The kit ensures that the propeller is submerged well below the waterline so that the stern thruster functions correctly. For 150 mm tunnel diameter. For the stern thruster to function correctly it is important that the propeller is submerged well below the waterline. If this is not the case the propeller may suck air into the tunnel with a considerable loss of thrust power as a consequence.However on some boats this is not really feasible because the draft at the stern is too shallow and because the thruster assembly should never protrude beneath the bottom of the boat.In order to ensure both tunnel openings are sufficiently below the waterline VETUS has developed an extension kit for stern thrusters. This kit consists of two shells made of GRP together with all the necessary stainless steel fastenings.The kit can be easily retrofitted to existing installations. It should be used if the transom is fitted with other equipment which may prevent unhindered water flow through the tunnel.It is also ideal for so-called “house boats” which in general have a very shallow draft both at the bow and at the stern.