I do all of my own marine electronics installation. It is satisfying but frustrating at times if you don't know everything you should know before starting. Here are some videos to help get you most prepared to tackle your own job.
Wiring for a boat is a unique application with substantial impact on safety and reliability of the boat and people in it. While knowing the basics of electrical wiring and say, automotive electronics is useful, there are major deviations in a boating situation. Boats are exposed to moisture and corrosive salt water. They are also vibrating heavily due to the engines running at full RPM. And there are issues related to corrosion. These necessitate using special material and techniques for the wiring. This is a good but short video on in this area, dealing with bilge pump. Note that while he uses an open flame to heat shrink the tubes, I must prefer a heat gun which is safer and more easily controlled device: