I received a "free" lakemaster map from Humminbird after purchasing one of their fishfinders.  I need to download it onto an SD card.  SOMEWHERE in the fray, but I'm now unsure where, I think I read it had to be a 32 GB SD card and ONLY a 32 GB SD card.  Does anyone know if this is true?

True? Not sure, but I used a 32gb to do my updates just to be safe.

It needs to be an SDHC card, which can't be above 32GB in size.  Anything from 4GB-32GB should be fine.  

 

The technicals behind it is the Hummingbird requires a FAT32 file system to read off of.  SDHC cards, typically the SD cards in sizes from 4-32GB, are FAT32.  Cards below 4GB are typically regular SD cards, which are FAT16 file systems.  I don't know if the Hummingbird will work with them.  Usually, this stuff is backwards compatible, but not always.  Cards above 32GB are SDXC cards.  They use an exFAT file system, and the Hummingbird can't read that.    

 

So my guess is anything 32GB or below would probably be fine.  Though I'm less confident in cards below 4GB.  

Any SD card will work as long as you format it to FAT32. It’s a simple and quick process to do so.

32 GB max.