 | 1: The most favorable position for the tunnel is as far forward and as low as possible. The problems are chain lockers, water tanks and shallow draft. Let's use an example of an average 32' sailboat. If the tunnel can be placed forward and low then a good 4 horsepower unit will work. But suppose a built-in water tank is in the most "favorable position". The tunnel would go a couple feet aft and we would probably use a 6 horsepower unit. Lack of leverage arm can be overcome with horsepower. |
 | 2: A good rule of thumb is the top of the tunnel should be at least one diameter below the waterline. The deeper the better. Higher water pressure equals higher efficiency. |
 | 3: The new electric thrusters are surprisingly light for the amount of power they develop. A good example would be an 8 horsepower unit in a 40-foot sailboat. The unit itself weighs 68 pounds. With the addition of a spiral cell battery, overall weight is 118 pounds. Miscellaneous fiberglass and accessories finishes this installation at a weight gain of approximately 135 pounds. A 4 horsepower unit in a smaller vessel that did not require an additional battery could be as low as 60 pounds overall. |
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4: The challenge is fitting bow thrusters into places they were never designed to be. With today's smaller, higher horsepower motors, units can be properly installed without significant influence on the trim of the vessel.
Boats with thrusters generally sustain less cosmetic hull damage, charter companies prefer them and boat brokers report they are easier to sell. |