OMC Evinrude's new Suzuki-designed four-strokes

Released on the Aussie market about a year ago, the Evinrude 70 is the result of a joint effort between Suzuki and OMC, and is the teaming's first big four-stroke outboard.

Since its release, this beautifully-smooth and quiet motor which utilises the long-running 1300cc Sierra four-wheel drive powerhead has set new standards for mid-range four-strokes. Standard features include an engine management system, with multipoint fuel-injection and a deep-ratio gearcase for efficient conversion of engine torque to thrust at the prop.

Having now tested three fuel-injected four-strokes, namely the Evinrude 50 and 70, and Honda BF115/130, I believe EFI is the way to go for motors that would normally utilise three or more carbies. Apart from its diagnostic facility that greatly reduces tune-up time, EFI also maintains the correct air/fuel ratio according to barometric pressure and adjusts for other operating variables such as cold starting. And if you fish high altitude dams, the motor never runs rich as do carbie engines.

Of course, with a carbie motor, smaller jets can be installed if using the motor for extended periods at high altitude. But if the motor is then used at sea level without re-installing the original jets, it will run too lean an air/fuel mix, resulting in overheating and eventually burned exhaust valves.

Although the Evinrude 70 is designed to compete against 70 hp two-strokes and the Honda BF75, it develops similar torque to the two-stroke Yamaha 90 a fact borne out when I tested the motor recently against its Johnson 70 counterpart (which has the same gear ratio) on the same hull.

Mounted on an Ally Craft 495 Centre Cabin the Evinrude outperformed the Johno above 4000rpm and returned brilliant performance for a 70 two or four-stroke. Starting instantly, hot or cold, and reaching normal operating temperature very quickly, the motor trolled at a low 700rpm with hardly any vibration transmitted through the aluminium hull. However, there was some harmonic vibration on this hull between 750-1000rpm, but it quickly disappeared over these revs.

Low speed manoeuvrability was such that just engaging forward or reverse gear was enough to control the boat!

Spinning the standard 17-inch pitch Johnson 70 prop and pushing a total of just under 800kg, including two adults, the Evinrude held a clean plane at only 22kmh on 3100rpm.

At 4000rpm, we averaged 35kmh and a quick check of the motor's fuel consumption showed it to be using 9lt/hr at these revs. The Wide Open Throttle (WOT) average was 60kmh on 6200rpm where the engine consumed 20lt/hr. Noise levels at these revs were very low for any 70 and it was quieter than the Johno, while from fast idle up the Evinrude was much smoother than the Johno.

There was some prop ventilation in hard-over figure of eights whereas none occurred with the Johnson, but quickly trimming in the motor cured most of this.

In comparison the Johnson 90, spinning the same pitch prop and pushing 750kg, planed us cleanly at 2800rpm and averaged 41kmh on 4000rpm, where it consumed 12lt/hr. However, at WOT it averaged 53kmh on 5400rpm consuming 29lt/hr.

Considering both the speed and fuel consumption differences, at 4000rpm, the four-stroke returned 14% better fuel efficiency than the two-stroke, while at WOT the efficiency was a whopping 65% better!

Servicing the Evinrude 70 appears straightforward, with the lower cowls splitting in half for complete powerhead access. Although there's a timing belt for the overhead cam instead of the chain drive of the Evinrude 40/50, this has a life expectancy of 800 hours.

Recommended servicing intervals are every 100 operating hours or once a year (also for the waterpump impeller) after the first 20 hours or three months.

In addition to this schedule, I'd recommend changing the engine oil every six months, regardless of how few hours are clocked up.

The Evinrude 70 retails for 17% more than Honda's BF75, but according to OMC Australia the demand still exceeds the supply proof that boaters are willing to pay for cutting-edge technology!

THREE'S COMPANY
When OMC set about creating its LEAP 4 program, or Low Emission Advanced Propulsion 4 Cycle products to comply with the US EPA 2006 exhaust emission stipulations, it didn't do things by halves. As noted above, instead of opting for carbies in its bigger four strokes, it went straight for multipoint fuel-injection.

As with the brilliant 70, OMC again worked with Suzuki to develop its four-stroke 50, a three-cylinder powerplant that outperforms everything else in its horsepower class.

In my mind, the 'Achilles heel' of all the other four-strokes in this horsepower range is their multi-carb designs. For optimum running, the carburettors must be carefully balanced using a set of vacuum gauges. And if you fish high altitude lakes (over 1000m), smaller carbie jets should be installed and the entire tuning process repeated.

Enter OMC's Suzuki-designed and built three cylinder Evinrude 50 with its 70 hp stablemate the most technologically sophisticated four-stroke outboard on the Aussie market.

This powerplant utilises many aspects of the 1970's powerhead. It has 12 valves for efficient breathing and a reasonably deep gear ratio to effectively convert engine torque to thrust at the prop. And because of its multipoint fuel-injection with automatic adjustment of the air/fuel ratio according barometric pressure, it's equally at home at sea level or on alpine lakes. The result is a mid-range four-stroke that simply has no peers!

Fitted to a Stacer 450 runabout, the test motor started instantly, hot or cold, with no oil smoke at any time. Spinning a 14-inch pitch aluminium prop and pushing an estimated total of 800kg (including three adults), the 50 had plenty of bottom end torque for manoeuvring. Its gearshift was smooth and progressive with hardly a clunk, despite the idle being set way too fast at 1000rpm.

Providing the anti-ventilation plate was kept immersed, no cooling water starvation occurred and, at all times, the pilot water discharge was clearly visible. The power trim and tilt worked very quickly, and proved really useful whether backing the boat off the beach or trimming in or out while planing.

Opening the throttle provided smooth, progressive power with no hesitation as is sometimes the case with carbie engines.

The motor planed us at only 23kmh on 3700rpm. The minimum cruising speed was a very quiet 26kmh on 4000rpm.

Above these revs power came in strongly and at WOT (5800rpm) we averaged 47kmh over a blustery windblown chop of up to 30cm high.

Even at this speed, the motor was noticeably quieter (mainly due to reduced induction noise) than I remember both the Honda BF50 and Yamaha F50. The only drawback was some prop ventilation in hard-over figure of eights.

Although there was insufficient time to record any fuel consumption figures, I estimate that at 4000rpm the Evinrude 50 would consume 6-7lt/hr and at WOT about 16.

Apart from the spin-on oil filter, which requires removal of the port lower cowl for changing, servicing appears straightforward. The oil filler cap and level dipstick are easily reached, and the fuel filter is positioned so that any dirt in it is clearly seen. For a twin-cam engine the powerhead is surprisingly compact, helped by the ignition coils being integrated with the spark plugs, motorcycle-style. Servicing intervals are every 100 hours or once a year after the first 20 hours or three months.

Being a premium product, the Evinrude 50 (and 70) is unlikely to be discounted a move even more likely now that Suzuki has withdrawn from the Australian marine marketplace.

At the time of writing, therefore, it is somewhat more expensive than its rivals. For example, the Honda BF50 retails for 17% less.

That said, considering the development work put into the Evinrude 50 and the performance, fuel efficiency and user-friendliness benefits offered over the competition, I believe that if you can afford this motor it is the only way to go!