Inside Word on outboards

All the engines listed comply with US EPA 2006 exhaust emission regulations, but only the four strokes and the E-TEC and OptiMax 150s meet California Air Resources Board (CARB) 2008 requirements. Yamaha's HPDI 150 only meets US EPA 2006. Apart from the HPDI 150, all engines in this guide have three years of warranty coverage.

Recommended servicing requirements for the four strokes is every 50 hours (100 for the BF150) with water pump impeller replacement every 100 hours. Apart from the Yamaha F150A, which requires an initial checkup at 10 hours, the first service is at 20 hours. All the four strokes have canister-type oil filters.

The HPDI 150 requires an initial checkup at 10 hours and the OptiMax 150 at 20, followed by every 100 hours. The E-TEC 150 doesn't require powerhead servicing for the first 300 hours.

FOUR STROKES

HONDA BF150
Based on the Euro Accord automotive engine, the BF150 is up-rated from its 135hp counterpart and has variable valve timing or VTEC, the same as the BF225. This ensures the intake valves are opened at the right time according to engine revs to maximise power in the upper rev range or around 4500rpm.

The BF150 also has a Variable Air Intake System which lengthens the air intake flow at low speeds to increase bottom end torque, but shortens the flow at high revs (above about 4000) to improve engine 'breathing' and increase power.

Like the BF135, the 150 has counter-rotating balance shafts needed in four-cylinder engines over 2.2lt and chain drive for the camshafts to eliminate the possibility of the valves contacting the piston crowns, as can happen in an 'interference' engine should the timing belt break. The hydraulically-tensioned chain is designed to last the life of the engine and runs in an oil bath and the only belt drive is for the alternator.

So far, this engine has not been tested but owner reports indicate it provides significantly better performance than its BF135 counterpart and would suit hulls to six metres.

The saltwater corrosion resistance should be comparable with the proven BF130.

JOHNSON/SUZUKI DF150
The less powerful of Suzuki's largest-displacement four-cylinder engines, the DF150 was released locally last year and, although designed as a marine engine, automotive industry sources say it was intended for use in a US-built GM SUV.

Like Honda's BF150, the DF150 has chain drive for the camshafts and twin counter-rotating balance shafts, sensible in an 'interference' engine. The DF150 also has Multi-Stage Induction (MSI), where the length of the air intake manifold pipes is changed according to engine revs. This provides the optimum volume of fresh air into the chambers to improve combustion and boost bottom-end torque.

As the revs pass a pre-set limit, butterfly valves in the direct intake pipes open and air reaches the combustion chambers in a far shorter time, increasing 'breathing' ability. However, the DF150 misses out on the continuously variable valve timing of its DF175 counterpart.

The DF150 has an offset driveshaft, placing engine weight further forward for less stress on the transom and enabling an initial reduction to be incorporated here. Combined with the final reduction in the gear case, this increases the overall reduction without increasing gear case torpedo diameter.

On a 6.25m Signature 600C, spinning a 21-inch pitch stainless steel Suzuki prop and pushing 1500kg, the demo DF150 was perfectly matched to this hull. It started instantly hot or cold and didn't blow any oil smoke.

Trolling at 600rpm, we averaged 4.4km/h using 2.1lt/h and planed cleanly at 22km/h on 3000rpm. Cruising at 4000rpm, we averaged 40.5km/h using 25.3lt/h and the Wide Open Throttle average was 58.5km/h at 5500rpm using 63.5lt/h.

Servicing the DF150 appears straightforward with the ignition coils being incorporated with the spark plugs and all wiring neatly routed. Based on my long-term testing of other Suzuki outboards in the past four years, the DF150 should have very good saltwater corrosion resistance.

MARINER/MERCURY VERADO 150
The middle of the range of a trio of supercharged and intercooled four-cylinder four strokes, the Verado 135 should provide stunning performance on a hull capable of handling its relatively hefty weight.

A four-cylinder version of the Verado 200 to 275 straight six range, the 150 has a comprehensive range of standard features including SmartCraft Digital Throttle and Shift (DTS) and SmartCraft Engine Guardian, which progressively reduces revs or shuts down the engine should it overheat or experience low oil pressure.

Hydraulic or electro-hydraulic power steering systems are available, although based on my testing of the Verado 250, the latter would be my choice.

