives it plenty of torque and for holeshot acceleration it's unmatched by these or the overweight BF115. Yet despite not having balance shafts it's almost as smooth as the BF115.

Mounted on a Clark 5.7 Centre Console the demo DF115 returned stunning performance, even by DFI two-stroke standards. Spinning a 17in pitch stainless-steel prop and pushing a total of 1100kg including four adults, the DF115 trolled at 6.9kmh on 700rpm using 1.2lt/h. Cruising quietly at 4000rpm the DF115 returned an average of 40.0kmh using 16.5lt/h and through tight figure of eight turns at 4000rpm there was no prop ventilation.

At WOT the DF115 averaged 57.9kmh on 5750rpm using 39.0lt/h and was significantly quieter than its direct DFI competition.

Access to the powerhead is good with the oil dipstick easily reached and the oil sump has sufficient capacity to effectively reduce oil sludging between oil/filter changes. The DF115 has good saltwater corrosion resistance.

MERCURY MARINER F115
Although it utilises the same basic powerhead as Yamaha's F115A, the multipoint sequential EFI F115 differs in cylinder head and manifold, leg and lower unit design and engine management componentry. Unfortunately Mercury's approach to over-engineering its four-strokes does make the EFI F115 incur a two per cent weight penalty over the F115A, but then the Merc develops two per cent more propshaft horsepower at the same revs. However until the F115A counter rotation is not available.

While the F115 does have engine protection features that automatically reduce revs should the engine overheat or suffer low oil pressure, the electronic control unit is first generation and misses out on the brilliant Motorola PCM 555 microprocessor. This prevents interfacing with the SmartCraft system available with Mercury's 30–60hp EFI four-strokes, which allows for connection of a digital fuel flowmeter.

Mounted on a 5.5m Seafarer Ventura and spinning a 16in stainless-steel Quicksilver Vengeance prop, the demo EFI F115 provided excellent performance. Pushing a total of 1380kg including two adults, the F115 trolled us at 4.1kmh on 750rpm using 1.3lt/h and cruised quietly at 42.2kmh on 4000rpm consuming 15.5lt/h with no prop ventilation occurring through full lock figure of eight turns at these revs. The WOT average was 69.2kmh on 6000rpm consuming 38.5lt/h.

Servicing the Merc appears straightforward but being an inference engine I would check the camshaft belt for damage every 100 hours or once a year. The F115 has proven saltwater corrosion resistance.

YAMAHA F115A
The first of Yamaha's multipoint sequential EFI four-stroke outboards, the F115A is a "stroked" version of the F100A engine based on the Ford Fiesta car. Although it has belt driven camshafts, valve clearance adjustment is not required for the first 400 hours and the engine has automatic rev reduction should over-revving, overheating or low oil pressure occur. Because it trolls at a low 600rpm it's ideal for freshwater anglers.

Mounted on a 5.5m Southwind/Southern Star SR550BR bowrider, spinning a 19in Yamaha stainless-steel prop and pushing a total of 1150kg including three adults, the demo F115A trolled at 4.0kmh using 1.2lt/h. It cruised effortlessly at 33.9kmh on 4000rpm using 15.7lt/h according to the digital Yamaha flowmeter fitted and through full lock figure of eight turns at these revs no prop ventilation occurred. The WOT average was 69.9kmh on 5500rpm using 37.5lt/h.

On a Quintrex 560 Freedom Sport Millennium-hulled bowrider, spinning the same prop and pushing the same weight (this time with four adults aboard) the demo F115A averaged 39.0kmh on 4000rpm and 64.9kmh on 6000rpm. On this hull holeshot acceleration was excellent for a four-stroke 115.

Again, servicing the F115A is straightforward, but as it is an interference engine, check the camshaft belt for damage every 100 hours or once a year. The F115A has proven saltwater corrosion resistance.

TWO-STROKES
EVINRUDE E-TEC 115
A development of the Ficht 115 and later 115 DI, the E-Tec 115 is essentially the same engine but has the much higher fuel injection pressure of 36 to 50bar (500–700psi) of its 90hp counterpart. Also the dedicated battery charging output is now 50amp.

E-Tec uses a mix of stratified and homogenous combustion with air/fuel ratios varying from 40:1 to 25:1 and as with the 90, an external battery is not required for the electronic engine management system to function. The 115 has automatic rev reduction or even total engine shutdown should over-revving, overheating or low oil pressure occur. A sensible feature is the deeper gear ratio in extra longshaft models with BRP logically reasoning these models will be used on heavier hulls.

Mounted on a Quintrex 530 Freedom Sport Millennium-hull bowrider, spinning a 17in stainless-steel prop and pushing a total of 1010kg including three adults, the demo longshaft 115 DI trolled at 4.4kmh on 650rpm using 1.0lt/h. Cruising quietly at 4000rpm the averages were 44.7kmh using 21lt/h and through full lock figure of eight turns at these revs no prop ventilation occurred. At WOT the 115 DI averaged 64.9kmh on 5550rpm and used 45lt/h with slightly higher noise levels than the direct four-stroke competition.

As the E-Tec 115 was not yet released at the time of writing, it could not be tested. Based on my testing of the E-Tec 90, I think the E-Tec 115 should provide similar fuel efficiency to its 115 DI predecessor.

Because there's no belt-driven air compressor or alternator, powerhead access is very good and components such as the fuel injectors and spark plugs are easily reached. And because it's based on the long-running carburetted Johnson 115 the saltwater corrosion resistance is excellent.

MERCURY MARINER OPTIMAX 115
The OptiMax is the first direct-injection 115 to meet California Air Resources Board (CARB) 2008 exhaust emission regulations, whereas the Evinrude 115 DI currently meets only CARB 2004. The OptiMax 115 can also be fitted with TrollControl to reduce engine revs to only 400 for slow-speed trolling and is SmartCraft-compatible, giving fuel flow and range to empty info.

