Hey Jose!
We actually have a document talking about installing charts on your MFD12. Here is the link -
https://www.furunousa.com/-/media/s...chart_and_data_full_installation_guide_v3.pdf
It's a super helpful document and you can still get new charts for that system! If you go to furunousa.com then at the top of the page select DISCOVER PRODUCTS> BROWSE ALL PRODUCTS> scroll down and select CHARTS.
That is a list of charts which you can sort through to find the one you want. Then you would call your local dealer, give them your MFD12 system ID, the chart number you are wanting to purchase, and they will get you the download with the unlock code!