Lister LM100 -- How it works:
The LM100 is a relatively simple, three position
gearbox: Forward, Neutral, Reverse. Power is transmitted
to the gearbox from the engine by a solid shaft,
bolted to the engine flywheel and with a set of gear
teeth cut at the gearbox end. There is no drive plate between
the engine and gearbox. The shaft 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 spring
pack on the mainshaft pushes a clutch cone into engagement with the
tapered internal face of the drum. As the
clutch cone is splined to the mainshaft, once it
engages, the motion of the hub / drum assembly is transmitted to the
To obtain neutral from forward, a thrust bearing
pulls back on the clutch cone, disengaging it from the drum.
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.
All three positions are obtained by the action of a
pair of rollers acting on profiled levers. The reverse brake
band has a natural springiness to the disengaged
position, plus an additional retraction spring.
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 ?
We see quite a lot of these
boxes and by some margin the most common issues are loss of
reverse; loss of forward; inability to obtain neutral,
by engine stalling if reverse
Loss of forward.
Original cones had rivetted linings and in older boxes these
linings may start to break up simply due to age, or be worn beyond
Loss of neutral / engine
stalling. This is closely related to the issue above, of
linings breaking up. If a piece of broken lining wedges between
the clutch cone and the drum
even when neutral is selected, forward drive may continue to be
transmitted. If reverse is then selected the epicyclic gear train
to function correctly and the box simply locks up, stalling the
Loss of reverse. Almost
always due to a worn out friction lining on the reverse brake
band. The friction lining on the band is very thin and unless
slippage is detected
very early on and the band adjusted correctly,
it will be beyond saving.
On the one hand, these are
significant faults which render the gearbox unusable, but do bear
in mind that very often the box will have had little or no
attention for very many
years and is likely to have
outlived almost any comparable age unit. All the above are
fixable, but all require a strip down. Once repaired, if
done properly, the box will be good for many years further
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
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
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.
Water ! As these boxes
often live in environments where water accumulates, it is not
unknown for them to become submerged. In the event you find
evidence of water in
the gearbox (milky, emulsified oil -- or just water), it is
important to drain the box as soon as possible and flush it with
clean oil until all traces of water are removed.
Apart from the obvious negative effect of water and rust on all
the machined moving surfaces, the real danger is that if the box
happens to be left in the forward
position the clutch cone may rust to the drum. This can be a
sufficiently strong bond that it is impossible to free it using
the gear lever, necessitating a complete
strip down of the box.
Things to do and not to do:
DO -- Make sure the gearbox and reduction box
contain the appropriate amount of clean oil. SAE80 or SAE90
Gear oil is fine in both boxes.
If you have the original brass plate it may say use engine oil in
the reversing box; this was later changed to the specification
above. Each box has its own dipstick.
Find it and use it !
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
remove whatever is causing the problem. The reverse band has
only a thin lining and will not stand over much abuse.
Leave the gearbox in forward if you are not using the boat for some
time. If there is moisture present in the box, there is a
chance of the clutch cone sticking
to the drum. 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
Make any adjustments to the gearbox selector rollers unless there is
a good reason. Any signs of slippage in forward or reverse should be
quickly, but otherwise ---- if it's not broken, don't fix it.
Use any additives in the reversing gearbox. They may glaze the
linings, causing permanent loss of drive.
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
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 service exchange clutch cones and brake bands
plus bearings, bushes, seals and gaskets. We also stock core unit
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
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.
This page is the property of Listerparts.co.uk. No
reproduction without prior approval and visible credit
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.