johan ...a dont know about hummingbird in S.A but in europe there is a waranty
that mean it gets replaced for new if it lets you down , and their waterproof to a couple of metres so if it goes tits up on the water your unit will be ok
like anything you ll use in the salty ...give it a rinse after EVERY use and it will se you alright for a long time
ps ..dont clean window with anything more than soapy water [cold/tepid] not hot
and never spray with wd40
google ACF-50 anti corrosion formula ...and give terminals a wee spray after rinsing that will keep it fine n dandy for many a year
av had a few units from them over the years ....
hope this helps
billy