Johnson 4 (1991 - 2000)

A Johnson classic

When my fishing partner Diann and I acquired a 1981 3.8-metre Fairlite Gull sailing, rowing and fishing dinghy in January, it came with a 1993 Johnson 4 outboard.

Despite having already had a hard life on the NSW Central Coast where Stage 4 water restrictions prevented regular freshwater flushing of the engine, the Johno was still in very good condition. All we had to do was syphon out the stale fuel from the integral tank and replace it with ULP and Bombardier XD50 oil, and in my flushing drum, the engine roared into life on the third pull.

While running the Johno I had forgotten what a "sweet" engine it was. Because of its twin-cylinder powerhead, it was extremely easy to start and had very low vibration levels compared to the single-cylinder Japanese-origin fours currently available.

Since 1973 I have owned two Johnson 4s and borrowed four of them for long-term evaluation, so I have seen the evolution of the engine over the years until it was discontinued in 2000.

CONCEPT AND DEVELOPMENT
The Johnson 4 was unique in the recreational boating industry in that it was the smallest twin-cylinder outboard ever produced. Its original design dates back to 1952 when it was released as the Johnson 3 with the "Protecto Drive", a down angled lower unit having a full skeg to protect the prop in shallow, stump-filled waterways. A conventional right-angle drive lower unit was added in 1964, but the egg-shaped cowling design was retained. The 3 developed 3.0 flywheel horsepower at 4000rpm.

In 1969 the 3 was upgraded to 4.0hp (at 4500rpm) utilising the leg and lower unit from the discontinued Johnson 5, a direct-drive version of the legendary Johno 6. The clamshell cowls were swapped for a pan-style lower unit and moulded fibreglass upper cowl with a side-mounted recoil starter. The throttle was moved to the side and a tote tank was standard.

The 1970 model I owned was used as an auxiliary on my 7.6m yacht and normally started first pull hot or cold, providing it had not been left unused for a while as the twin ignition points suffered from dampness in the salty environment. But once running, it never missed a beat and pushed the 1.6-tonne hull to 8.9kmh.

Unfortunately OMC replaced this model with the Euro 4 version having a clamshell cowling, forward-mounted throttle lever and integral fuel tank. This model was known in the UK as the "You row 4" because of its ability to easily overheat. At least in 1981 the Johno was fitted with a clutch, a strange spring-type system that was located aft of the propshaft drivegear, which was still behind the pinion gear, resulting in a left-hand prop instead of the competitors' right-handers.

MAKING THE 4 COMPETITIVE
In late 1985 OMC released the Saddle Tank (Ultra) Johnson 4, which still had a clamshell cowling, but electronic ignition and a cleverly-designed 3.785lt plastic fuel tank that clipped around the leg. The throttle control was relocated atop the engine and a stop button fitted to the end of the tiller arm. Fortunately the Euro 4 was dropped for the Australian market and because the ICOMIA 28/83 directive stated that all outboards had to be prop rated, this Johno developed 4.0hp at 5000rpm. In normal recreational boating it also used a 100:1 premix, although OMC reverted back to 50:1 four years later.

In 1986 I borrowed a Saddle Tank 4 from OMC Australia, which I soon purchased and tested for five years. The engine never missed a beat, although it did have some corrosion problems.

For the Aussie market, OMC sourced the Johnson 4 from its Belgium plant from late 1990 onwards, when the Bankstown, Sydney, plant was closed. This model 4 remained virtually unchanged until 2000.

In October 1990 I borrowed the first of four of these engines over a 10-year period. The clamshell cowling had been replaced by a removable upper cowl and a lower cowl that split in half for full powerhead access. The innovative but potentially troublesome cold-start fuel primer of the Saddle Tank 4 was replaced by a conventional choke and the Saddle Tank dropped in favour of integral or remote fuel tanks. A twist-grip throttle replaced the slide control and the stop button was relocated to the control panel on the lower cowl. A pilot water discharge was fitted and the exhaust relief holes moved up to under the powerhead to reduce exhaust gas backpressure.

Engine performance had improved significantly and the longshaft auxiliary version I borrowed in 1991 pushed my 6.7m 1.7-tonne Bluebird yacht to 11.4kmh. This Johno was completely reliable over a six-month evaluation period.

In February 1993, I evaluated the reliability of the shortshaft version for OMC. Over this period the engine clocked-up 201.5 hours and with a total of five per cent WOT operation averaged 0.7lt/h. To maintain a minimum operating temperature of 38ºC, despite a thermostat not being fitted, OMC had swapped the six-vane waterpump impeller to a three-vane unit, resulting in the engine being able to troll for up to six hours without stalling or fouling its spark plugs. Yet the impeller was still capable of supplying enough water to maintain the maximum operating temperature under 73°C.

When the impeller was removed at the 100-hour service, my local dealer and I re-installed it for another 100 hours. At 200 hours there was hardly any wear on the vane tips and at this service the clutch spring was undamaged. The engine was completely reliable, but there were corrosion issues.

However, by the late '90s the build quality had fallen-off and the 4 I borrowed in January 2000 wasn't a patch on the 1993 model for performance and reliability.

PERFORMANCE & EFFICIENCY
With its twin-cylinder crossflow powerhead the 4 never delivered the fuel efficiency of its Japanese competition, although it was much lighter.

Mounted on my 3.0m deHavilland John 10 punt, spinning a seven-inch plastic prop and pushing a total of 235kg, including two adults and fishing tackle, the 1993 Johnson 4 trolled at 3.0kmh and 850rpm using 0.38lt/h. The WOT averages were 13.6kmh and 4680rpm using 2.45lt/h, and across a "loop" of 10 per cent WOT and 40 per cent trolling averaging 7.5kmh, the Johno used 1.2lt/h.

When the total displacement was reduced to 180kg, the Johno reached 27.0kmh and 5760rpm, because the torque of the twin-cylinder powerhead was sufficient to overcome the planing hump.

The nearest Japanese outboard for performance is Yamaha's crossflow single-cylinder 4A, and at 82.5cc, has the smallest piston displacement of all current-model fours. It does have a full gearshift but at 21kg, this engine is 40 per cent heavier.

SERVICING AND PRICING
Powerhead access of the 1991 to 2000 Johnson models is very good and servicing intervals are every 100 hours.

Both the Saddle Tank and 1993 Johnos needed a new driveshaft at 100 hours due to corrosion at the gearcase seal, just beneath the waterpump impeller. Also, due to a small gap around the idle-speed adjustment knob atop the cowls, salt spray reached the recoil starter spring of the Saddle Tank 4 corroding it and necessitating replacement at 100 hours.

Although the propshaft is stainless steel, the end cap is prone to rusting and when this occurs, the slot for the prop's cotter pin starts to close over, making fitting of the flimsy pin very difficult. However, after a total of 220 hours of saltwater leg/lower unit immersion no other corrosion was apparent on the 1993 model.

These comments aside, Johnson 4s made in the '90s have better saltwater corrosion resistance than comparable-age Japanese outboards and because the powerhead was available for so long, spare parts are generally not a problem.

When it was discontinued the Johno retailed for $1460 and a 2000-model is now worth around $800. Expect to pay about $500 for a 1991 model and 200 to $300 for a 1986 model. Frankly, I wouldn't bother buying a Euro 4!