Method to operate a marine propulsion system in a trolling mode, control unit and marine propulsion system

Abstract

A method of operating a marine propulsion system (1) in a trolling mode. The marine propulsion system (1) comprises at least one propeller shaft (6) which can be driven by an engine (2), via a pressure operated forward clutch (4), in a forward direction or, via a pressure operated reverse clutch (5), in a reverse direction. A forward pressure is applied to engage the forward clutch (4) to a certain extent and, at the same time, a reverse pressure is applied to engage the reverse clutch (5) to a certain extent. A value of the forward pressure is different from a value of the reverse pressure so that the propeller shaft (6) is caused to rotate in a desired rotational direction. A control unit with mechanism to operate the marine propulsion system according to the method and a marine propulsion system with such a control unit are also disclosed.

1 . A method of operating a marine propulsion system ( 1 ) in a trolling mode, wherein the marine propulsion system ( 1 ) comprises at least one propeller shaft ( 6 ) which can be driven by an engine ( 2 ), via a pressure operated forward clutch ( 4 ), in a forward direction or, via a pressure operated reverse clutch ( 5 ), in a reverse direction, the method comprising:
 applying a forward pressure to engage the forward clutch ( 4 ) to a certain extent and, at the same time, applying a reverse pressure to engage the reverse clutch ( 5 ) to a certain extent, and wherein a value of the forward pressure is different from a value of the reverse pressure, so that the propeller shaft ( 6 ) is caused to rotate in a desired rotational direction.   
     
     
         2 . The method according to  claim 1 , wherein the forward pressure and the reverse pressure are determined to cause slippage in the range of 0% up to 30% at the forward clutch ( 4 ). 
     
     
         3 . The method according to  claim 1 , wherein the forward pressure and the reverse pressure are determined to cause slippage in the range of 70% up to 100% at the forward clutch ( 4 ). 
     
     
         4 . The method according to  claim 1 , wherein the forward pressure and the reverse pressure are determined to cause slippage in the range of 0% up to 30% at the reverse clutch ( 5 ). 
     
     
         5 . The method according to  claim 1 , wherein the forward pressure and the reverse pressure are determined to cause slippage in the range of 70% up to 100% at the reverse clutch ( 5 ). 
     
     
         6 . The method according to  claim 1 , wherein, before applying the forward and the reverse pressure, a prefill pressure is applied to the forward clutch ( 4 ) and to the reverse clutch ( 5 ). 
     
     
         7 . A control unit fora marine propulsion system, wherein the control unit ( 9 ) comprises means to control the marine propulsion system ( 1 ) according to the method according to  claim 1 . 
     
     
         8 . A marine propulsion system, comprising an engine ( 2 ), a transmission ( 8 ) with a pressure operated forward clutch ( 4 ) and a pressure operated reverse clutch ( 5 ), a propeller shaft ( 6 ) which can be driven by the engine ( 2 ), via the transmission ( 8 ), and a control unit ( 9 ) to control the pressure which is applied to each of said clutches ( 4 ,  5 ),
 wherein the control unit ( 9 ) is enabled to control the marine propulsion system ( 1 ) according to the method according to  claim 1 .   
     
     
         9 . The marine propulsion system according to  claim 8 , wherein the forward clutch ( 4 ) comprises a first double acting pressure cylinder and the reverse clutch ( 5 ) comprises a second double acting pressure cylinder.