The PRM150 marine gearbox is purpose built for use with both pleasure craft and commercial boats; its twin countershaft design provides separate oil-operated multi-disc clutches (which need no adjustment) for ahead or astern drive allowing full rated power to be transmitted continuously in either direction.

The reduction ratio is 2.09 and is suitable for both left-hand or right-hand propeller rotation in "ahead", making PRM150 particularly well suited to twin engine installations.

The heavy duty aluminium alloy gearcase is internally ribbed for rigidity and strength and consists of two separate halves to facilitate servicing.

The hydraulic operating system functions on normal multigrade engine oil, avoiding the need to use automatic transmission fluid, and ensures rapid response to movements of the operating lever for good boat handling. The operating lever has a positive neutral detent and is suitable for use with proprietary single lever remote control operating systems.

Robust and reliable, the hydraulic system is nevertheless provided with a mechanical lock up device for added security, so that in the unlikely event of a hydraulic failure the boat can be brought safely back to port. Access to this device is via the detachable manifold on the rear of the gearcase which also houses the hydraulic control valve.

Note: These powers have been 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.

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 PRM150 according to this classification for any commercial boat is not approved by PRM Marine Ltd.

PRM Marine Ltd recommends that when considering the PRM150 in boats of whatever hull form used in commercial applications, and semi-displacement hull boats for pleasure applications, these boats should be classed as commercial duty and the gearbox selected accordingly.

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 Marine 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.

Minimum - 2500 kPa (370 lb./in²), Maximum - 2850 kPa (420 LB/in²). A tapped hole ¹/₈" BSP is provided in the rear manifold so that a pressure gauge can be fitted if required.

The normal operating temperature of the oil should be in the 50°C - 80°C range and should not be permitted to exceed 90°C. An oil cooler is necessary to ensure that correct operating temperatures are maintained, and the gearbox is provided with two ¼" BSP connectors to allow it to be fitted. The size of the cooler depends on a number of factors including the transmission horsepower, operating speed, duty cycle, inlet water temperature and ambient temperature.

The PRM150 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, e.g. in multi-engine installations or when sailing.

installation drawing for the PRM150 in PDF format (46kb)

Free delivery to England & Wales only.A Carriage charge applies to items shipped to scottish highlands and any offshore islands. Please contact us with your postcode before purchasing to check on carriage charge.