My Boat Has 12v and 24v Batteries, Should I Isolate the 24v Service Wiring From the 12v Engine Wiring?

Question:

My name is Daniel and I am writing to  you from the Canary Islands. I’m refitting a 1991 Gib Sea Master 52 sailboat that has a DC 24V installation, except for the engine which is 12V. Should I isolate the 24V service wiring from the 12V engine wiring? Are there any benefits to doing that?  Or otherwise, not having the 24V negative connected to the engine block?  Is that a problem?

I have 2 alternators, the service one is a Balmar isolated, and I’m planning to install a Victron Orion 24VDC-12VDC converter with isolated negatives for charging the engine batteries (2 in  parallel) from the 24V system.

I have seen all your YouTube videos and I believe this question hasn’t been discussed.  Thanks for your videos they are always so helpful and I wait for each to come out!  - Daniel

Answer:

Thanks for reaching out to PYS regarding your Gib Sea Master.  When configuring two different DC system voltages you should still connect all of the negatives to create a common connection between all. Just remember that if you have a shunt installed for measuring the current on your 24V house bank that all other negatives, even from the 12V DC engine battery should be on the load side of the shunt. I agree with your plan to install a DC-DC charger but could consider a non-isolated model based on above.