Thanks, guys – you all gave good advice… Never occurred to me to check the wire gauge since I was getting full voltage right up TO the unit. Nothing like going back to the manual. I’m sure I never paid any attention because this unit repaced a smaller one and I just spliced in the the old, 18 gauge wire… another project!
Thanks!

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It’s a 19 foot Deep-V boat and the Bird is on the bow and the two batteries, in parallel, are in the stern. The wire is 18 gauge, the same or perhaps bigger, than the one supplied, as you state. I never thought of using bigger because that wire on the plug is so small. The voltage reading I took was AT the connector where it goes into the bird.