The Lister LH500 (or LH5 as it appears in some
manuals) Marine Gearbox is the standard fitment for the HRS6
(Turbocharged) and optional on
the normally aspirated four and six cylinder HR and
It is mounted at the flywheel end of the engine and is
a self contained unit with its own oil supply and final output gearing
as an integral part of the whole assembly.
The LH500 was available as a direct drive unit or with
a reduction ratio of 2:1 or 3:1.
page is the property of Listerparts.co.uk. No reproduction without
prior approval and visible credit
Lister LH500 -- How it works:
As with all Lister's own marine gearboxes, a
drum assembly fitted with an epicyclic gear train is utilised to allow
for the selection of reverse.
Forward is achieved using a dedicated clutch housing
and multi plate clutch assembly.
LH500 utilises oil pressure, generated by an internal oil pump, to
achieve forward and reverse. With the engine off, neutral is the
default position. The oil pump
driven by an internal drive gear, which turns whenever the engine is
running. A piston concentric with the mainshaft pushes the
multi disc clutch pack into engagement
forward drive is transmitted by means of externally toothed
clutch plates in permanent engagement with the clutch housing (which
is always rotating when the engine is running)
drive to internally toothed plates which are in permanent engagement
with the mainshaft. When the oi pressure is removed from the
piston, a spring pack withdraws
pressure plate, allowing the clutch plates to freewheel relative to
each other and no drive is transmitted.
by an internal extension gear, the reversing brake drum also spins
whenever the engine is running. With neutral or forward selected, it
freewheels on the mainshaft.
reverse is selected, a dedicated piston actuates the drum brake
band, stopping the drum turning. The epicyclic gear train then comes
into play, acting on a gear splined to the mainshaft,
reverse rotation of the shaft.
is a pinion gear on the outer end of the mainshaft, forming one half
of the output gear set., the shaft terminating in a roller bearing
housed in the rear cover. The main output
sits on a dedicated output shaft / flange assembly, carried on two
taper roller bearings, with provision to adjust the bearing preload.
selection is by means of a valve assembly attached to the top of the
gearbox housing. In either air or water cooled engine
applications, the gearbox oil is taken through an
cooler. The oil is also filtered by means of a readily accessible
spin on filter.
the event of the loss of hydraulic pressure, there is provision to
lock the gearbox mechanically in forward drive.
What are the common
have seen so few of these boxes and receive so few requests for
parts or information that we are not sure whether a.) they just
don't break, or b.) they produced very few of them.
would welcome any input that may be helpful.
Things to do and not to do:
to the oil and filter change intervals.
the oil level on the dipstick just as you do for the engine.
If the gearbox is losing oil, the cause should be investigated and
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
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.
If drive is lost, be sure to check for any failure
in the external oil cooling circuit,leading to loss of oil.
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.
Make any adjustments to the gearbox reverse brake
band unless there is a good reason. Any signs of slippage in reverse
should be investigated quickly, but otherwise ---- if it's not
broken, don't fix it.
Use any additives in the gearbox oil. Additives may
glaze the linings, causing permanent loss of drive.
Use more than the minimum amount of power necessary
if the gearbox is in the emergency locked ahead position. The fact
the hydraulics have ceased to give you drive
indicate a significant oil issue and general lubrication may be
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. New,
old stock availability is poor. If you have a problem with your box,
please call. Most things
we are able to sort out, but be aware that items
made to order are likely to be expensive.
Periodically, we have core units for rebuild and may
then be able to offer a complete gearbox on an exchange basis.
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 !
These gearboxes are a scarce item (at least in the
UK). If you run one and someone offers you new parts for it,
or a complete
spare, bite their hand off !
If you really don't want them, we are always
interested for stock.