Mid Range Marvels

Many people believe that engines in the 40-50hp range are the most versatile of all outboards. Singularly and rigged as twins, they power the majority of small family trailerboats both aluminium and fibreglass. They are often chosen as workhorses in commercial applications and though the situation is changing, tend to be relatively simple, (dare we say it?) low-tech powerplants.

As such, they are affordable to buy and relatively cheap to operate and service. One added advantage, often not considered, is that powerplants this size can be handstarted without too much effort in the event of a flat battery.

Like all capacity classes, there are stand-out powerplants in the 40-50hp range which are well worth a close look. Here's a rundown of my favourites...

TWO-STROKES
Apart from Suzuki's relatively simple DT40C, all others in this listing are three-cylinder, three carburettor motors.

One comes with the option of manual petrol/oil mixing instead of variable ratio oil injection.

Suzuki DT40C
Released locally in 1985, this 696cc twin has only one carbie and standard oil injection that varies from 50-120:1. It features a built-in overhead recoil starter something lacking in all the other electric-start motors and has a weight of 82kg.

Several years ago I lived with a DT40C for three months and it proved completely reliable. Mounted on a 4.3m Stessl runabout two-up, it wound out to 56kmh and cruised effortlessly at 39kmh at 4000rpm consuming 7.5lt/h. Over a mix of some wide open throttle (WOT) operation and normal cruising, it consumed a very reasonable 5.3lt/h.

The only drawback of this motor is that it's a large displacement twin and as such has relatively high vibration levels below 2000rpm. For this reason, I don't recommend buying one if you do a lot of dead slow troll (DST) operation.

Saltwater corrosion resistance is very good and the loan motor still appeared in showroom condition on completion of testing.

Tohatsu M40D2
Released locally in 1990, this 697cc three-cylinder, three-carbie looper has oil-injection that varies from 50-100:1. The weight is around 80kg.

The Tohatsu starts easily hot or cold, performs very well on tinnies to 4.5m and trolls smoothly as only a three-cylinder 40 can.

On a 4.3m Quintrex Fishabout two-up, the loan motor wound out to around 60kmh and cruised quietly at 40kmh, consuming slightly less fuel than the Suzuki DT40C.

Servicing is straightforward and now that Tohatsu Corporation has solved its paint adherence problems there's no reason why this motor should not stand up to saltwater as well as its direct Yamaha competition.

Yamaha 40
This is the motor that started the 40-50hp three-cylinder revolution in the mid-'80s and its 100:1 premix version has been a favourite among Hawkesbury River (NSW) oystermen for well over a decade.

Like the Tohatsu, it's a three-cylinder, three-carbie looper, but in oil injection form the ratio varies from 50:1 down to only 200:1 at DST. In manual start, premix form the motor weighs 70kg, with the power tilt and trim version weighing 87kg.

Though I haven't had the chance to try the power tilt and trim version, the manual start, manual trim premix model proved particularly torquey on both a 4.3m Quintrex Hornet and 6.8m Yamaha Southwind UB23. In fact, it had no trouble planing a six-adult load on the Southwind!

On tinnies expect similar performance and fuel consumption to the Tohatsu. And of course, Yamaha's saltwater corrosion resistance is second to none.

Mercury 50
Released in late '97, this three-cylinder, three-carbie unit forms the middle engine in Mercury's loop-charged 40-60hp trio. At 967cc it has the biggest piston displacement of all 40-50hp outboards two or four-stroke and could therefore be the most understressed engine in its class, though at 93kg it's a fair lump of a 50. The oil injection ratio varies from 50-100:1.

Mounted on a Quintrex Freedom Bowrider and pushing a four-adult load, the demo 50 wound out to 45kmh and cruised effortlessly at 26kmh at 4200rpm, consuming 10lt/h. At DST the motor was so smooth no vibration could be felt from the helm and there was no clunk when forward or reverse were engaged.

Servicing is remarkably straightforward for a motor that has an undercowl oil tank and the paint finish is the best in the business. Saltwater corrosion resistance is comparable to Yamaha products.

FOUR-STROKES
Though Suzuki has a 40hp four-stroke planned for release in November, there was little detailed information available as we went to press. What is known is that the engine is a 900cc-plus 12-valve three-cylinder version of the brilliant four-cylinder EFI 60/70 released earlier this year.

It's bound to be worth a look and will be marketed under both the Suzuki and Evinrude banners...

Yamaha F50B
The 'bigfoot' version of the F50A, this SOHC crossflow motor suits planing hulls and workboats to 5.8m, displaces 935cc and weighs 112kg with standard PT&T.

Though its four carbies require careful setting up for best performance, once correctly tuned, the F50B is beautifully smooth and will DST for hours without missing a beat. It starts instantly hot or cold and with its massive 2.33:1 gear ratio, it's great for manoeuvring heavier hulls.

On a Yamaha Southwind UB580 workboat two-up, it wound out to 48kmh consuming 18lt/h about 20% less than a two- stroke 50. It cruised unobtrusively at 39kmh consuming 11lt/h and when trolling averaged about 1lt/h!

Servicing is straightforward despite its four cylinders and saltwater corrosion resistance is better than its direct competition.

Honda BF40
A de-rated version of the BF50, Honda's three-cylinder, three-carbie crossflow SOHC engine displaces 808cc and weighs an estimated 100kg in power tilt and trim form.

This engine's powerhead forms the basis of the Yanmar 27hp diesel outboard which has proven very reliable in commercial applications.

Released locally in 1993 in 35 and 45hp models, it's proven popular with boaters looking for a cleaner-running alternative to the relatively 'dirty' two-strokes.

Though fairly heavy for its output, the BF40 suits runabouts to 4.5m and seemed well matched to the 4.0m Webster Twinfisher test hull. Two-up, it wound out to 43kmh and cruised effortlessly at 33 with no speed lost when pushed into a stiff headwind and half-metre chop.

Vibration levels are low and when correctly tuned, you can hardly feel the engine running at DST.