The evermore is a popular cheap
GPS uni, but anyone of the GPS units that has NMEA
output should work. They also tend to have much better GPS chips than the primitive offerings from Raymarine ( although their new ones are a little better)
Often the new GPS engines will work inside the yacht. Get a cheap
ebay one as a spare. It can wired up ready to go at the flick of switch if the main unit fails.
Another option is handheld GPS (with nmea
output) permantly wired in to 12v and the chartplotter
. Then you have a small very low powered GPS with a screen
for an anchor
watch, or as a backup if the chart plotter fails. (you will still have position, ground speed etc at least)
When the chartplotter
is on it will send a position, but it will function independently if the chartplotter is off.
You should be able to pick up a suitable HH GPS for a bit less than $100.
You will not loose any functionality the the RL80.