The best replacement for navionics is lakemaster.

The best alternatives to navionics are rated as following:
★★★★★  lakemaster
★★★★  insight
★★★  inavx
★★  bluechart
★★  cmap
★  nauticpath
★  fishing hot spots
★  c-map
★  isailor
★  garmin charts
★  c map
★  hot spots
★  nautic insight
★  inavx ipad
  jeppesen
  lake insight
  imray
  flytomap
  blue charts

Your alternative for navionics is not listed? Suggest!
Speaking about navionics, one probably shouldn't forget about mobile navionics.

Other search terms related to navionics and their ratings are:
★★★★★ mobile navionics
You have in mind a companion for navionics and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of navionics in all years. Click on graph for more.
navionics
lakemaster
insight