The OptiMax 115 uses the Orbital Combustion Process which mixes fuel pressurised to 5.7bar (80psi) with air at 6.4bar (90psi) which is then injected directly into the combustion chambers. A mix of stratified and homogenous combustion is used with the air/fuel ratios varying from 40:1 to 25:1.

The 115 has incredible overall fuel efficiency for its output. The demo engine was spinning an 18in pitch stainless-steel Quicksilver Vengeance prop and was mounted on a Stacer 565 Coral Master Sports runabout, which displaced a total of one tonne including the two adults aboard. It trolled us at 4.7kmh on 650rpm using a mere 0.7lt/h according to the SmartCraft system fitted and maintained an economical cruise of 27.6kmh on 3000rpm using only 9.6lt/h. At 4000rpm the averages were 44.4kmh and 17.6lt/h and no prop ventilation occurred through full lock figure of eight turns at these revs.

The WOT average was 64.9kmh on 5500rpm using 37.6lt/h but noise levels were higher than any of the direct competition including the Evinrude.

Servicing the OptiMax appears straightforward with the fuel injectors, belt-driven air compressor and alternator easily reached. The air compressor belt should be checked for damage every 100 hours or once a year. Although it's too new to judge saltwater corrosion resistance, based on Mercury Marine's efforts in building its engines the 115 should survive frequent saltwater usage very well.

BACK-UP AND WARRANTY
All the engines listed comply with US EPA 2006 exhaust emission regulations but in addition the Honda BF115, Johnson/Suzuki DF115, Evinrude E-Tec 115 and Mercury Mariner OptiMax 115 meet California Air Resources Board (CARB) 2008 requirements. The DF115 also meets EU2005 and the E-Tec 115 EU2006 requirements, both of which take into account noise emissions. The Yamaha F115A has a two-year warranty while the Honda BF115, Suzuki DF115, Mercury Mariner F115, Evinrude E-Tec 115 and OptiMax 115 get three years of coverage.

Recommended servicing requirements for the four-strokes are every 50 hours (100 for the BF115) with water pump impeller replacement every 100 hours. Apart from the Yamaha F115A, the first service is at 20 hours when the valve clearances should be checked. All the four-strokes have canister-type oil filters. The OptiMax 115 requires servicing every 100 hours and the E-Tec 115 every 300.

The Tohatsu Corporation has a direct-injection TLDI 115 undergoing trials in Japan but the Australian distributor, Lakeside Marine, has been unable to provide a timeframe for the engine's Aussie release.

All outboards in this 115hp guide are arranged alphabetically.

AND THE WINNER IS...
Having tested all but the E-Tec 115 for fuel efficiency, slow trolling ability, holeshot acceleration, relatively low maintenance costs and SmartCraft compatibility, my choice is the OptiMax 115!

115hp Four-Strokes
Engine	Honda 115	Johnson/Suzuki 115	Mercury Mariner 115	Yamaha 115
Engine type	Crossflow four-cylinder
Valves	16	16	16	16
Valve actuations	SOHC	DOHC	DOHC	DOHC
Drive	Belt	Chain	Belt	Belt
Prop HP @ rpm	113.4/5500	113.4/5500	115.3/5500	113.4/5500
WOT rev range	5000–6000	5000–6000	5000–6000	5000–6000
Piston displ. (cc)	2254	1950	1741	1741
Bore x stroke (mm)	86x97	84x88	79x88.8	79x88.8
Ignition system	All Electronic engine management
Charging circuit (amps)	40 with voltage regulation 25 with voltage regulation
Break-in period (hrs)	10	10	10	10
Fuel delivery	Multipoint sequential EFI
Fuel type	ULP 91 RON	ULP 91 RON	ULP 91 RON	ULP 91 RON
Fuel capacity (lt)	Portable tank not supplied
Oil type (SAE)	10W30	10W40	10W30	10W40
Oil capacity (lt)	5.6	5.5	4.5	4.5
Gear ratios	2:1	2.59:1	2.07:1	2.15:1
Standard Transom heights (in)	20/25	20/25	20/25	20/25
Weights (kg) Longshaft	229	189	194	185
Weights (kg) Extra-long	234	194	199	189.5
Rec. retail Longshaft	$16,020	$14,507	TBA	$16,759
Rec. retail Extralong	$16,329	$14,639	TBA	$17,298
* Weights electric start remote control versions with power trim. Prices accurate at press time

115hp Two-Strokes
Engine	Evinrude 115	OptiMax 115
Engine type	DFI two-stroke
Prop HP @ rpm	115.3/5500	115.0/5375
WOT rev range	5250-5750	5000–5750
Piston displ. (cc)	1726	1524
Bore x stroke (mm)	91x66	92x76
Ignition system	All electronic engine management
Charging circuit (amps)	50 underflywheel	60 belt-driven
Break-in period (hrs)	5	5
Fuel/air scavenging	Loopcharged	Loopcharged
Fuel delivery	High pressure single stage	Low pressure dual stage
Fuel type	ULP 91 RON	ULP 91 RON
Fuel capacity	Portable tank not supplied
Oil capacity (lt)	11.4 in boat	4.7 undercowl
Gear ratios	2:1/2.25:1	2.07:1
Transom heights (in)	20/25	20/25
Weights (kg) Longshaft	173	170
Weights (kg) Extra-long	177	175
Rec. retail Longshaft	Six models available	$17,106
Rec. retail Extralong	Avg RRP $10,200	$17,469
* Weights are for remote control versions with power trim and tilt. Prices correct at press time.

115hp four-strokes and direct fuel-injection two-strokes

Tags