Transducer Placement? blowback and loss of depth while run

[mdrducks]

I have a 20' lund alaskan, center console, with HDS 5. 2 walker riggers with 4' boom are set to side on stern.

I recently set up an old style cannon speed and temp (SNT) unit. Prior to SNT, I trolled 2.5-2.8 SOG. With SNT at ball at 2.5, I'm now at 3.0-3.2 SOG. At 2.5 at ball, I cannot see ball below 40' on HDS and definitely not probe because of blowback.

When running, I typically loose bottom, and definitely cannot see fish. This past weekend I ran right past fish, 50' in 80' fow. Never saw them.

I'm looking for help on transducer placement or whether I need to extend transducer farther below hull. I think may problem is the angle of boat bottom changes between running and trolling. Any help would be appreciated.

[LongLine]

Angle of transducer makes a big difference on what & where you see down below.

Transducer should sit approx 1/2" below bottom of boat if you want to see anything while running.

Tom B.

(LongLine)

[jekyll]

Ducky:

Sounds like this is your first experience with a probe? Welcome to the world of "confusion". I say that with a smile. The more speed references you have, the more speed choices you have. If you liked running at 2.5 on the GPS, you can now choose to run at 2.5 off the ball. The reality is that your GPS and probe will rarely tell you the same thing. They are not calibrated to a common standard. In fact, probes aren't calibrated to any standard that I'm aware of. So, if you were in absolutely calm water, your speeds would likely be different. What your probe does for you is to give you repeatability at the lures in any direction you troll regardless of how the wind and surface currents are affecting your boat. You need to do some 'sperimenting' to determine the speeds the fish like in reference to your new probe. I can tell you 2.2 is good on my probe but, if our boats were lashed together, your probe might say we were travelling anywhere from 1.8 to 2.5 while I maintained 2.2.

It is not uncommon for a .5 to 1.5 difference between the probe and GPS. If your balls are not showing on the graph when they once were, you are going faster. If you were catching fish at 2.5 to 2.8 on the GPS, I suggest you see what that translates on your probe and start there as the beginning speed point in your experimentation.