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Equipment

Reverse-Reduction Gearbox

General
Bolinder Marine Diesels are equipped with a sturdy, highly reliable reverse-reduction gearbox. This self-
contained unit is directly flanged to the flywheel housing and is available in two models ; one mechanically
and one hydraulically operated. The same reverse-reduction gearbox is used for both the three and the for
cylinder engines.

Mechanically Operated Reverse-Reduction

Gearbox
Power from the engine flywheel is referred to the reverse-reduction gear through a twin-disc friction clutch.
The gearbox is designed for full power transfer in both ahead and stern drive.
The reverse reduction gear is used both for reversing the direction of propeller shaft rotation and for
reducing the r.p.m. This is done by gearing which, via the drive shaft, transfers the power to the propeller
shaft when either the ahead or the astern clutch plate in the powerful, spring-loaded duplex clutch is
engaged. The clutch is designed to transmit the maximum torque developed by these engines with a wide
margin to spare.

The reduction gear is available with a ratio of either 1.5 to 1 ( more exactly : 1.51 :1 ahead and 1.97:1
astern ) or 3 to 1 ( more exactly : 2.88:1 ahead and 2.53:1 astern ).
The gears are of nickel-chrome steel and case-hardened. The lowest gear works in an oil bath provides
automatic lubrication of all of them. The design permits continuous drive for long periods at a time.
The gear shafts are carried in ball and roller bearings. Shaft seals prevent water from penetrating into and
oil from leaking out of the gearbox.

Fig 22.  Control lever position

Ahead Drive

When the control lever is pushed backwards this movement is transferred via clutch operating mechanism and
link system to the plate which engages forward clutch plate 2 with forward clutch plate 1 of the clutch
compartment. Engine shaft rotation is transferred via gear 17 on astern shaft 9, idler gear 27 and gear 23 to
driven shaft 25, which, together with the propeller shaft rotates in the opposite direction to the previous case.

Adjusting

The powerful duplex clutch with toggle mechanism is spring loaded by the springs in each of the spring
housings. This spring loaded mechanism is designed so that it follows up and compensates wear on the clutch
plates, making all adjustment unnecessary. The mechanism permits a clearance of 0.08 – 0.12 in. 
( 2.1 – 3.2 mm. ) on both sides of a plate when the other clutch is engaged. This clearance increases to a
maximum of ¼ in. ( 6.5 mm. ) in the worn condition. The easiest way to check plate wear and determine when
they need replacing is to check the position on the coupling mechanism shaft end. When the platefacings are
new the distance between the shoulder on the shaft and upper part of the spring housing is approx. 5/32 in.
( 4mm.) ( see fig 24 ) when the clutch is engaged in one direction or the other. When the facings are worn so
much that they need replacing the shoulder on the shaft is about 1/32 in. ( 1 mm. ) above the upper part of the
spring housing. ( see fig 25 ).

Fig 24.

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Fig 25.

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Facing Replacement

If, for some reason or other the clutch is disassembled or worn facings are replaced, the following must be
observed :
The flanges on the spliced plate hubs must be turned towards each other, see 4, fig 23. Otherwise the
plates will not take up the correct positions during operation.



Oil level and recommended oils

The lower part of the reverse reduction gearbox forms an oil sump in which the reduction gears work in a
bath of oil. Oil level in the reverse-reduction gearbox must be maintained between the level marks on the
dipstick, fig 26. Check the level daily and top up with new high-grade oil when necessary. Use oil with the same viscosity as that of the oil in the engine.
The oil capacity of the reverse-reduction gearbox is 5.8 Imp pints ( 3.3 litres )
 

fig 26.

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Oil Changing

Changing the oil in the reverse-reduction gearbox the first time after 100 hours running and then every 6000
hours, but at least once a year. If the engine operates at a higher speed than 1,5000 r.m.p the oil must be
changed every 300 hours. Use oil of the same grade and viscosity as for the engine.

Ball Bearing Grease

The release bearing is lubricated through a nipple ( 13, fig 23 ) which is connected to the bearing by flexible
hose 12. The support bearing in the flywheel and bearing 33 between the ahead and astern shafts in the
reverse and astern shafts in the reverse-reduction gear are lubricated through nipple 21 fig23 at the rear end of
the astern. Shaft. The hexagon plug in end cover 20 must be removed to gain access to this nipple. Lubricate
both these nipples with a high-grade, heat-resistant ball bearing grease every 25 hrs.

DRAINING PUMP

Oil changing in the engine and reverse-reduction gear is facilitated by the provision of a draining pump on the
left-hand side of the flywheel housing. Pipes lead from the pump to the oil sumps of the engine and the
reverse-reduction gearbox.
The cock underneath the crankcase pump can be set in three positions. Handle straight down : Draining pump
connected to oil sump of engine. Handle straight forward : Draining pump connected to oil sump of
reverse-reduction gearbox.
Handle straight back : Cock closed. ( Always set the cock in this position after changing oil )

Fig 29.  Draining pump
 

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COOLANT PUMP

The coolant pump is mounted on the left-hand side of the engine and V-belt driven from the crankshaft.
The pump impeller of oil proof rubber has been splined metal hub and easily removed after taking off the
end of the pump. The working principals of the coolant pump are illustrated below.
 

Fig 30.  Working principals of coolant pump.

1. When the impeller blades leave the pressure plates they straighten out. As they continue to rotate a
vacuum arises behind them and water flows into the pump.
2. Continued rotation of the impeller moves the water from the inlet to the discharge port. Each blade
carriers a given amount of water with it.
3. When the blades regain contact with the pressure plate the y flex and the blades following up force the
water out through the discharge port. Warning. Always check before starting that the bottom valve
( 1. figs 17 and 18 ) is open. If the pump is allowed to run without water the impeller ( of rubber ) may be
So badly damaged by friction that it becomes unserviceable.

BILGE PUMP

The engine is fitted with a bilge pump of the same design as the coolant pump. The pump is driven via a
manually operated friction clutch. The control lever 6, fig 31, is pushed upward to engage the clutch.
When the stop on the clutch lever contacts the stop lug on the pump housing in it’s engaged position, the
clutch must be adjusted.
Adjust as follows : Stop the engine and engage the clutch. Loosen the clamping screw for the drive sleeve
and turn the sleeve a little in a clockwise direction seen from the flywheel end. Do not turn the sleeve too
much each time and make sure that the coupling element does not following the sleeve round. Lock the
sleeve to the coupling element with the clamping screw.
After engaging, check that the clutch arm tensioning device passes the dead point. If it does not, loosen the drive sleeve again, turn it clockwise a little further and relock..
 

Fig 31.  Coolant and bilge pumps.
 

NOTE. When adjusting set the distance between the stop lugs as 3/16 -3/8 in. ( 5-10mm. )
After using the bilge pump it must be disconnected as soon as the boat has been pumped dry. To prevent the
impeller being damaged by friction if the bilge pump continues running when there is no bilge water left to
pump out, the pump is connected to the coolant pump pressure line by pipe 2, fig 31, which continuously
supplies the pump with a little water.

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