Bloody useful (when you first get it) was able to find the sweet spot for the outboard and the hull and save fuel. I do use it as a fuel guage and find it to be quite accurate. For that money I would grab it. Can sell for more than that if you dont like it

 Wont be  buying another....

I got mine from Boat Bits in Takapuna, but it was just a one-off with damaged packaging on the specials table, so I'm not sure if you'll be able to get the same price again.  The instrument has been going well though, pretty useful bit of kit.

 

Navman fuel computers haven't been made for a few years now.  Parts are like rocking horse **** so if you find them best to buy them.  From what I understand their system was unique meaning that their parts were not interchangeable with any other brands fuel flow sensors etc).  They do use NMEA2000 though so can connect into most other brand plotters etc.

 

A common problem with the 100mm square head units is failure of the ribbon between the mother board and the lcd screen.  There is/was an electronics repair company called Equal Electronics that has a couple of the former Navman techs who can repair this. 

 

I have a diesel 3100 unit and its good for all the reasons listed above, particularly finding most economical cruise and trim etc.  Can't say its that accurate, about 10-15% out at cruising revs and 25-30% wrong at trolling revs. It's on the right side though so always more gas in the tank than the unit shows which is a good thing.  Have a BEP electronic fuel gauge with ultrasonic sender and these are the ducks nuts for showing fuel remaining.  Accurate almost to the litre in my 350l/1.6m long x300mm deep tank.