Description
Simple mechanical operation, lightweight, compact & rugged.
The PRM125 gearbox is designed for use in pleasure craft where a simple lightweight transmission is required.
The cone clutches for both ahead and astern are mechanically operated and require no adjustment.
The gearbox is purpose built to operate with standard rotation engines i.e. providing a clockwise rotation of the gearbox input shaft when viewed on input. In forward drive the output shaft rotates opposite to input shaft therefore requiring a right hand propeller.
The reduction ratios offered are 2.04:1, 2.5:1 and 2.94:1 with a common astern ratio of 2.5:1
The heavy duty aluminium gearcase is externally ribbed for strength and heat dissipation and therefore requires no oil cooler.
Direction actuation is by a lever with positive detent positions for ahead, neutral and astern. It is suitable for use with proprietary remote control operating systems which must be of the single lever dual action type.
It is essential for the engine, transmission model, reduction ratio and propeller size to be correctly matched so that the engine can attain its rated speed appropriate to the relevant service classification without labouring.
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 the transmission components.
Oil Cooling
The normal operating temperature should be in the range 50°C to 95°C using a good quality Automatic Transmission Fluid.
Propeller Free Wheeling
The PRM125 output shaft can be rotated continuously with the gearbox in neutral. It is therefore not necessary to fit a propshaft brake when running with the engine shut down, for example when sailing.
PRM120 Gearbox spline: 10 teeth B10 x 23 x 29mm DIN 5464. PRM 120 Gearbox coupling: 4″, 4 holes, 3¼” PCD, 2½” female register. Oil Capacity: 0.4 litres (0.7 pints).
