Flange

Getting a thruster flange to seal

A thruster flange is the fitting that joins the thruster tunnel to the hull, and getting the fit right depends on matching it precisely to both the tunnel diameter and the hull thickness at the mounting point, rather than assuming one flange size suits a given thruster model across different boats. Hull curvature at the thruster location also affects how the flange seats, since a flange designed for a flatter section of hull may need packing or a different fitting angle on a more curved section further forward.

Sealing between the flange and the hull is what keeps water out of the tunnel, so this needs proper marine sealant and correctly torqued fixings rather than sealant alone doing the work. If you are replacing a flange on an existing thruster installation, checking the original part number against the current thruster model is worth doing before ordering, since Quick's thruster ranges have used more than one flange design over time.