Your browser version is not officially supported, and you may experience a degraded service. Please upgrade your browser.
Please note: Our central hub is moving, which may cause some delays. Most items are dispatched from our Beccles branch and remain unaffected. You can view Beccles stock availability on each product page. For time-critical orders, or if you’re unsure of stock at Beccles, please contact us.
x
Christmas Opening: On the 20th December we will be carrying out a stock take, no orders will be despatched on this date. To ensure your pre-Christmas order arrives on time, please place it before this date. We will close on Dec 24th - 26th, Dec 31st and Jan 1st 2025. We will open between 9am and 3pm on Dec 27th & Dec 30th.
x

PRM 750D Drop Centre Marine Gearbox (Ahead Ratio 2.9:1)

Part No: PRM-750D3

Full hydraulic operation: offset or down angle output shaft.The PRM750D and PRM750A marine gearboxes are purpose built for use in both pleasure craft and commercial boats; the twin countershaft... Read more

Description

Full hydraulic operation: offset or down angle output shaft.

The PRM750D and PRM750A marine gearboxes are purpose built for use in both pleasure craft and commercial boats; the twin countershaft design provides separate oil-operated multi-disc clutches (which need no adjustment) for ahead and astern drive allowing full rated power to be transmitted continuously in either direction.

To cater for the widest possible variety of boats the PRM750 is offered in two different configurations : with offset output shaft (PRM750D) and 8° down angle output shaft (PRM750A). Reduction ratios available are 1.09:1, 1.459:1, 1.935:1, 2.565:1, 2.904:1 and 3.952:1 (3.952:1 reduction is not available on down-angle gearboxes) all of which can provide either left-hand or right-hand propeller rotation in "ahead", making the gearbox particularly well suited to twin engine installations.

The robust and reliable hydraulic system uses lubricating oil of the same viscosity as that used in the engine, and helps ensure good boat handling by its rapid response to movements of the operating lever.

The operating lever has a positive neutral detent which assists the setting-up of the remote control operating unit whilst for added security, to guard against the unlikely event of hydraulic failure all gearboxes incorporate a mechanical lock-up device so the boat can be brought safely back to port.

The gearcase is constructed of high grade cast iron, internally ribbed for rigidity and strength, and consists of two separate halves to facilitate servicing, the oil pump and hydraulic control valves being externally mounted for easy accessibility.

A special feature of the PRM750D & PRM750A is the direct drive power take-off which is available as an optional extra; this will power a hydraulic pump to SAE J744C type 'B' specification, thus providing an economical and space efficient means of driving on-board machinery.

An electronically operated trolling valve can be fitted, which will allow variable speed of the propeller to zero whilst allowing a maximum engine speed of up to 1200 rpm.

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.

Working Oil Pressure

Minimum - 30.34 bar (440 PSI), Maximum - 33.44 bar (485 PSI). Two tapped holes 1/8" BSP on the top, and M18 x 1.5 on the side of the valve block are provided so that the pressure gauge can be fitted if required.

Oil Cooling

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 two 3/8" 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 bearings which are of adequate capacity for all factory approved ratings.

PRM750 Gearbox spline: 17 teeth 16/32 DP. PRM 750 Gearbox coupling: 6", 6 holes, 4¾" PCD, 3" female register. Oil Capacity: 2.5 litres (4.4 pints).

Specifications
Capacity Description Oil Capacity: 2.5 Litres (4.40 pints) (plus the amount required to fill the cooling circuit)
Material High Grade Cast Iron Gearcase
Weight 72kg (159 lbs) (excluding adaptor, drive coupling and oil cooler)
Brand PRM
Gearbox Manufacturer PRM
Country of Origin United Kingdom
Hydraulic or Mechanical Hydraulic
Shaft Arrangement Drop Centre
Warranty 2 Years
Gearbox Coupling 6", 6 holes, 4-3/4" PCD, 3" female register
Gearbox Spline 17 teeth 16/32 DP
Nominal Power Rating Heavy Commercial 7.02 BHP / 100 RPM
Nominal Power Rating Light Commercial 7.50 BHP / 100 RPM
Nominal Power Rating Pleasure 8.00 BHP / 100 RPM
Ratio Ahead Stern Description 2.904:1
Replaces PRM 401M, 402D
Ask a Question
PRM 750D Drop Centre Marine Gearbox (Ahead Ratio 2.9:1)

£4,136.22

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.

£4,136.22 Incl VAT

 0 in stock

View Trade Prices

Get notified when it's back in stock

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.

Quantity
Check stock in store
Beccles

0 in stock

 Please check with the store before travelling to avoid disappointment

Get offers in your inbox

Sign up for the latest offers, product news, technical advice and more.

By submitting your details you consent to our Privacy Notice.

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.