out in the top end, needing
a smaller prop to achieve
similar Wide Open Throttle
performance.
THE NITTY GRITTY
The power head has a gear-
driven camshaft operating
push rods and rockers to
actuate the two overhead
valves. Full pressure
lubrication is provided with
an oil level warning light on
the engine pan. An effective
thermostat helps warm the
engine quickly from cold
and maintain reasonably
constant operating
temperatures.
A five amp alternator
is optional and Tohatsu
recommends a 12 volt 40
amp/hour 350 CCA (cold
cranking amps) battery for
temperate climates and a
70 amp/hour 650 CCA unit
for cold climates to prevent
frying the battery on long
runs to and from a favourite
fishing spot.
Like the 6 there are six
trim positions, a single
shallow water drive setting
and automatic full tilt and
reverse locks. Again the
engine must be in forward
gear to tilt, a pain when
setting shallow water drive.
In the 5 the fuel pump is
replaced with a regulator
which needs to be supplied
with at least 1 bar or 14.7psi
of gas from the bottle. A
shut-off valve stops gas
flow whenever the engine
is stopped. The carbie is
replaced with a mixer,
which looks like a carbie
except there’s no fuel bowl.
And finally valve seats
are hardened as unlike
petrol, LPG is a dry and
hotter burning fuel and
provides absolutely no seatlubrication.
However there is an
air/gas enricher just like
a choke which must be
pulled out when starting
a cold engine and slowly
pushed in as it warms. The
7.5kg capacity Sprint Gas
fibreglass bottle supplied
was well made with marine-
grade brass fittings and the
translucent cylinder showed
the liquid gas level below
half capacity.
Servicing intervals are
every 50 hours or annually
after the first 20 hours.
Valve clearance adjustments
aren’t needed for the first
200 running hours and
removing the rocker cap to
adjust clearances is easy.
The 0.45lt sump is a
little light on capacity to
absorb oil sludging between
changes. But being a gas
engine it’s unlikely there’llbe the same blow-by issues
that afflict petrol engines
during extended trolling
periods. A large drain
elbow under the sump
makes changing oil easy.
Tohatsu recommends using
Quicksilver FCW SAE10W30
for all-round use.
The recreational usage
warranty is three years.ON THE WATER
The fully run-in loan 5 was
an almost perfect match for
my 2003 Sea Jay 3.4 Punt
and outperformed a two
stroke Tohatsu M5B under
identical test conditions,
though it needed a finer
pitch prop to reach the top
end of the recommended
WOT rev range.
Cold starting isn’t as easy
as the 6 as there’s no fuel
primer bulb so it takes a
while for gas to reach thewant more?
Head over to
tradeboats.com.au to read
more of Andrew’s reviews.
“If other LPG outboards can be this good
then I feel petrol for four stroke outboards
will have a limited future.”
tradeboats.com.au 83