If you really want to silicone the transducer to the hull, all (most?) depth sounders provide the means to adjust the display reading to account for the difference between the transducer's location and the true depth of the keel. If the 1.7 foot error reading you get with silicone is consistent at all depths, simply factor it into your setting adjustment and forget about it - until you have to re-set for some reason. Cheers, Garrett

e16@telus.net writes: > all (most?) >depth sounders provide the means to adjust the display reading Mine doesn't. It's almost as old as I am. You might have seen one like it during an earlier incarnation (little red lights running around in a circle). It's easy to read, quite accurate and dependable except for the differential. So I have to exercise the old gray matter and add 1.7 to the reading I get from the instrument. I can handle that! George of Scaramouche