Boatbuilders now offer thrusters on boats as small as 20 feet. Thrusters should not be looked upon as crutches; skippers of tugboats and large yachts use them. A thruster is simply another tool in the boater’s box. So, if you’re considering installing one, here are some elements you should look for.
12-Volt vs. 24-Volt
A 24-volt thruster will have less current draw when running and, as a result, may be installed with smaller cables. In general, we recommend 24-volt thrusters be powered via a dedicated bank of two or more batteries.
Hydraulic vs. Electric
Hydraulic thrusters make sense when the vessel is already equipped with an existing hydraulic system. Hydraulic thrusters don’t build up heat or cut out like electric models if you lean on the switch too long. (For an exception, see below.)
Internal vs. External
Water-cooled, electric-powered external thrusters, like the Yacht Thruster models at the top of this page, can be run for long periods of time. They may also require less amperage and, thus, fewer batteries. For these reasons, external thrusters are more DIY-friendly to install — though they are not suited for boats capable of very high speeds.
Biased props (that look like they came off Red October) deliver better thrust than older Kaplan-style propellers. Dual props provide more thrust, though smaller boats will do fine with a single-prop thruster.
Proportional thrusters cost more but allow finer control: The more you push the joystick, the more thrust you apply. Simple on-off thrusters cost less.
This is an available option for most thrusters. It should be an addition to and not take the place of a hard-wired joystick or touch pad. Remote batteries can die at the wrong time, and remotes can mysteriously fall overboard.
Measure to be sure the thruster will fit in the available space. The top of the tunnel should, at a minimum, be 75 percent of its diameter below the waterline, preferably up to 1.5 times the diameter.
An internal shear pin accessible inside the hull is easier to replace than one located in the tunnel. Tunnels will suck in poly bags, mooring lines and other potentially pin-busting materials. Forewarned is forearmed.
A 5 hp bow thruster for a 35-foot cruiser might cost $4,000. Small, 2 kW thrusters are available for about $1,100. Installation will vary, but a yard-installed internal thruster could start at $3,500 and go up from there.