Have a Garmin 4210 chartplotter. The Unit came with the boat (US boat), but I bought the chart software chip in Perth (Bias Boating) so all charts and information on it is local. I was at Rottnest yesterday and noted the tidal forecast on it for Fremantle and Rottnest waters was completely different than the tidal forecast on seabreeze or BOM. Infact, on further investigation is was definitely incorrect with it showing low tide when it was high tides. Has anyone had this issue with the garmin units? Do you know how to fix? I checked and I had the correct date and time set etc.