Pusher Fan Basics
Getting started on the
right foot
By Pete Gregoire
If your boat is anything like mine, then it floats on water. If it doesn’t, then you have bigger problems. Assuming you're dry, the next thought is how to get the boat to move through the water.
For a long time now gas out-boards and electric trolling motors have served as typical sources of propulsion, but anytime there’s something below the waterline it will likely become entangled in vegetation, ground out on the bottom, or bounce off rocks, stumps, etc… That’s why a greater number of boats set up for bowfishing are incorporating pusher fans.
Pusher fans are not really fans, but rather lightweight, low horsepower 2 and 4-stroke engines with horizontal drive shafts that connect to a light aircraft propeller (fan), either directly to the engine, or through the use of a reduction unit to avoid exceeding a propeller’s RPM range.
The engine/fan setup is usually centrally located on the back of the boat, often above and in front of the outboard (if equipped). A shroud encircles the fan for safety reasons and to protect it from coming into contact with things like tree branches. The engine/fan/shroud combination is con- nected to the boat on a pedestal with bearings that allow the
whole unit to rotate a full 360
degrees.
Steering a pusher fan is typically done from the front shooting platform using a variety of different systems which will be discussed a little later.
With this setup a boat is usu-ally only limited by its draft and can get into areas that would destroy a trolling motor/outboard, however your average pusher fan will not allow a boat to run on dry ground like their airboat cousins.
There are a lot of variables to consider when setting up a fan. Performance is typically what comes to mind first. Engine power is a great starting point. Smaller boats should focus on weight and employ smaller engines from 16-25 horsepower.
The output shaft of the engine is also important, as the diameter of the shaft will need to match the hub of the propeller. Beefier
1” to 1 1/16” output shafts are
preferable for strength and longevity. Propellers on these smaller engines can be driven directly off the shaft. This setup is very common and works well for many bowfishermen, although direct drive fans usually need to spin faster to make adequate thrust, thus making more noise and working harder to get the same performance as larger fans with reduction units. Smaller fans, in the 38-42” range, are normally employed with smaller engines.
If stepping up to a larger engine/fan combination is warranted, especially on boats with hull lengths of 18’ or more, then engines from 25-40 HP are often employed with shaft sizes up to 1 7/16”.
Increased horsepower allows the use of longer, or more, fan
(continued on next page)
Photo courtesy of Greg Baneck - Gar-Git-R Charters
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Obscure Adventures Magazine