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 TM 55-1905-219-14-4
3-8.
MARINE GEAR - MAINTENANCE INSTRUCTIONS.
a.
General.
(1) The Model MG-514 Marine Gear is a marine reverse and reduction gear. The marine gear may be
operated continuously in either the forward or reverse position. Identical ratios in forward and reverse permit the type of
installation known as "twinning"; that is, mounting two gears on right-hand rotation engines and running one gear in
forward and the other gear in reverse to obtain opposite rotation of the propellers.
(2) This marine gear is completely hydraulic in all phases - all bearings are oil lubricated, both clutches are
engaged by high pressure oil, and both clutches are cooled and lubricated by low pressure oil. Refer to paragraph 3-8.1
for oil base maintenance instructions.
(3) A mechanical lock-up, or come-home, feature is provided for clutch engagement in the event
emergency operations are necessary.
(4) The forward clutch shaft and the reverse driving gear always rotate in engine direction. The reverse
clutch shaft and the reverse driven gear always rotate in anti-engine direction. When the forward clutch is engaged, the
output shaft gear will rotate in an anti-engine direction due to the gear meshing with the forward pinion. When the reverse
clutch is engaged, the output shaft gear will rotate in anti-engine direction due to the gear meshing with the reverse
pinion.
b. Hydraulic System.
NOTE
All pressures given in this section are under the following conditions only: An engine speed of 1800 rpm with a
recommended oil in the gear sump and a sump or heat exchanger inlet temperature of 180 degrees F (82 ).
C
Pressure readings taken under other conditions will vary.
(1) Description. The hydraulic system in the Model MG-514Marine Gear distributes both high and low
pressure oil for clutch engagement, cooling, and lubrication functions. The sump, which is located in the bottom of the
main housing, contains an adequate amount of oil for all functions of the system. The oil pump assembly pressurizes the
oil for both high and low pressure requirements. The selector valve assembly is both a pressure regulator and distributor
for the hydraulic system: The manifold is not only a protective cover for the clutches, but also a distribution component
since it contains passageways for high and low pressure oil distribution.
3-286
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