Jupiters Moon

Yes,We’ve gone through all the basics , power , connections etc .

It’s finding their letterbox, not even sure what country the tech teams are from, maybe they are simply IA robots taking the piss. 

That was another reason I dropped Lowrance, went from local technicians to overseas Indian tech help who seemed to know nothing about the units, it could take 45 mins simply spelling your personal details so they can give you a case number. They will also need the serial codes from the box or back of the unit, so tell him to have all that ready or his conversation with the tech guys will normally end until he has it. They will also ask what firmware version he's running and ask him to upgrade to the latest if there is one. They will most likely run him through a soft restart then a hard restart and run the unit on the boat between each of these. Ive been through this on 12in hds mk 3 units only to find firmware updates were the issue and getting the unit back to pre updates was a nightmare. This wasn't just Lowrance but Simrad evo 3 to. Im not alone with these issues, Navico need to lift their act.

Hopefully your friend has checked all electrical contacts and has a fully charged battery. For sounders I like to go direct to the 12v battery and not through any bus bars or fuse panels (still have it fused). I also like to have the battery voltage displayed on the head unit from the menu setup. The slightest bit of corrosion on wires can cause issues with sounders.

Is he the owner of the unit in question??

Most of the time its user error, often just the range is set wrong so that nothing can be seen on the head unit or those functions are turned off in the menu. In saying that I no longer use Lowrance or simrad due to the reliability of them.

What's the transducer? Tripleshot/TotalScan/Active Imaging? And what's the fault? Does the unit not recognise the side/downscan views or does it display them but poorly?
Has he checked all the pins in the cable for corrosion and/or breakages? Any nicks in the cable itself?

My 520 was a little underpowered with a 25 4T on the back. I had a 2.5 aux engine which pushed it along nicely if needed( which it did a couple of times) but the extra weight at the stern bogged it down a bit.
I moved the aux under the cuddy strapping it on top of a seat box and always carried the second fuel tank up front too when full( vent closed)
I didn’t have a stove but these two actions trimmed the boat up nicely and gave me a couple of extra knots.
When o did need the aux, it was light enough to easily manhandle on to its bracket( also kept it in better shape stowed up front.

My 520 was a little underpowered with a 25 4T on the back. I had a 2.5 aux engine which pushed it along nicely if needed( which it did a couple of times) but the extra weight at the stern bogged it down a bit.
I moved the aux under the cuddy strapping it on top of a seat box and always carried the second fuel tank up front too when full( vent closed)
I didn’t have a stove but these two actions trimmed the boat up nicely and gave me a couple of extra knots.
When o did need the aux, it was light enough to easily manhandle on to its bracket( also kept it in better shape stowed up front.

Think you’ve nailed it, bow mounted outboard stick it in reverse. 
 
 

My guess would be a bad earth. Remove and properly clean all the connections.

Check the cheap fixes first, get the multimeter out, check supply voltages, earths etc

Here's where the relay is located on an '08 MY DF100. It's unlikely to be any different for a 2012 MY.

Fingers crossed it's a simple fix for you but if not then the pump would be my next guess too.

Blimey, if I wanted to be nagged, I’d stay at home with the Missus😂😂😂

Blimey, if I wanted to be nagged, I’d stay at home with the Missus😂😂😂

Blimey, if I wanted to be nagged, I’d stay at home with the Missus😂😂😂

🤣🤣 "And mind you take your shoes off before coming in here, you'll leave a trail of muck and I've just hoovered!"

Blimey, if I wanted to be nagged, I’d stay at home with the Missus😂😂😂