Lowrance X-85

• Based on experiences in Toy Boat 1, it appeared that the stock X-85, with the 192 kHz 20 degree transducer and a transom mount, would be good down to maybe 250' in salt water. We wanted to go deeper, so we contacted Lowrance to see about buying the 50 kHz add-on (Lowrance model SAM-50HPD) to the X-85.
  
  
• Of course, there were no SAM-50HPDs in stock, and because the X-85 was old product, they would not give me a scheduled time to produce a unit. Instead, Lowrance Technical Support recommended adding a second, 8 degree version of the 192 kHz transducer , which would give me a depth range approaching 1000' (due to the narrower beam). We would use a transducer switchbox to change back and forth between the two beam angles.
  
  
• The benefit of using an 8 degree 192 kHz transducer over a 45 degree 50 kHz is that it has better target resolution and is less susceptible to noise. On the other had, it would not have the wide-angle view capabilities of the 50 kHz transducer.
  
  
• In the end, we decided to go with the dual 192 kHz transducers, hooked together with a Lowrance switchbox. We could look at the 8 degree display, or the 20 degree display, but not both simultaneously. The temperature / speed transducer was a separate piece. Everything connected easily together.

Furuno LS-6100

• Putting the LS-6100 together was straightforward, since the LS-6100 was current product and a dual frequency box from the start.
  
  
• We purchased the Furuno 525ST-PWD transducer, which is a plastic speed/temp transom mount dual frequency transducer. In reality, Furuno and others do not make their own transducers, chosing instead to resell transducers from a company called  Airmar. The Furuno 525ST-PWD is really an Airmar P66. Interestingly enough, the P66 was not much smaller than the separate Lowrance pieces combined.

Other thoughts...

When we first got the P66, we thought it was great to have integrated sonar / speed / temperature features in a single transducer. However, after several years of use, we've come to the conclusion that it's a mixed blessing.

We lost the temperature thermistor a while ago, and there was no way to fix it other than by replacing the entire transducer. Along similar lines, the speedometer function on the LS-6100 had always been off, even with a free-spinning paddle wheel and recalibrating it using the LS-6100 setup menus. But we could not replace the speedometer portion of the transducer without replacing the whole thing. Since we had the GPS for speed information, we left it alone. Interestingly enough, when we replaced the transducer to fix the temperature thermistor problem, the new speedometer was no better than the first.

• The Lowrance installation instructions were good, but not quite as complete as the Furuno (see notes below).
  
  
• The Lowrance user manual had more thorough instructions and discussions on how to use the sonar unit than the Furuno. In addition, they also had a great on-line tutorial about sonar technology and how to use it.

Furuno LS-6100

• The Furuno /Airmar manuals contained a few more aids for the do-it-yourselfer that made installation easier. These included transducer mounting templates, wiring diagrams and detailed technical specs (how big is a Passi/Braza, anyway?? ).
  
  
• On the other hand, they did not have very good instructions on how to use the sonar unit, either in terms of configuring the system, or how to interpret the display. Actually, we should say that the instructions are OK if you already know how to use a sonar unit, but if you need help on understanding why or when to change scroll rates, surface clutter, pulse interval, etc., you won't find it in these manuals.

Other thoughts...

One lesson we learned was that you should plan on having to replace the transducer. That means mounting it in such as way as to allow you to take off the transducer and pull the wiring. This is where Cable Clams can really be a plus, since you can get a watertight seal through a bulkhead without permanently sealing the cable in place.

This also means that if you do need to caulk things, the only thing you should be putting in place with 5200 is the transducer mount (assuming the transducer itself can be removed from the mount). Everything else that requires caulking ought to be done with a good removable below-the-waterline caulk like Sikaflex-291. Anti-Bond 2015 will get 5200 off, but it can take quite a bit more effort than working with Sikaflex.

What does this mean to you?

• Furuno, Lowrance and others have their product documentation available on-line. Whether you install the unit yourself or not, take a look at the manual, and familiarize yourself with the installation and setup.
  
  
  • If you are having someone else install the unit, use this information as a guide for assessing the quality of their work. Pay particular attention to the transducer location, and the routing of the transducer wire. Do not be afraid to challenge or question their choices. In some cases, the locations and routings may be a matter of convenience, and NOT the right choice for performance.
    
    
  • If you will be installing the unit yourself,  use the guides to help decide what model and brand to buy.  
    
    
• Beware of add-on modules, especially if the unit is a bit older - check with the manufacturer for confirm part availability first
  
  
• Install the equipment with the idea of making future repairs easier. Specifically, plan on having to replace the transducer and rerun the wiring.