To use these charts there are two factors (excluding the length of your boat), which you need to determine:

1. The relative size & wind area of your yacht
For a boat of any given length, the area it offers to a direct side wind can vary from one design to another. The underwater shape & total weight can also differ greatly. However, most recreational boats, both motor and sail, will fit into one of three categories:
- Cruising
- Fast cruising
- Super fast cruising

2. The conditions in which you use your boat (thruster force required)
Different people have different uses for their boat. For example, an expedition yacht on a world cruise would have different needs to a picnic boat berthed on a lake. In conclusion, some people would like a more powerful thruster than others. If the size of your boat intersects more than one thruster on the selection chart, the choice of thruster will depend on the situations and conditions in which it will be used.