The trolling valve enables low propeller speeds to be obtained by the use of an electrically controlled pressure reducing valve in the clutch pressure operating circuit. It also avoids the use of special oils for the gearbox when fitting the trolling valve.

All PRM units except PRM120/150 can be supplied with a factory fitted trolling valve, also a kit containing all necessary parts for operation and control is available for retro-fitting.

The Trolling Valve Kit Comprises:

Trolling valve 
Operating lever 
Connecting electrical cables
Mounting brackets
Pipework
ON/OFF switch and filter

The trolling valve block is of aluminium alloy housing the on/off and pressure reducing solenoid valves. The solenoid valves are hermetically sealed and supplied with DIN 43650 type connectors. (Figure 1 of the circuits and assembly diagrams shows the basic circuit diagram - this is available to download at the bottom of this page). 

When using the trolling valve it will be necessary to change the control valve spool MT4656 with MT1538, This is provided in the kit.

The operating lever is a Morse type NB unit with locking handle. The housing contains the electrical circuits for operating the trolling valve which again are encapsulated to provide a waterproof seal. The lever is complete with:

3 metres 6 core cable to provide the solenoid and interlock switch connection via a multipin plug;

2 metres 2 core cable to provide the 12V or 24V supply;

1 metre cable with spade end connections to the on/off switch.

An ON/OFF switch and two metres of multicore cable with DIN 43650 solenoid and 6 pin plug to connect to lever cable. Additional three metre lengths of cables can be supplied if a longer run is required.

Pipework, brackets and in-line filter are also provided to enable connections to be made to the gearbox

The trolling valve is connected as shown in figure 1 of the circuits and assembly diagrams (available to download at the bottom of this page) and operates as follows:

Depressing the ON/OFF switch causes the hydraulic oil to flow through the pressure reducing valve and by varying the position of the control lever the clutch pressure is increased or decreased with an associated increase or decrease in clutch slip. 

Movement of the control lever only affects clutch pressure when the ON/OFF switch is activated and ensures the unit is failsafe in the event of an electrical failure. 

During trolling the head of the switch is illuminated to give a visual indication of the valve status.

The ON/OFF solenoid is equipped with a manual operation which can move the valve spool in the event of a mechanical failure.

An interlock facility is provided in the form of an electrical connection which can be wired to a microswitch on the fuel rack to switch off the trolling circuit if the engine speed rise above 1200 r.p.m. 

circuit and assembly diagram for the Trolling value in PDF format (36kb)
parts list for the Trolling valve in PDF format (112kb)