To determine the right size of LED light bars for your boat, you should consider the size of your boat, the amount of lighting you need, and the mounting options available. Generally, larger boats require larger light bars, while smaller boats can benefit from smaller light bars. You should also consider the placement of the light bar and whether it will be used for general lighting or for specific tasks, such as fishing or navigation. Consulting with a professional or manufacturer can also help you determine the right size for your needs.