Depth issues (read-out not responding to setting changes)

[Ranger]

Or maybe the math is just kicking my...

TZT16, with 525STID-MSD. Keel daft (actually prop draft) is 4.6". The transducer is 3.6' below the waterline.

Actual depth in our slip just this minute is 5.3' -- according to the other depth finder, which I've checked against an actual bottom measurement using a boat hook.

FF read-out is hovering around -2.4'... minus 2.4'... seemingly no matter what I do, no matter where I set the "transducer draft" number. Currently set to 0.0. Have tried 1.1' (near enough to transducer draft, over prop depth), 3.6' (depth below waterline), several other numbers... nothing seems to change. I'd expect a) a positive number, and b) a value approx. .9'.

I've done a factory reset:
-- FF setup -- set hardware to factory default
-- TD setup -- reset default settings
-- auto-cruising is ON
-- auto range is ON
-- bottom search mode is OFF (earlier I was having some' "hunting" issues"
-- I've reviewed all the potentially related threads here

Soft mud bottom, here in the slip.

Guidance?

-Chris

 

[FishTech]

A very soft mud could cause it to read slightly deeper than actual.
The proper entry method for transducer and keel drafts is measured from the surface.
There is the offset entry in the Initial Setup menu for the depth digit.
There is another in the Fish Finder menu for the image.

 

[Ranger]

I finally got to a point where read-out results are credible again. Some combination of starting point (under keel or sea water level), offset, vessel draft... maybe whether I made the change with my left hand or my right...

I tried so many changes, though, that I'm not entirely sure which did what.

And then the "hunting" problem persists. Sometimes depth read-out while underway is credible and stable, sometimes it advances to a few thousand feet, then a few hundred, then three dashes, finally (eventually) lands on credible and stable again.

-Chris

 

[Ranger]

The unit still "hunts" to varying degrees, sometimes while underway, sometimes while in the slip.

We just returned to the slip yesterday, and find we have -2.5' of water displayed in the data box (again). That's MINUS 2.5' of water. Although on the data source page, at approx the same time, depth was approx PLUS 2.3'.

I think something's hosed up...

-Chris

 

[Johnny Electron]

Sounds like the installer has put in one of the depth offsets with the wrong value.

 

[Ranger]

I eventually messed with offsets myself, so pretty sure I have those correct. (Not on board just now, so can't look up...)

But the problem seems to be about inconsistency, somewhere. Underway and in the slip, sometimes the finder hunts all over the place, sometimes landing on a reasonable value, sometimes not so much. And the whole idea of MINUS depth readings is even more confusing, especially when at other times the finder reads OK. This with no changes to offsets or other settings in between occurrences...

-Chris

 

[Johnny Electron]

Hunting is normally related to turbulence. To provide good depth a sounder needs to see the bottom to provide the distance to it. Maybe you can provide some screenshots at different depths that we can look at?

 

[Ranger]

Maybe you can provide some screenshots at different depths that we can look at?

I'll see what I can do. Happens also while were docked in the slip, though, so I suspect turbulence isn't (always?) the issue in that case...

OTOH, I could see turbulence being a cause when we're on plane, especially if the transducer might be mounted too far forward? It's the same "forward-ness" as the other two transducers, though, an orphaned original (which I guess maybe read OK when it was alive), and the DST200 (Airmar DST800) that somebody installed when they replaced an original plotter of some sort with a Garmin 7612xsv.

The TZT16F is back to displaying credible depths -- today -- the MINUS depths have been replaced by likely values -- and I've made no changes in settings.

-Chris