Suzuki in its DT2 and DT2.2. Not only did
the impeller have a very long service life,
because it rotated only at prop shaft and
not crankshaft rpm, but by removing the
prop and gear case end cap the impeller
could be easily replaced or cleaned without
having to separate the lower unit from the
leg and disconnect the clutch rod linkage.
In line with Tohatsu’s engineering
approach the lower unit held a massive
90 millilitres of oil, whereas some of the
direct drive competition held as little as
35ml. The additional oil capacity meant
that should the prop shaft seal have a
slight leak there was sufficient oil to
prevent gear damage. Plus of course, not
having a clutch, the only moving parts in
the gear case were the pinion and drive
gears. Prop protection was via a traditional
shear pin with the props held in place by a
large cotter pin. Again the engineering in
this area left the competition for dead.
Four trim positions were provided. Early
models needed an 8mm socket wrench
to remove the trim rod nut to reposition
the rod in alternative holes, but later
models used a quick-release rod. Up until
1991 when the paintwork was switched
from blue to grey no tilt support knob
was fitted, meaning the tilt friction nut
had to be tightened firmly. In reality this
method did not hold the leg up on a tender
towed in rough water, so the addition of
the tilt knob was very welcome. A screw-
in steering friction adjuster allowed the
engine to be set in one position when using
it as an auxiliary on a sailing boat.
Whereas the Mercury/Mariner and
Force variants had lift-off cowls, the
Tohatsu models stuck with the original
clamshell cowl design. While this made
for a very compact engine, having to
undo several screws to access the power
head was a pain and, in later years, this
affected the appeal of Tohatsu models. If
the recoil starter failed both halves had to
be removed and the finicky screws could
easily be lost overboard. At least a clip-on
hatch was fitted to access the spark plug.
Because a thermostat was not fitted
in the cooling water passages these were
fairly small to prevent over-cooling under
low loads, such as trolling fishing. As I
found out the hard way when my 1990
model M3.5A was stowed on its side in
the cabin of my 6.7m plywood Bluebird
keelboat, accumulations of aluminium
chloride crystals, commonly mistaken as
salt, would clog these passages resulting45
http://www.mysailing.com.auSPECIFICATIONS
- Engine type: loop charged single cylinder
two stroke - BHP/MHP*: 2.4/2.4 at 4500rpm
- WOT range (rpm): 3800 to 5200
- Piston displacement (cc): 74.6cc
- Bore x stroke: 47 x 43mm
- Gear ratio: 1.85:1
- Dry weight (kg): 12.5
- RRP 2016: $790
- Emissions certification: OEDA "0" stars
*Brake horsepower/metric horsepower or PS
MAIN: On the author’s Fairlite Gull sailing dinghy.
Compact power head.PERFORMANCE
Tohatsu M2.5A and Aqualine F2.5 on 3.8 metre
Fairlite Gull sailing dinghy, total displacement
300kg. Average of two way runs on Lake Macquarie
NSW, calm water. Range is in nautical miles.
Engine M2.5A F2.5
Gear ratio 1.85:1 2.08:1
Prop pitch (in) 5.7" 6"
Fuel capacity (litres) 1.4ll 0.9ll
Trim position 2nd 2nd
Throttle opening trolling trolling
Knots 3.2kn 3.5kn
Rpm 1600 1900
litres per hour 0.2 0.1
nautical mile/litre 16.0 35.0
Decibel at 3 metres 69.7 69.0
Throttle 1/4 1/4
Kn 4.3 4.9
Rpm 2300 3200
l/h 0.3 0.3
nm/litre 14.3 16.3
dB @ 3m 72.6 73.2
Throttle 1/2 1/2
Kn 4.8 6.1
Rpm 2900 4500
l/h 0.5 0.6
nm/l 9.6 10.2
dB @ 3m 77.9 77.5
Throttle WOT WOT
Kn 6.3 6.5
Rpm 4300 5000
l/h 1.3 1.0
nm/l 4.8 6.5
dB @ 3m 87.8 88.2“BUT IF YOU WANT TO LOSE
FLAB THE M2.5A SURE IS
THE RIGHT ENGINE!”