Question for my sailing friends. July 11, 2016

Yesterday I noticed that the line projecting my course was really different between my tablet with Navionics loaded on it, and my Garmin chart plotter. The Navionics course appeared to be correct, showing me about to enter the center of a channel. The Garmin indicated that I was going to run into an island. This is not the first time I have noticed this up here.

On the way into Cove Island I commented to Kerry that a little island we needed to take on the port side was in the wrong place according to the projected course on my Garmin chart. If I had followed the course line indicated I would have hit the island.

So, what is the problem and fix? The Garmin was set for auto magnetic variation increase of  9 degrees west. That's what it was in 2001. I have not been able to find what setting the Navionics has. I could call them today.

Variation has increased 2 minutes each year. So, if I make the variation 9 degrees 30' will that solve my problem? Yesterday after we anchored I switched the Garmin to show true course rather than magnetic. I am not sure if that will help, as we have not moved since then.

I will appreciate any advice and help. How about a pitcher of margaritas to the first person solving my problem! Thanks!