Been running HDS 9's for two years on Erie. Have been to courses on how to set up these units and bougt videos on this type unit. I have adjusted the transom brackets and tilt of the tranducers probably 8 or so times with no success. Have adjusted the gain and sensitivity as taught at these courses and tapes with little difference. I get a poor reading with the 200 hz setting and NO fish show on the 50 hz, med chirp or high chirp settings at high speed. If you use any interference suppression you get no fish readings. At high speed no fish marks are seen but slow to 3 mph and there they are. You turn up the sensitivity too high and you get some high speed "fish marks" but slow down and there are no fish actually there at low speed. There appears to be some kind of "noise" that is present that competes with fish readings mainly at high speed. Ping is max. Chart speed is at 15 but if you turn it up to max you get false fish readings too . Auto setting may get you a few readings at high speed if there are lots of fish. The power source is hooked to the 12 volt starting battery but readings are not great with the gas motor off and using the 36 volt trolling motors for power. Gas motor on or 36 volt trolling motor has no effect on depth finder readings. Is there anyone out there who has this problem and found a miracle cure after doing all the things you are supposed to do with regard to transducer placement and setting adjutments. Is this an HDS 9 thing? Does any one have a brand of combo depth, down/side finder, and GPS unit that they can reccomend for marking walleyes at high speed on Lake erie. The boat is a 2050 metal starcraft riveted boat and the system was installed by the dealer. I would appreciate any suggestions. I have tried it all. Thanks!