# Two sonar transducers



## tsdenney (May 28, 2009)

I currently have an old Datamarine depth finder that is working so I would like keep using it. However, our chartplotter has a sonar option that requires it's own transducer.
The current Datamarine transducer is a thruhull just forward of the keel. Can I place a second transducer (from the chartplotter) in the same vicinity.


----------



## remetau (Jan 27, 2009)

I don't have real experience in this, but I would think that it should work. Are you planning on putting another hole in your boat for it or going with the newer through the hull options? I think I would be against putting another hole into the hull.


----------



## jrd22 (Nov 14, 2000)

You can add another transducer but we had problems with two transducers using the same frequencies interfering with each other. We solved the problem by going to a smart transducer that uses a different freq., I think 233hz? That solved the problem of one or the other of the sounders randomly not showing a reading (usually as we were going into shallower water).


----------



## tsdenney (May 28, 2009)

its seems like it is the only option if I want to use the sonar from the chartplotter. It is either that or remove the old transducer...


----------



## Broomfondle (Apr 9, 2010)

Two tranducers close to each other will almost certainly interact to some extent. This may not be a problem but I guess if it does then you would just have to use one at a time. If you are just keeping the old one as a backup then this might be ok.


----------



## SVCarolena (Oct 5, 2007)

We faced this exact situation on our Pearson 303. The boat has original Datamarine depth and speed gauges and transducers, both of which still work. We added a Lowrance GPS that came with a fish finder. The standard transducer that came with the Lowrance was a transom mount like small fishing boats use. I believe the Datamarine depth transducer is mounted just forward of the keel and to starboard. What we did was to take a plastic bag full of water, place it directly opposite the Datamarine transducer (i.e., same location but to port), ran the wire through the cabin to the head unit, then turned it on and checked to see if we got a signal, which we did. This is commonly called a "shoot through the hull" installation. It usually only works if you have a solid glass hull - cored hulls can interfere with the signal due to air voids. We also checked the Datamarine unit, which worked fine. I believe Datamarine used a different frequency than what is common these days, which is probably why the two units don't interfere with one another. Once we had our location chosen and know everything would work, we then mixed up some epoxy with filler to peanut butter consistency, slathered on the transducer, put some where we were about to install, then worked the transducer to the hull to ensure there was no air between the two. Try the first steps to see if yours will work, then you can decide how you want to mount a unit. Some people use silicone, since it wouldn't need to be ground and chiseled out like epoxy if you ever want to remove the unit. Others install a piece of pipe filled with oil. You can find lots of options with a web search. Of course, it you want another hole in the boat, then you will need to do a traditional install. Even then, you should be able to see if the units will work together by testing with water before you start drilling. Now that we have both units, I almost always use the Lowrance, as it allows me to see contours and compare them to the chart on the split screen.


----------



## Noelex (Jan 23, 2008)

I have 2 depth units mounted only a couple of feet apart. They can be used together without interference, but they are slightly different frequencies.
(Simrad fishfinder 50/200Hz and B&G depth (230 Hz from memory)).
Redundancy is good especially with important information, like depth.


----------



## tsdenney (May 28, 2009)

Thanks all for the helpful response. I didn't believe I would have been the first to face this quandary. Redundancy for all systems is our goal (or whatever it takes to stay afloat).


----------

