I am about to start a major rewire on the boat. Which brings up some
ideas and questions.

Idea/question 1. I have seen those expensive power filters for boating
electronics. Why can't I just build a dedicated power buss and drop
some capacitors across the power feeds to each instrument? As in going
back to when we had to build our own power supplies for computer floppy
drives.

The electronics I will be trying to protect are ...
VHF
GPS/Chartplotter combo
Scanning sonar (Interphase)
Radar
SSB
Autopilot

And I may put a second radar and/or scanning sonar at the upper helm.

Question 2. When and where should I use twisted pairs and why not just
twist everything, everywhere?

Earl Haase