Starter or House Battery?
Thinking about this I see no reason at all for to run insturments when the engine isn''t running. Ok all kidding aside. ALL engine funtions should be in the circuit with the starter battery. Most of these funtions will be handled by the alternator and therefore have very little impact on the battery. Your house circuits should be limited to the power requirements you want for better living in your cabin and safer living on deck...