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TALKINGTORQUE
with
ANDREW NORTONTohatsu’s battery-less EFI 30 has now been around 13 years
LUCKY THIRTEEN
hen Tohatsu Marine Corporation
released its first four-stroke outboard
that didn't need an external battery
to run its EFI system, it created a cascade of
followers, starting with Mercury then Suzuki and
finally Yamaha.
By utilising a self contained EFI system
TMC was able to offer a manual start 30 that
didn't suffer from the frequent balancing of
multi carbies as with its MFS 30A predecessor
and Honda's BF30. Gone was the need for a
vacuum gauge to get the balance right, replaced
by a system with plug-in diagnostic capability.
Like the diagnostics used in Tohatsu TLDI DFI
engines, the tachometer showed a possible 28
faults by differing combinations of three lights,
eliminating the need for a laptop computer.
The result was the MFS 30B, which has since
been upgraded to the 30C. TMC also released a
25 HP version of this engine, which is intended
more for commercial applications as it develops
maximum torque at only 3,600 rpm compared to
5,200 for the 30. So the 30 needs to be propped
correctly for application to rev out to just below
the rev limiter set at 6,500 rpm.
THE NITTY GRITTY
With a seven per cent larger piston displacement
than the 30A the 30B/C developed more torque
while actually using less fuel under light to
moderate load conditions. Unlike carbies which
have just two sets of air/fuel ratios (idle and main
jets) EFI either pours in the fuel under load or
reduces supply under light loads. In the demo
30, once the hull was planing cleanly and engine
load was reduced the midrange fuel efficiency was
excellent for a 30.
The cylinder bore and piston stroke of the
30 are the same as the twin cylinder single
carbie Tohatsu MFS 20D, which has since been
replaced by the MFS 20E, an EFI engine that has
a smaller piston displacement. Having common
rings, pistons and con rods is great for reducing
manufacturing costs and increasing spares
availability in remote areas.
The 30's three cylinder power head has
six valves belt-driven from a single overhead
camshaft. The engine is a non-interference
design so that if the belt breaks the pistons
won't contact the valves. However, providing the
belt is replaced about every 800 running hours
and checked annually for any fraying or other
damage breakage shouldn't occur. Valve clearance
adjustment is straightforward.
Included in the engine protection system is
low oil pressure revs reduction to 2,800 to at least
provide a limp-home facility. The EFI has a water
cooled fuel rail to help maintain fuel density
before it reaches the injectors and each spark plug
has its own compact ignition coil that doesn't
interfere with plug access. The voltage regulated
alternator pumps out up to 15 amps and won't
“fry” the starter battery on long runs to and from
a favourite fishing spot.
The oil sump capacity is a reasonably large
1.8 litres with excellent dipstick and oil filleraccess. The side-mounted canister oil filter is
large in relation to sump capacity and bigger in
diameter than some automotive engine filters
used in modern SUVs (the 2.5 litre Nissan
X-Trail engine oil filter is a prime example). The
combination of good sump capacity relative to
piston displacement plus the filter size will help
ensure the sump oil absorbs “sludging” that occurs
from combustion chamber gas blow by past the
piston rings during extended trolling periods.
This is a common problem with water cooled
four stroke outboards that overall run way colder
than automotive engines and between oil and
filter changes the oil level actually appears to rise,
which is due to oil dilution with unburned fuel.
My recommended oil for temperate climates
is Quicksilver FCW (four cycle water cooled)
SAE 10W30, which I've been using in my own
four stroke outboards for 15 years and which
maintains its original honey colour between oil
and filter changes.
The 30C has a deeper gear ratio than the B
model, enabling coarser pitch props to be fitted
for improved thrust efficiency. Whereas the B
model I tested swung a 10-inch pitch alloy prop
to suit its 1.92:1 gear ratio straight from the 30A,
opting for the 11-inch prop on the 30C would
suit heavier planing hulls while the standard 12-
inch prop suits lighter hulls. Like all current four
stroke outboards the 30 needs to rev well out to
develop its rated power.
Recommended servicing intervals are every
100 hours or annually after the first 20 hours or