Trade-A-Boat — January 2018

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