SIP SM13010 GRP TUNNEL, 300 X 1000 X 10MM, SE250/300

GRP tunnels are available in several lengths for each thruster model. They are purpose built for Side-Power thrusters and provide the ultimate in strength, accuracy and osmosis protection to ensure an easy and safe thruster installation.
The wall thickness is adapted to each thruster's power and typical vessel size. Unlike most other thruster tubes, Side-Power thruster tubes are not just spun from single threads but, in addition, contain several full layers of strong fiberglass woven roving.

Tunnel Selection –
The diameter of the tunnel will be determined by the model of bow thruster and its propeller diameter. Tunnel diameter refers to the internal diameter of the tube.

The optimal tunnel length is between 2 and 4 times the tunnel diameter – measuring the shortest dimension of the installed tunnel (almost always along the lower side of the tunnel).

Tunnels which are too short allow the propeller to cavitate – which decreases performance and makes a lot of noise.
Tunnels which are too long have higher internal friction which reduces thrust. This becomes very noticable when the tunnel length exceeds 6 or 7 times the diameter of the tunnel.

Tunnel Installation Tips -
The tunnel should be placed as deep as possible so the propeller does not draw air from the surface – which will completely eliminate the thrust. Additionally, the deeper the prop, the greater the water pressure on the blades – which maximizes the efficiency of the propeller.

Generally the top of the tunnel should be a minimum of 1/2 x the tunnel diameter below the waterline. This is an absolute minimum and Side-Power recommends that it be at least 3/4 x tunnel diameter below the waterline. An even better distance would be 1 x tunnel diameter below the waterline.
Once you get the top of the tunnel 1 foot (30-35 cm) below the surface, other factors should be considered more important – for example, moving the thruster further forward to get better boat turning leverage.

We highly recommend that you refer to the excellent "Thruster Location and Tunnel Installation Guide" linked in the Manufacturer's Resource section.