How much does it cost to install a bow thruster on a boat?
I have a 36ft GRP sailing yacht without a bow thruster, and tight marina berths are becoming hard work. What should I budget for a complete installation, including lifting the boat, cutting the tunnel and upgrading the electrics?
Answer
Budget roughly £5,000 to £9,000 including VAT to fit a conventional tunnel bow thruster to a typical 30 to 40ft GRP boat with straightforward access and suitable electrical provision. Difficult hull work, extensive joinery alterations or a retractable installation can take the total to £10,000 to £20,000 or more.
Check the tunnel will fit
Before comparing thruster prices, have the yard inspect the hull beneath the forward berth, water tanks and internal mouldings. The tunnel must sit sufficiently below the waterline and far enough forward to provide useful turning force.
A shallow forefoot may force the tunnel further aft, reducing its effectiveness, or make a retractable unit the practical option. Follow the selected manufacturer's drawings for tunnel immersion and clearance. There is no universal fitting depth.
As a starting point, many 30 to 40ft cruising boats fall within the 40 to 75kgf thrust range, commonly with tunnels approximately 125 to 185mm in diameter. Displacement, windage and the distance between the thruster and the boat's turning centre matter more than length alone. A tall motor cruiser can need substantially more thrust than a sailing yacht of equal length.
Complete installation costs
Use these UK allowances for budgeting. They include VAT but are not fixed quotations:
- Thruster, tunnel and basic controls: £1,500 to £3,000. Established makes include Sleipner/Side-Power, VETUS and Quick. Check that the quoted package includes the joystick, wiring loom and tunnel.
- Hull cutting, laminating and finishing: £1,500 to £3,000. This covers a straightforward GRP installation, including external fairing and restoring protective coatings.
- Electrical materials and installation: £800 to £1,800. Heavy cable, crimped terminals, fuse, isolator and labour account for a substantial part of the job.
- Lift-out, blocking and relaunch: £400 to £900. Costs vary considerably with location and boat size. Combining the work with a scheduled lift can save money.
- Joinery or tank alterations: allow £300 to £1,500 extra where access is obstructed.
These allowances overlap between yard packages, so compare the complete scope rather than adding every upper figure together. Ask whether antifouling, battery provision, commissioning and VAT are included. Keep a contingency of about 15% for concealed obstructions or additional repairs found during preparation.
Electrical loads and cable runs
A bow thruster drawing nearly 4kW at 12V takes roughly 300 to 350A. Long cable runs cause voltage drop, reducing thrust when you need it.