The PRM80 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 and 2.5:1 with a common astern ratio of 2.5:1

The heavy duty aluminium gearcase is externally ribbed for strength and heat dissipation.

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 80 Marine Gearbox

Ahead Ratio Pleasure Light Commercial
2.04:1 1.12 0.84 0.74 0.55
2.50:1 0.98 0.73 0.65 0.48
Max. Input Power 47 35 32 24

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.

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 PRM80 according to this classification for any commercial boat is not approved by Newage Transmissions 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.

Newage Transmissions 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.

Oil Cooling

The normal Operating temperature should be in the range 50° to 120° using good quality lubricating oil of the same viscosity as that used in the engine.

Propeller Free Wheeling

The PRM80 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 11.25kg (24.5lb)
Oil capacity 0.56 litres (1 pint)

Flexible Input Coupling for PRM80

Part Number Outside Diameter Mounting Hole Pattern Remarks
in mm No. Diameter Pitch Circle Dia.
in mm in mm
MT8109 8.50 215.9 6 0.344 8.74 7.875 200.0 SAE 6 1/2 in
MT8110 9.50 241.3 8 0.344 8.74 8.750 222.25 SAE 7 1/2 in
MT8111 11.75 298.5 6 0.320 8.13 7.875 200.0  
6 0.320 8.13 9.843 250.0
6 0.320 8.13 10.625 269.9
6 0.320 8.13 10.75 273.1
MT8112 6.12 156.0 5 0.250 6.35 5.593 142.1  
MT8113 5.965 151.5 8 0.256 6.5 5.512 140.0 Hawker Siddeley Marine
MT8114 10.50 266.7 6 0.32 8.10 9.625 244.5 Mitsubishi
MT8115 7.48 190.0 6 0.32 8.10 6.693 170.0 Nanni/Yanmar

Adaptor Flanges For PRM80

Part Number Description Weight
kg. lb.
MT4901S/A SAE5 adaptor 7.5 16.5
MT8083S/A B/W ( Velvet Drive) adaptor 1.4 3.1

Other Accessories For PRM80

Part Number Description Weight
kg. lb.
MT3054 Tailshaft half coupling ( pilot bored) 1.3 2.9
MT3056 Tailshaft flexible coupling 0.7 1.5

installation drawing for the PRM80 in PDF format (80kb)
parts list for the PRM80 in PDF format (244kb)

The PDF files on this website can be read online or printed using the free Adobe® Acrobat® Reader.
If you do not have this software installed on your system, you may download it from Adobe's website.

All information given in this website is correct at the time of publication.   However in the interests of technical progress, design specifications are subject to change without notice.  Accordingly, data given herein should be regarded as a general guide only and does not form part of any contract.  All goods are supplied in accordance with our standard terms and conditions of sale.



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