If you have a Raymarine you have probably gotten the annoying "DSM Connection Lost" alarm. I recently upgraded my electronics and thought that it would go away. It didn't, actually it got worse. So I asked Trevor from Coast Line Marine about it. He checked it out and thought it was one of two things 1. The Battery might be old or 2. It wasn't properly wired to hold the heavy electronics load.
It was no.2 of course. Luckily it was only a couple of hours labor. Basically he ran a heavier Gauge wire capable of handling the load and separated out the fuse panel and put the DSM on its own circuit.
For me it was well worth the cost, haven't gotten the bill yet, but I am sure it wont be bad, he's an honest guy. If you have this problem and want it fixed give Trevor a call. 978-810-5448.