Doc Sonar,
I just purchased a Ranger 620VS and have a Lowrance HDS 10 at the console and Lowrance HDS 5 on the bow. I am having problems with loosing bottom at speed over 10 mph. I took it back to the boat dealer and they put an external transducer mounted back by the drain plug to use instead of the thru-hull transducer. Well, my sonar unit I still have the same problem of not being able to read bottom when moving. I called the dealer and they said to turn up the ping speed as high as it goes, but that didn’t work so I called Lowrance and they told me the transducer was not mounted deep enough. Before this boat I had the same issue. Do you have any advice?
Thanks, S.B.

S.B,
You should be able to get high speed reading with either the transom mount or a glassed in mount. It sounds like you need a professional who is experienced at mounting transducers look at your transom transducer to see if it is mounted correctly. You could send me photos of your mounting, but it is difficult to get good photos to interpret.  On the other hand the glassed-in  transducers needs to be installed without air pockets for really good high speed readings. A skimmer transducer is similar to a clam shell and the line that separates them should be installed below the hull. The line should be parallel to the hull or the back end of the skimmer transducer slightly lower than the front.

I get a new Crestliner every year and mount two transducers on the transom and they always perform great up to 56 mph. In general, transducers rarely fail and they will not perform well at high speed. I get reading at 55 mph with a ping speed of 15 so I don’t think increasing the ping speed will help.

Be persistent and check the Lowrance HDS manual for instructions and pictures on mounting your transducer. Remember, if the transducer is mounted correctly you will get good high speed readings.

Thanks
Doc Sonar

For more information on using your sonar, GPS, Lowrance Structure Scan, or to get instructional DVDs by Doctor Bruce Samson aka Doctor Sonar go to www.hightechfishing.com