Working on a boat recently that had a voltage drop issue. After some fault tracing I found the issue to be that the house feed and house ground to be too small gauge of wire to handle everything that had been added to the boat in its 10 years of life. Also figure in that the manufacturer used the smallest gauge wire specified by the ABYC. Combine those two issues and electronics start acting funny or not even working. I have seen helms go dark at the use of a bow thruster.
To prevent this problem don't go with the minimum size wire. Seems pretty obvious right? Try to think ahead a bit. Lets say you are putting a new T-top on your center console boat. You install an MFD and Durabrite lights, but hold off on the radar for now. You know you will want to install a radar in a couple more years along with some more Durabrights. Size your wire accordingly and give yourself some margin for corrosion and other things that would add resistance. Remember the more efficiently your electrical system is the longer battery life and longevity you will have. Bow thrusters (and stern thrusters) are big load on an electrical system that I see cause problems. On one boat I worked on in the past the bow thruster was fed from the house bank some 12 feet away with 2/0 AWG cable which at the time of launch may have been ok. Some years down the road it started dropping the electronics every time you used the bow thruster. In my opinion large loads like thrusters or electric pot haulers should have there own designated battery located close as possible to the load and a battery switch installed between the load and battery. To charge the battery I like to use an ACR or an Echo charger coming off of the house bank. This prevent any voltage drop from interrupting the electronics.
I know what many of you are thinking. Larger sized wire, ACR's, battery switches and batteries cost a lot of money. Yes but so doesn't a tech like myself running new wires through your boat, or taking a forward bunk apart to install a battery and etc. Do yourself a favor and plan ahead when wiring or rewiring a boat.
List of components mentioned: I like to use West Marine (https://www.westmarine.com/)for majority of my electrical and other marine supply need. They are very supportive of small business, prompt in responding to questions, and have stores throughout the country.
ACR (automatic charging relay) https://www.westmarine.com/search?q=ACR&prefn1=manufacturerName&prefv1=BLUE%20SEA%20SYSTEMS Pick the one that bes suits your purpose.
Feel free to contact me for any questions.