Ray ST60 Depth issue

[Tutti]

Hello,

Anybody have any experience with ST60 depthsounder?We have ST60 installed (wind, speed, depth) a year now and found depth to be very unreliable when in water shallower then 3 meters (10ft?), especially in tidal waters.
We've had readings of less then 1 mtr (3ft?) but still afloat with 1,85 mtrs draft.
This also occurs when approaching shallows that rise rapid p.e. when moving between sandbanks (we do keep clear of those).
Installation has been done to the book, even position of transducer.I've checked for loose caulking around transducer (on land at the moment) so cavitation is excluded.

Thanks in advance,

Marc
S/V Tutti, (Nantucket33 by Alan Guerny)

[night0wl]

Have you set your keel offset?

Here is what you have to remember, the transducer is at the bottom of the hull....not at the waterline. So, typically, you have to program in an offset into the instruments to accurately reflect the depth under the waterline...otherwise your depth will be under-represented and you can have freak-out momemnts. The only way I was able to do this was to measure the distance from my hull where the transducer was to the water stain where my waterline was, then put that value into the instruments. I've also used a handheld depth sounder at surface then programmed in an offset using that vs what my instruments were reading.

Of course check all the connections and the transducer to make sure they're working...but my bet is that your offset is not established.

[Tutti]

Hi Night0wl,

Thanks for the reply.
Yes, keeloffset is set, but is non-relevant to what is being measured. Only thing you would do is give+or- to end result.
What i mean is, at one point system showed less than 1 meter when keel was not even close to bottom, if it were for the ST60 we would have been burried for 85 cm's, i guess depth was between 2 and 2,5 meters.
Same happend between 2 sandbanks, about 3 meters deep, but system
shows 1 to 1,20 meters. Heartrate was way up first time.

Marc

S/V Tutti ( Nantucket 33 by Alan Guerny )

[MarkSF]

Originally Posted by Tutti

Hi Night0wl,

Thanks for the reply.
Yes, keeloffset is set, but is non-relevant to what is being measured. Only thing you would do is give+or- to end result.
What i mean is, at one point system showed less than 1 meter when keel was not even close to bottom, if it were for the ST60 we would have been burried for 85 cm's, i guess depth was between 2 and 2,5 meters.
Same happend between 2 sandbanks, about 3 meters deep, but system
shows 1 to 1,20 meters. Heartrate was way up first time.

Marc

S/V Tutti ( Nantucket 33 by Alan Guerny )

It sounds to me that you might simply be bumping into limitations of the technology. It's firing a radio beam and measuring how long it takes to come back. The density of the water, any sediment in the water, movement of the water, all come into play.

Is the transducer pointing straight down, or to the side? That could do the trick.

[Tutti]

Hi Mark

Sediment has come up, and would explain part of observation when moving between sandbanks.
It does not come into play when in a tidal marina and tied up, not moving and still see indications go below 2 mtrs, and not touching.
I do understand how the system works, and transducer is 'straight down' that doesn't explain the irratic indications, unless powerlevel is such it would be impossible to measure correctly when so close to the ground. Any suggestions to different settings (dealer calibration)?

Thnx

Marc
S/V Tutti ( Nantucket 33 by Alan Guerny )

[lancelot9898]

After 20 plus years my old depth sounder(Impulse) started giving erradic readings whenever I ran the diesel and also would not give good reading in shallow waters with muddy bottoms. I replaced that sounder with the Raymarine ST 60 plus this fall and the few times that I've been out it has done well. In my slip the old transducer would not give a reading since the bottom was muddy and the reflected signal was not strong enough to give a reading. That is no longer the case with the new depth finder. Also when under power the readings are now accurate. The most difficult part of the installation was running the cable from the transducer to the pedestal. The yard replaced the old thru hull and installed the new transducer which was difficult to remove due to its location and I ran the wire and installed the pod at the helm.

There were times when the old depth finder was new that the shallow alarm would activate, but that was due to either a fish or bubbles from the prop wash of another boat. It only lasted for a few moments and the reading would return to "normal". I think Raymarine has a help line and that would be my next step if unable to get good readings.