46
Cruising Helmsman July 2018PRACTICAL
ENGINES
in occasional cylinder head removal to
clear out the deposits. Removing the
cylinder head is not easy because it is also
the cradle for the fuel tank, so some major
disassembly is required. So if you do not
have access to a f lushing drum after using
the engine in saltwater it should always be
stowed upright to allow all water to drain
from the cooling passages.
Servicing intervals have reduced since
the release of the M2.5A. Initially they
were 50 hours or every six months after
the first ten hours or one month, but in
the past decade intervals have changed to
every 100 running hours or annually after
the first 20 hours or three months. The
M2.5A paintwork was changed from grey
to the current indigo in 2005.GETTING TO KNOW THE M2.5A
More of a re-acquaintance really.
I had borrowed 1989 and 1996 models
but had not tried an M2.5A since then.
Unbelievably, Lakeside Marine the
national Tohatsu distributor, found a 2008
model engine lying unused in its original
shipping box. What a slumber for the last
new M2.5A in Oz!
Lakeside’s Trevor Robinson checked
the gear oil level, fitted a new spark plug,
added a 25:1 mix of premium 95 and semi-
synthetic Valvoline outboard oil, filled the
test tank and IT fired up on the first pull.
Since picking up the engine I have run
it on exactly the same fuel mix as, being
an old fart, I do not think five hours on
25:1 are enough. I figure ten hours are
better which approach fast.I guess it was because I had already
borrowed two M2.5A and three M3.5A
models that I ended up with five of the
six prop choices. The standard 5.7" pitch
F6 prop was perfect for my 2003 Sea Jay
3.4 punt and 1981 3.8 metre Fairlite Gull
sailing dinghy. But I had also retained
the 4.3" prop used for pushing my Bluey.
This was perfect for my mate Richard
Ardizzone’s Walker Bay 10 sailing dinghy
as the standard F6 had way too coarse
a pitch for this short waterline hull.
On the three hulls the loan M2.5A
normally started first pull hot or cold
but, with the carbie jet set lean, required
at least 30 seconds of choke to keep
running when cold. Even on 25:1 oil smoke
emissions were low with only a faint oil
smell in following seas.
All running in was done on the Sea Jay
with no WOT operation until the first
five hours had been clocked up. Vibration
levels during the first two hours were
high enough to give my tiller arm f lab
a real workout and rattled the steering
friction adjuster overboard to a new life
perplexing bottom feeding fish. So we
lashed the carry handle to the hull to
prevent the engine from swivelling 180
degrees when tilted. On the 15" transom
and set on the second trim hole the M2.5A
could be swivelled 180 degrees for reverse.
From two to five hours vibration levels
reduced but remained nowhere near as low
as the four stroke Aqualine F2.5, reviewed
in Cruising Helmsman last year, that I had
been testing since May 2017.
Next up was the Fairlite Gull. The
relatively long waterline length of thisPERFORMANCE
Tohatsu M2.5A and Suzuki DF2.5 on Walker
Bay 10 sailing dinghy, total displacement
270kg. Average two way runs on Lake
Macquarie NSW, calm water. Range is in
nautical miles.
Engine M2.5A DF2.5
Gear ratio 1.85:1 2.15:1
Prop (in) 4.3" 4.5"
Fuel capacity (litres) 1.4l 0.9l
Trim position 3rd 3rd
Throttle trolling trolling
Knots 2.6kn 2.0kn
Rpm 1600 1500
l/h 0.2 0.1
nm/litre 13.0 20.0
Throttle 1/2 1/2
Kn 4.6 5.0
Rpm 3400 4400
l/h 0.7 0.6
nm/l 6.6 8.3
Throttle WOT WOT
Kn 5.4 5.6
Rpm 4500 5400
l/h 1.4 0.9
nm/l 3.9 6.2ABOVE LEFT AND
RIGHT: Set up on
the Walker Bay 10.