YAMAHA F150A
Released locally three years ago, the F150A was designed as a marine engine with the intention of slotting it into a US-built Ford SUV. It has the second-largest piston displacement of all the 150s and, unusual for a four-stroke, outperforms the OptiMax 150.

Although the F150A has the same cylinder bore diameter as its V6 F225A counterpart the piston stroke is much longer. Twin counter-rotating balance shafts improve the inherent lack of engine balance in big four-cylinder engines (over 2.2lt) and, surprisingly, give the demo F150A lower vibration levels than those of the OptiMax 150. Unfortunately, though, the balance shafts and camshafts are driven by a toothed rubber belt.

On a 6.63m Haines Hunter Patriot 650, spinning a 19-inch Yamaha stainless steel prop and pushing 1900kg, the demo F150A outperformed the OptiMax 150 on a six-metre Seafarer Victory spinning a 17-inch Quicksilver Vengeance prop and pushing 1800kg.

The F150A started instantly hot or cold and didn't blow any oil smoke. It trolled us at 4.8km/h on 600rpm using 2lt/h and planed us cleanly at 22.5km/h on 2800 revs. Cruising at 4000rpm, the averages were 44.5km/h and 24.6lt/h and, from 4000rpm, with the throttle lever floored, acceleration was the same as the OptiMax out to WOT.

The WOT averages were 71km/h and 5750rpm using 61.7lt/h and was much quieter with none of the V6 Mercury 'howl'.
Powerhead access is very good, with the engine oil level dipstick easily reached. The vertically-mounted canister-type oil filter reduces oil spillage when changing the oil.

The F150A already has a proven reputation for saltwater corrosion resistance.

TWO-STROKES

EVINRUDE E-TEC 150
De-rated from its 175 and 200 counterparts, the 150 is the smallest-displacement V6 E-TEC model available. But despite its massive torque output, 310Nm at only 3500rpm, which is higher than comparable four strokes in this power range, it's significantly lighter than any of them.

This relatively lighter weight makes it a viable choice for performance fishing hulls down to five metres.
A clever feature with the 150 is the variable-voltage alternator, which powers the engine management computer, eliminating the need for an external battery, apart from the one to start the engine. The 150 is also available with I-Command - a digital fuel flow display similar to Mercury's SmartCraft.

The 150 uses Bombardier's single-stage fuel injection, whereby via solenoid-controlled unit injectors only petrol is injected into the combustion chambers between 36 and 50 bar or 500 to 700 psi. A mix of stratified and homogenous combustion is used and below 1800rpm the fuel is injected several times during each single spray duration to create a 'pocket' of rich air/fuel mix near the spark plugs. But the overall air/fuel ratio is only 40:1, 2.8 times leaner than the air/fuel ratio used in a four-stroke engine.

Above 1800rpm, homogenous combustion is used with an air/fuel ratio of around 25:1 throughout the combustion chambers. But because the fuel droplet size is up to 30 microns, the E-TEC system doesn't deliver the overall fuel efficiency of the Orbital Combustion Process used in OptiMax engines.

Mounted on a side console Haines Hunter Prostrike 490, spinning an 18-inch pitch stainless steel Raker prop and pushing 1100kg, the demo E-TEC started instantly hot or cold and didn't blow any oil smoke although there was a slight oil smell when backing upwind. It trolled us at a vibration-free 3.7km/h on 500rpm using 1.3lt/h. It planed us cleanly at 32.2km/h on 2400rpm. On just 3000rpm we averaged 49.9km/h using 20.6lt/h and, at 4000rpm, we averaged 72.5km/h using 35.7lt/h.

When the throttle lever was opened rapidly, we were thrown back in our seats out to WOT where the averages were 93.5km/h and 63.4lt/h at 5200 revs.

Powerhead access is very good and the spark plugs and unit injectors are easily reached, while a flywheel fan reduces operating temperatures of the alternator and powerhead wiring. Although Bombardier Recreational Products says servicing is not required for 300 hours or three years, most dealers I've spoken with recommend changing the gear oil and greasing the throttle/gearshift linkages every 100 hours or once a year.

MARINER/MERCURY OPTIMAX 150
The middle of a trio of Mercury Marine's smaller-displacement V6 DFI engines, the 150 has proven very reliable since its local release in 1998.

