96 | TRADEABOAT.COM.AU

Talking

torque

with

ANDREW NORTON

Three cylinders make all the difference.

BALANCING ACT

hen pondering a manual start 40 it's
essential to consider your ability to
actually start the engine. Sure, some
simple twin cylinder two-strokes are still available

• such as the 696cc Suzuki DT40 and 703cc
  Yamaha Enduro 40 – but unless you've been
  bulking up, these engines are very hard to
  start when cold.
  The trouble is that having two large
  displacement cylinders, even with one piston up
  and one down, creates an imbalance that requires
  a lot of effort to overcome. Add another cylinder,
  however, and the balance is restored to the extent
  that even a two-stroke outboard of over 800cc can
  be started manually without permanent back or
  shoulder injury. Yamaha's 849cc Enduro 60 is
  a prime example.
  Therefore, starting a smaller displacement three
  cylinder outboard, such as the Mercury 40LW (40
  Super, as it's recently been re-named) is no sweat.
  Since 2001 I've tested three of these and each has
  started cold with a firm two-hand pull and only
  one hand is needed when hot.
  The only real complexity with this engine
  is that it has three carbies, whereas the DT40
  and Enduro have one. But providing the carbie
  linkages are kept well lubricated the engine
  should hold its tune between services. In any
  case, because of the way lower compression ratios
  in two-strokes compared to four-strokes having
  three carbies slightly out of tune won't adversely
  affect performance, whereas in four-strokes the
  engine will run like a dog.
  Being de-rated from 50 HP the 40 Super is a

very under stressed engine. It can even cope with

slight over propping as I found out when testing

my first 40 Super.

THE NITTY GRITTY

The Japanese-made 40 Super has the same

cylinder bore as its twin cylinder 30LW

counterpart with a slightly longer piston stroke.

The ignition timing advance is mechanical and

the chokes are manually operated via linkages,

as are the throttle opening flaps for the carbies.

The optional 12 volt, 130 watt alternator has

voltage regulation so it won't fry a battery used

for electronics on long runs to and from favourite

fishing spots.

Power head access is excellent with an easily-

reached bowl type fuel filter and spark plugs.

The break-in period is ten hours on 25:1 before

switching to the normal 50:1 ratio. Providing a

semi-synthetic oil is used, the engine can be run

on either standard (91 RON) or premium (95)

unleaded. Although engine performance won't be

enhanced by using 95 the possibility of using fuel

tainted with ethanol will be reduced.

Six trim positions allow for fine tuning of leg

angle relative to transom rake (I've found the

third position seems the best all rounder) and a

single shallow-water drive setting is provided,

along with a full tilt lock.

Servicing intervals are every 100 running

hours or annually after the first 20 hours/three

months and provided the 40 Super is serviced by

an authorised Mercury Marine service centre the

total warranty coverage is five years.

ON THE WATER

The first 40 Super was mounted on a 4.45

metre Sea Jay Escape 'top ender' style of tinny

and though over propped provided reasonable

performance at or near Wide Open Throttle with

excellent midrange fuel efficiency. On this hull the

demo engine was a bit chuggy below 1,000rpm

but quickly smoothed out above this, and out

to WOT very little vibration was transmitted

through the tiller arm. Like all carbie two-strokes

it became a bit raucous at WOT but when

throttled back was reasonably quiet. Despite being

on a hull with a long deep keel and swinging an

alloy prop, no prop ventilation occurred through

tight figure of eight turns at 4,000rpm.

Next up was a 4.8 metre Kiwi-built Smartwave

4800 polyethylene open dinghy and this time

opting for the standard prop made a world of

difference, with the engine being slightly under

propped and handling the significantly greater

hull displacement much better. All Japanese

outboards love to rev and slight under propping

on planing hulls is always the way to go, especially

when pushing heavier loads.

Most recently was a 4.1 metre Brooker open

tinny. I'd tried this hull in the past with 30

horsepower outboards and the additional power

transformed this hull into a sprint boat. We didn't

have time to do performance trials since we were

using it as a camera boat while photographing

a Force Crossover 26, a review that appeared in

Trade -a-Boat issue 478. Being used to simple

things in life I think I actually enjoyed driving the

Brooker more than the Force 26. The guys who