GPS? Blink Out

[Islandtrader]

Installed my garmin for a trial run (check out build thread to see mods) and the short answer is I like it.

Now the problem (I think I know one solution but seeing if there is something else I can do) the gps is hooked up to the house battery. I have a starting battery on its own. GPS is on and when I start the boat everything is fine no blink out. However when running I went to use the mercruiser power trim and NYC black out on the GPS(trim is on house battery). Had to hard start GPS.

Any ideas? Fixes or suggestions....thanks in advance.