The 150 uses the Orbital Combustion Process, which mixes fuel at 80 psi or 5.7 bar with air at 90 psi or 6.4 bar and injects this atomised air/fuel mix into the combustion chambers at only five microns. Combined with the 'stratified' air/fuel ratios of about 40:1, this results in lower fuel consumption when trolling than any of the direct competition. When the OCP switches to 'homogenous' the air/fuel ratio is about 25:1.

The Motorola microprocessor automatically alters the air/fuel ratios according to the engine load and barometric pressure and, when the engine is brand new or has been reconditioned, the management system can be programmed to automatically double the fuel/oil ratios for the first five hours. Combined with the digital ignition system and electric oil pump the OptiMax now complies with CARB 2008 whereas earlier models didn't.

Like all Optimax models the 150 is SmartCraft-compatible, allowing it to operate digital fuel-flow meters, range-to-empty and other goodies associated with this brilliant system.

On a six-metre Seafarer Victory, spinning a 17-inch Quicksilver Vengeance stainless steel prop and pushing 1800kg, the demo 150 started instantly hot or cold and didn't blow any oil smoke, although there was a slight oil smell when backing upwind. It trolled us at 4.7km/h at 650rpm using 1.1lt/h.

It achieved a clean plane at 29.7km/h and 3200rpm and cruised quietly at 48.1km/h and 4000rpm using 25.7lt/h. The WOT averages were 65.8km/h and 57.9lt/h at 5050rpm.

Servicing the 150 is straightforward and, as with water pump impeller replacement, the 1:1 drive belt for the air compressor should also be checked at 100 hours.

The OptiMax 150 has a proven reputation for saltwater survival.

YAMAHA HPDI 150
The least powerful of a trio of DFI engines, the Z150P uses a Mitsubishi-developed single-stage injection system using three pumps to raise the final injection pressure to a whopping 1000 psi or 71.4 bar.

But because the High Pressure Direct Injection system is only homogenous with an overall air/fuel ratio of 25:1, the Z150P is nowhere near as fuel efficient as its E-TEC and OptiMax competition and uses around 3lt/h when trolling. This limits its appeal to freshwater anglers.

The first pump is driven by alternating crankcase pressure, the second by an electric motor and the third via a belt-driven pump. Should the belt fail, the system can still function on the crankcase and electric pumps, giving a true 'limp home' mode, whereas with OptiMax engines if the air compressor belt breaks the DFI system simply fails to operate. The HPDI system uses an oxygen sensor in the exhaust to allow the electronic engine management system to alter the air/fuel ratios and spray timing according to barometric pressure.

At low revs, there's none of the air compressor 'click' of OptiMax engines, although at higher revs a slight whine from the high pressure fuel pump is apparent.

On a Southwind SF550WR, spinning a 17-inch pitch stainless steel prop and pushing 1500kg, the demo Z150P started instantly hot or cold and, interestingly, there was no oil smell at any time despite not having a stratified idle circuit. There was insufficient time to conduct trolling tests but we planed cleanly at 28.9km/h and 2900rpm. We cruised quietly at 59km/h and 4000rpm, consuming 25.6lt/h.

The WOT averages were 78.7km/h and 5600rpm using 56.6lt/h. At this speed, a normal conversation could still be held at the helm.

Servicing the Z150P appears straightforward and a nice touch is that standard Yamalube oil can be used to reduce oil costs. The Z150P also has a proven reputation for saltwater corrosion resistance.

AND THE WINNERS ARE...

In this power range it's very hard to pick a clear winner.

The Johnson/Suzuki DF150 has comparable holeshot acceleration to the OptiMax 150 and is slightly better than the Yamaha F150A, but uses more fuel than the Yammie. As with the Yammie, the DF150 is much quieter than the OptiMax 150 at WOT but on par with the E-TEC 150.

The main efficiency zone of these larger four strokes is between 2000 and 4000rpm, with the E-TEC and OptiMax engines scoring at trolling revs and at WOT.

So my recommendation for freshwater angling where the main operation is extended trolling with WOT running from and to the launching ramp is the OptiMax 150, followed by the E-TEC 150, which isn't as fuel efficient. But for offshore angling where the revs are mainly midrange, then I recommend the Johnson or Suzuki DF150 followed by Yamaha's F150A.