The Garmin "Maps" in the Sticky section above will not work with a Lowrance GPS.  However the original "tracks" can be converted to ".gpx" format and then those tracks loaded onto your Lowrance. GPX is the standardized GPS exchange format.
When you download the map I make it will copy the original tracks onto your computer for this very purpose.  They will be in .gdb format and you can you any number of programs to convert them to .gpx.
Word of caution, GPX does not support color or patterns, all tracks will be one color.  Also, you need to check on how many tracks your Lowrance will display at one time, this may not be a problem any more.
A Garmin "Map" is a vector image of many individual tracks.