PRM125

Simple mechanical operation, lightweight, compact & rugged

New for 2016, the PRM125 replaces the PRM120.

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, i.e. MORSE MT3 or SL3 which operates the engine throttle in conjunction with the gearlever.

Nominal Power Ratings, PRM 125 Marine Gearbox

Model

Ahead Ratio

Pleasure

Light Commercial

kW

BHP

kW

BHP

125D2

2.04:1

1.31

1.75

0.71

0.95

125D2.5

2.50:1

1.04

1.39

0.71

0.95

125D3

2.94:1

0.86

1.15

0.60

0.80

Max. Input Power

52

70

36

48

Maximum operating speeds : 5000 rev/min

Note: These powers are expressed in BHP and kW per 100 rev/min engine operating speed, and are measured at the engine flywheel. Ratings have been established to ensure the long trouble free life of the gearbox which should not, therefore, be used at powers in excess of those shown.

Oil Cooling

The normal operating temperature should be in the range 50° to 95° 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.

Approximate Weight & Oil Capacity

Approximate dry weight: TBC kg ( TBC lb)
Oil Capacity 0.4 litres: (0.7 pints)


Flexible Input Coupling for PRM125

Part Number

Outside Diameter

Mounting Hole Pattern

Remarks

mm.

in.

No.

Diameter

Pitch Circle Dia.

mm

in

mm

in

MT8109

215.9

8.50

6

8.74

0.344

200.0

7.875

SAE 6 ½ in

MT8110

241.3

9.50

8

8.74

0.344

222.25

8.750

SAE 7 ½ in

MT8111

298.5

11.75

6

8.13

0.320

200.0

7.875

 

6

8.13

0.320

250.0

9.843

6

8.13

0.320

269.9

10.625

6

8.13

0.320

273.1

10.750

MT8112

156.0

6.12

5

6.35

0.250

142.1

5.593

 

MT8113

151.5

5.965

8

6.50

0.256

140.0

5.512

Hawker Siddeley Marine

MT8114

266.7

10.50

6

8.10

0.320

244.5

9.625

Mitsubishi

MT8115

190.0

7.48

6

8.10

0.320

170.0

6.693

Nanni / Yanmar

Adaptor Flanges For PRM125

Part Number

Description

Weight

kg

lb

MT4901S/A

SAE5 adaptor

7.5

16.5

MT4902S/A

SAE4 adaptor

10.1

22.0

MT8083S/A

B/W (Velvet Drive) adaptor

1.4

3.1

Other Accessories For PRM125

Part Number

Description

Weight

kg

lb

MT3054

Tail shaft half coupling (pilot bored)

1.3

2.9

MT3056

Tail shaft flexible coupling

0.7

1.5


Service Classification Definitions - Pleasure

Limited to craft used exclusively for pleasure boating; operation at full engine throttle should not exceed 5% of total time, with balance of usage at 90% of full throttle engine speed, or less. Maximum operation 500 hours per year. The selection of PRM120 according to this classification for any commercial boat is not approved by PRM Newage Ltd.

Service Classification Definitions - Light Commercial

Planing or semi-displacement craft used in pleasure or commercial applications 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.

Important Note

  1. 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.
  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 the transmission components.

PRM Newage Ltd 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.