Talking Torque
quickspecs
Tohatsu MFS5C LPGTYPE Single cylinder four-
stroke LPG outboard
RATED BHP/MHP* 5.0/5.0
at 5500rpm
REC. WOT RANGE 5000 to
6000
DISPLACEMENT 123cc
BORE X STROKE 59 x 45mm
GEAR RATIO 2.15:1
WEIGHT 27.2kg (short shaft)
RRP $2084 (short shaft)
RRP GAS BOTTLE $198
OEDA STARS 3 (plus Euro
Recreational Craft Directive 2
star rating)
*Brake horsepower/metric
horsepowerregulator and about seven
or eight pulls are needed
compared to one or two
for the 6. The engine has
decompression starting
where the exhaust valve is
kept open until the engine
fires so cranking it requires
no more effort than the
Tohatsu MFS3.5. Once the
engine fires progressively
pushing in the enricher knob
allows the engine to settle
down to a low idle with less
vibration than the petrol 6.
Only on cold starting is
there a slight gas smell
but no oil smoke appears.
Tohatsu recommends
warming a cold engine in
neutral for at least three
minutes above five degrees
ambient temperature and
five minutes below. Before
switching off the engine
after each run or flushing I
turn off the gas at the bottle
and the engine runs for 40
seconds on remaining gas in
the fuel line.
Using the third trim hole
and swinging the same
eight inch pitch prop theloan 5 accelerated as quickly
onto the plane as the 6 but
did “lock up” at the lower
end of the recommended
WOT rev range pushing
my standard two adult
and fishing tackle load.
Swapping for a seven pitch
prop allowed the engine to
rev right out to just below
where the rev limiter cuts in
at 6300rpm.
Unlike petrol outboards
where I can connect a fuel
flow meter I could only work
average fuel usage based on
the weight of LPG consumed
and not for specific revs. An
electronic bathroom scales
was used with increments
of 0.1 KG so measuring
was not as accurate as
determining petrol usage in
millilitres. However Tohatsu
states the 5 uses 1.0 KG/
hour at WOT but with the
engine revving out to 6200
running the seven inch prop
the loan engine was really
using around 1.1 KG/hour.
Elgas states 1.0 KG of LPG
equals 1.96 litres so that’s
a WOT consumption of 2.2Lt/h compared to 2.1 for the
petrol MFS6CS, which ran
out to 15.3kts and 5700rpm
swinging the eight inch
prop.
After 2.5 hours of running
with a total of 7.5 percent
WOT operation, averaging
0.7 Lt/h the fuel/oil ratio was
1100:1, not bad for a small
four stroke engine.THE WRAP
Obviously the higher
purchase price of the 5 will
deter some boaters. But it
is an excellent compromise
between a four stroke
petrol outboard and an
electric outboard such as a
Torqeedo. It’s significantly
less expensive and the
7.5 KG gas bottle gives a
much longer range than a
comparable-weight lithium
ion battery. The 5 performs
well on flat bottomed punts
to 3.5 metres without (in
NSW) needing a driver’s
licence or boat registration.
It’s beautifully made and the
crisp white paintwork looks
so good compared to black orgrey outboards. Also it’s safe
for dentures and retaining
hard-earned flab.
If other LPG outboards can
be this good then I feel petrol
for four stroke outboards will
have a limited future. And
the big winner will be the
environment!
The loan 5 and gas bottle
were supplied by Lakeside
Marine, (02) 4392 6110 or
visit http://www.tohatsu.com.au84 tradeaboat.com.au