Johnson 6hp turns 40

Developed in late 1964 to replace the bulky Johnson 5.5hp, the 145cc 6hp became one of OMC's all-time favourite models.

In 1965 my father bought one for his 12ft dinghy to access our family weekender on Scotland Island on Sydney's Pittwater, and during the two years he owned it the reliability was second to none. Apart from a deeper gear-ratio gearcase, the 6hp remained virtually unchanged through to 1978 when Capacitor Discharge (CD) ignition replaced the twin contact breaker points.

But in 1980 OMC "stroked" the engine to 164cc to create a 7.5hp, which was manufactured through to 1984 when the company released 6hp and 8hp versions of this engine, the latter gaining the additional output mainly through a tuned exhaust gas megaphone. The 6hp and 8hp were continued through to late 1990.

In the current model released in early 1991, OMC swapped the Bendix recoil starter for an overhead unit and relocated the sparkplugs to the centre of the cylinder head. It also swapped the side-mount gearshift and tiller arm for a centre-mount gearshift and tiller arm, creating a much more user-friendly engine. A fold-down carry handle was also fitted between the transom brackets.

In 1990 I borrowed both the 6hp and 8hp from OMC Australia for three months and "lived" with the de-rated 5hp version of the 6hp through 1992, and the up-rated 8hp through 1993. All the engines I borrowed had both excellent reliability and very good saltwater corrosion resistance, with no corrosion apparent after more than 100 hours of leg/lower unit immersion.

The reason for the popularity of these engines was their inherent good engine balance due to the twin-cylinder crossflow-scavenged design. OMC always made good crossflow engines, and the ease of servicing and relatively cheap and readily available spare parts made owning one a pleasure.

Fortunately, new Johnson owner Bombardier Recreational Products has retained the 6hp and 8hp, and for anglers who use their outboards infrequently and only in saltwater, these models are still outstanding value for money.

Tested on my 3.6m Sea-Al dinghy, both engines provided more than adequate power, with the 8hp having a significant performance edge - but at the expense of fuel efficiency. Both engines had the standard 9in prop and pushed a total of 285kg including two adults and fishing tackle (see performance table).

Both engines started easily hot or cold and had low vibration levels matched only by the much heavier crossflow Mariner/Mercury 6/8hp, both de-rated from a 9.9hp.

Although both engines have shear-pin prop protection, the pin is located aft of the prop and is very easy to replace. Servicing the 6/8hp is straightforward, with the sparkplugs, ignition timing advance linkages and screen-type fuel filter easily reached.

The recommended servicing intervals are every 100 hours or once a year after the first 20 hours or three months, and the waterpump impeller should be replaced every 100 hours.

Bombardier's non-declining warranty provides two years of coverage for these engines.