Furuno, all the way...
Even the 600 is a good unit

 Getting a bit long in the tooth, now. You probably will find, that, if it fails, it will be throw away. I seem to recall they were among the first of the colour LCD sounders, previous colour sounders had been CRT. First out in the late 90's maybe? I was eying one off as a second sounder for the crayboat at the time, for casual flybridge use. I used one for five years on my last 6m tinny, and had no complaints.  Paired with a P66(?) transducer, I saw good bottom readings down to 200m, although I never fished that deep.  I would rate it as a "better" sounder than the Hook-9 ( similar to Elite-9?), but without the bells and whistles. No track back, no ability to put a cursor back over the lump you realise you just trolled over in the middle of nowhere without turning around, as you can with the Lowrance, stuff like that. Either sounder will give you a good bottom picture with the right transducer. 

If you can pick up the -600 cheap enough, I'd be tempted to use it, and just use the Lowrance as a plotter. If the Furuno fails, well, you just start using the Lowrance. I have an Elite-7 combo, and, IMO, it has one really irritating feature--the menus are context sensitive. Change the page, and the menu changes. If you want to make sounder adjustments, you must first select the sounder page. Change the plotter zoom? You need to select the plotter page. Much easier with the touch screen models, such as the HDS and the Elite Ti--the non-touch screens need a LOT of button pushing. Doesn't sound like much, but it is if you are really working your equipment, as I tend to. My solution is to buy a HDS or Elite Ti down the track a bit for a pure sounder, and just use the Elite 7 as a plotter.  

 I can get the fcv600 for $150 wjth transducer and manual book. Pretty old I think early 00's. 

Didnt even think of the track back feature... might go with the Lowrance as a combo for now.

 For $150 if it works youd be a mug not to.
I had one, now a 620.Also have a Lowrance 9.
As a sounder the Lowrance is a major pain to adjust.

The Furuno will teach you things and is very user freindly

 Righto you guys have twisted my arm. Ill go buy the Furuno tomorrow on my lunch break. Will get a Lowrance HDS 7 from BCF as plotter.

 As Rob H  says, Lowrance is a major PITA to make adjustments with on the sounder side--some of it down to the combo issues I mentioned earlier, some of it just down to the need to push a lot of buttons to make simple adjustemnts. But the touch screen of the HDS makes that a lot easier.  The Furuno? You really are just adjusting Gain, Range and Shift, and they all have their own controls. Good bottom lock,  too. Here's something I found very useful--use a shallow range, say, 5 fathoms ( 10 metres) and then just keep your bottom echo in sight with the use of Shift. Acts as a zoom if you are really focussing on demersals or bottom type. To do the same thing on My Elite, you need to create a custom range. PITA.

 Cheers for the tip. Getting new battery and the Furuno installed tomorrow. Saves me doing it on the weekend and eating up valuable fishing time.