Trade-A-Boat — January 2018

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torquing


talk
WITH ANDREW NORTON

Two-stroke killer


TOHATSU’S NEW 20E SPORT WAS DESIGNED TO COMPETE DIRECTLY
WITH TWO-STROKES...

T


he biggest
problem with
four-strokes so
far has been
their weight
compared to two-strokes.
Fine if the hull is designed
to take the weight but not
so good when re-powering
older hulls that were never
designed for the higher
transom weight. Not to
mention the extra stresses
on older trailers aft of the
axle(s).
Tohatsu has been working
steadily to reduce the weight
of its midrange four-strokes
so they compare directly
with two-strokes. The MFS
40A and 50A released a
few years ago are prime
examples and the new 20E
Sport is the next stage of
development. Currently it’s
the lightest four-stroke 20
on the Aussie market.

By reducing the
piston displacement, leg
dimensions and opting for
a plastic engine pan the
20E is a full 8.5kg or 17 per
cent lighter than its 20D
predecessor, yet through
using EFI actually produces
more torque. The 20E is only
2kg or five per cent heavier
than its long running two-
stroke M18E2 counterpart
(Trade A Boat, issue 496) so
can safely be mounted on
older tinnies such as the
3.8m Savage Snipe dinghy.

THE NITTY GRITTY
The carbie 20D displaced
351cc with a cylinder bore
of 61mm and piston stroke
of 60 whereas the 20E has
the same bore but a shorter
stroke, resulting in a five
per cent smaller piston
displacement. Apart from
this the new power head

still has decompression
starting and two valves
per cylinder actuated by a
single belt-driven overhead
camshaft. Fortunately the
engine is non-interference
so that if the belt breaks
the pistons won’t contact
the valves. It develops a
whopping 26Nm of torque
at 4500rpm compared to
25.5 at the same revs for the
carbie 20D.
Unlike the M18E the
ignition has electronic
timing advance and the ECU
(Electronic Control Unit)
automatically reduces revs
to 2800 should the engine
overheat or suff er low oil
pressure. The rev limiter is
set at 6300rpm which we
experienced during initial
trials before swapping to a
larger pitch prop.
Servicing intervals are
every 100 hours or six

months after the initial
20-hour service. A large
capacity canister oil filter
is fitted with a clever drain
hose ensuring any oil that
escapes the filter during
removal is captured when
the engine is fully tilted. A
range of oils may be used
but the recommended oil is
Quicksilver FCW SAE 10W30,
which can handle ambient
temperatures to over 40
degrees. With oil filter
change the sump capacity
is a reasonable 1.2lt so any
dilution during extended
trolling periods shouldn’t be
an issue.
The plastic engine pan
can be split for full power
head access though
removing the rocker cover
to check valve clearances
is straightforward. Steering
friction is easily adjusted
using a horizontal lever

94 tradeaboat.com.au
Free download pdf