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PRM1750 FULL HYDRAULIC OPERATION
DROP CENTRE OUTPUT SHAFT
TWO STAGE REDUCTION GEARING
PRM1750 series marine transmissions are the ideal choice for pleasure and commercial craft applications with engines rated at up to 620 hp (463 kW). They are available in both shallow and deep case form - corresponding to reduction ratios ranging from 1.22:1 to 3.0:1 and 3.12:1 to 4.9:1 respectively - and are supplied with integral SAE housings as standard. All PRM1750 series transmissions feature a twin countershaft design compatible with left or right hand propeller rotations - making them equally suitable for both single or twin engine installations. In addition, the PRM1750's two-stage reduction gearing enables maximum input torque of 1750 Nm to be transmitted continuously in either direction at engine speeds of up to 2500 rev/min.
Simple Operation
Operation is by a single lever compatible with proprietary remote control operating systems. The need for special purpose automatic transmission fluid is eliminated by the use of engine oil specification lubricant.
Durable and Reliable
PRM1750 utilises a maintenance-free oil-operated, self-adjusting multi-disc clutches for consistent reliability and in-service performance. The gearcase is manufactured from high grade cast iron and is internally ribbed for extra rigidity and strength. The oil pump, oil filter and hydraulic control valve on all PRM1750 models are mounted externally for easy access and servicing.
Optional equipment
Two optional clutched power take-offs - compatible with SAE classification hydraulic pumps - are available to drive on-board machinery. Further ancillary equipment for PRM1750 gearboxes includes an oil pressure gauge, oil cooler kit and trolling valve.
Nominal Power Ratings - PRM1750 Shallow Case Marine Gearbox
S denotes Shallow Case: manufactured only with integral SAE3 adaptor housings.
Nominal Power Ratings - PRM1750 Deep Case Marine Gearbox
D denotes Deep Case: manufactured only with integral SAE1 or SAE2 adaptor housings. Note: These powers are expressed in BHP and kW per 100 rev/min engine speeds, and are measured at the engine flywheel. Ratings have been established to ensure the long, trouble-free life of the gearbox and should not therefore, be exceeded.
Service Classification Definitions
Pleasure: limited to planing hull pleasure craft with a maximum of 500 hours operating time per year, of which not more than 5% should be at full engine throttle, with the balance of usage at 90% or less of full throttle. The use of PRM marine gearboxes according to this classification in any commercial boat, or in sport-fishing charter boats or long-range pleasure cruisers, is not approved. Light commercial: planing or semi-displacement craft used in pleasure or commercial application may qualify for light commercial rating if annual usage is less than 1500 hours and full throttle operation is limited, with most operating time at partial throttle. Heavy commercial: all displacement and semi-displacement craft used for commercial applications should be classified as heavy commercial duty. In this type of vessel (such as trawlers, purse seiners, lobster and crab boats, tugs, ferries, offshore supply boats etc.) the gearbox is expected to work at full governed engine speed. The power setting of the engine must be known and must be within the permitted heavy commercial rating of the gearbox. Important Note1. It is essential that the engine, transmission model, reduction ratio and propeller size are correctly matched so that the engine can attain its rated speed appropriate to the relevant service classification without labouring. 2. It is also necessary to ensure the torsional compatibility of the complete propulsion system from engine through to propeller, since disregarding this may result in gear noise, particularly at low speed operation and may even result in damage to the engine as well as to transmission components. PRM Marine Limited will provide all possible information and assistance to help find solutions to potential torsional problems, but it is the ultimate responsibility of the person assembling the drive and driven equipment to ensure that they are torsionally compatible.
Operating Pressure
Minimum - 2827kPa (410lb/in²), maximum 3100 kPa (450lb/in²). Two tapped holes, 1 hole 1/8" BSP on the top and 1 hole M18 on the side of the valve block are provided so that a pressure gauge can be fitted if required.
Oil Cooling
The normal operating temperature of the oil should be in the 50ºC - 80ºC range, and should not be permitted to exceed 90ºC. An oil cooler is necessary to ensure that correct operating temperatures are maintained, and two 1/2" BSP connections are provided on the valve block to allow it to be fitted. The size of the cooler required depends on a number of factors including the transmitted horsepower, operating speed, duty cycle, inlet water temperature and ambient temperature.
Propeller Thrust
Both ahead and astern thrust is carried by the output shaft taper roller bearings which are of ample capacity for all factory approved ratings.
Approximate Weight and Oil Capacity
Note: Weight excluding drive coupling and cooler.
Flexible Input Couplings for PRM1750
Other Accessories
Note: When ordering it is necessary to specify the flywheel size. The choice of coupling must be made by the engine manufacturer/boat builder to ensure vibratory torque levels within the driveline are kept to a minimum within the engine operating speed range. This is particularly important as PRM1750 uses two stage gear reduction
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