Listerparts.co.uk.
The Lister 2G Marine Gearbox is most commonly found on
two and three cylinder marine versions of the Lister H Series engines;
HA, HR, HRW, HW.
It is also fitted to the rather more scarce FR Series
two and three cylinder marine engines, although whether it was called
2G at that point is not clear.
It is a little unusual compared to many marine boxes
of the time in so far as it is close coupled to the timing gear end of
the engine, at the opposite
end to the flywheel. The gearbox is mounted on a
dedicated housing which replaces the tin gear end cover of most
non-marine engines. If
contemplating fitting a 2G box to an engine not
previously equipped with one, it is essential to have all the correct
pieces.
The 2G was available as a direct drive unit or with a
reduction box of 2:1 or 3:1 ratio. The photograph shows a
reduction box fitted. It is
important to note that it is not readily possible to
convert between direct drive and reduction drive in an existing
installation as there is a difference in height of several inches in
the output flange.. Otherwise, conversion is relatively simple.
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Lister 2G -- How it works:
The 2G is a relatively simple, three position
gearbox: Forward, Neutral, Reverse. Power is transmitted
to the gearbox from the engine by a deep gear
with a drilled centre. The gear is secured to the
nose of the crankshaft with studs and nuts and the end of the crank is
drilled to allow the passage of
engine oil under pressure to lubricate the
gearbox. There is no drive plate between the engine and gearbox.
The input gear mates with
a set of internal epicyclic gears which are part of
the gearbox drum and hub assembly. In neutral with the engine running,
the hub assembly spins but no drive
is transmitted. When forward is selected, a pair of
toggle levers are pushed over centre, acting on a carrier which pushes
together a multi plate clutch.
The clutch discs have serrated edges which are
permanently in contact with serrations on the inside of the hub; the
end pressure plate is keyed to the
mainshaft. With the clutch discs pushed together,
drive is transmitted.
To obtain neutral from forward, the toggle levers are
pulled back over centre in the opposite direction, removing the
pressure from the clutch discs
which are then able to spin relative to the pressure
plate -- no drive being transmitted.
Reverse is achieved by the action of a brake band
gripping the outer face of the hub/drum assembly. With the drum unable
to turn, the epicyclic gear train comes into play, transmitting drive
in the reverse direction via a gear on the forward end of the
mainshaft.
Forward and neutral are actuated by an internal forked
lever operated by a gear selector cross shaft. Reverse is actuated by
a lever, roller and rocker arrangement, also operated by the selector
cross shaft. All these actions are performed by using an external,
manually operated lever. The external lever
has its own external limit and detent bracket which
limits its travel when selecting forward or reverse and gives a
positive centre location for neutral.
It is common for these boxes to be controlled
remotely. Whatever means is chosen to achieve this it is essential to
confirm full and positive engagement
of the desired position. Lister offered a hydraulic
servo kit for operation of the box but this is a vanishingly scarce
option that we have seen just once.
In either the direct drive version or the reduction
box version, a thrust bearing is fitted immediately behind the output
flange capable of taking all forward or reverse thrust.
What are the common problems ?
The good news is that generally
these are not a problematic gearbox, but inevitably age and use will
catch up with them, so watch out for ---
Any sign of slipping, either in
forward or reverse. The relevant adjustment should be checked as
soon as possible.
If adjusting the forward
engagement, be sure to get the toggle screws as even as possible.
Satisfactory adjustment of the
reverse brake band can be difficult as often there seems to be
insufficient scope to let the roller get to where it need to be.
It seems to vary from box to
box; we suspect machining tolerances may have left something to be
desired.
Not a common failing, but
not unknown; the brake band metal can completely fracture.
Replacement is the only fix.
Still with the reverse band, it
is also not unknown for the post that carries the actuating rocker
to pull its studs from the gearbox casing.
However you choose to fix this,
do it well or you will be doing it often (if you use reverse).
General wear is the next most prevalent issue,
including worn bearings, bushes, gears and sometimes the hub/ drum
itself. The good news is unless left to an extreme condition, none of these things will rob you of drive. A
useful and simple test is to grasp the output flange (with whatever
it is coupled to unbolted) and check for any lateral movement or evident rotational noise or roughness when
turning by hand in neutral. Readily perceptible lateral movement,
noise and roughness almost inevitably indicate a box in need of some renovation.
Bear in mind however that the gearbox is pressure
lubricated from the engine oil circuit, so worn bushes along the
mainshaft will leech away main engine oil pressure as surely as wear
in the engine itself. As they share the same oil, any contaminants
arising from the engine will find their way into the
gearbox and vice versa.
Things to do and not to do:
DO --
Adhere
to the engine oil and filter change intervals.
Remember
that where a reduction box is fitted, this does NOT
share the engine oil. It uses SAE80 or SAE90 gar oil and the level
should be checked using the dipstick.
Make sure the engine installation is such that the gearbox output
flange and whatever is connected to it are perfectly aligned. The
flanges should be perfectly flat to each other and the bolts go
through their holes, by hand, fully. Misalignment here will cause
premature wear to the gearbox and likely
the stern gear. Flexible propshaft couplers are
no substitute for basic correct alignment, unless they are a properly
engineered double jointed assembly, using a separate thrust plate.
If the engine appears to be labouring and / or black smoking. With the
engine turned off and the gearbox set in neutral, check that the
propshaft rotates freely. If not, check for a fouled
propeller. Make sure no one can start the engine or engage a
gear while you are doing this.
DON'T --
Try and free a fouled propeller by constantly
alternating between forward and reverse. If a good blast in reverse
does not clear the prop, best to
physically remove whatever is causing the
problem.
Leave the gearbox in gear if you are not using the
boat for some time. If you go to your boat but are not moving it, it
is a good idea to start the engine and run the box through its
positions to keep things free in the box.
Make any adjustments to the gearbox selector rollers
unless there is a good reason. Any signs of slippage in forward or
reverse should be
investigated
quickly, but otherwise ---- if it's not broken, don't fix it.
Use any additives in the engine oil. As the engine
and gearbox share the same oil, the additives may glaze the linings,
causing permanent loss of drive.
Fire the engine up with the gearbox removed.
Throw away your old Lister gearbox if you are swapping it out for
something different. Give us a call.
his page is the property of
Listerparts.co.uk. No reproduction without prior approval and
visible credit
Parts Availability.
With the exception of the bearings and
seals, every other part of the gearbox is a Lister specific item and
the majority have not been supported for some
time. We keep stock of the clutch friction discs and brake bands plus
bearings, bushes, seals and gaskets. We also stock core unit
gearboxes and reduction boxes for full reconditioning.
If you are shopping around for bearings, you need to be aware there is
a dramatic difference in quality between those from a reputable
manufacturer and those (typically) of Chinese origin. Some of
the bearings are significantly expensive, but given the work involved
in a rebuild and the effort of removal and refitting it is an area
where it is absolutely not worth economising. As a rule of
thumb, if the bearings aren't made in Europe, Japan or North America,
you probably don't want them.
Top Tip !
We all like a bargain and if your box is playing up you may be
inclined to find a usable second hand unit. Just remember that
the
youngest of these boxes is likely to be pushing 40 years old, so you
do need to be sure before buying that your prospective purchase
actually works.
If it is being sold as rebuilt or having had attention, don't be
afraid to ask to see the receipt as evidence of what has been done.