What does this mean? GPSmap 556s

BogMonster · 27 October 2010, 11:34

On my new GPSmap 556s the sounder depth display sometimes (in fact most of the time) just flashes a fixed depth rather than indicating true depth. Doesn't seem to be any pattern as to when (it worked at a variety of speeds/depths at different times yesterday and doesn't work even at rest in clear water so it isn't a turbulence problem) but it just goes off and the "last seen depth" flashes on the display. Rebooting the unit didn't make any difference.

Nothing at all in the Garmin handbook about what this actually means

can anybody with the sounder version of the GPSmap 550/551/556 shed any light on what a flashing depth means? It says that if there is a sounder fault then there is an error message for that but it doesn't seem to think there is a fault. Sounder is an in-hull type fitted near the transom - same place as Chris's Time Bandit - so should not be any problems with the location.

Google suggests all sorts of possibilities from the unit needs a software upgrade (I would hope not, seeing it's brand new) to misaligned transducer (difficult as it's the proper slanted in-hull type and it's glued to the hull) but nothing that looks sensible or likely.

any ideas please?

Channel Ribs · 27 October 2010, 11:38

It does sound like a transducer problem, perhaps an air bubble in the glue?

BogMonster · 27 October 2010, 11:56

Ta - so you think the flashing depth means "not seeing the bottom" - like you would get if the boat was out of the water?

Odd as sometimes it works. I think there is a set of installation instructions for the transducer which I must have missed when I was gathering up the paperwork to bring home last night so will have to read those and see what it says - not sure but I think it is one of the types that you fill up with "something" (seem to remember kerosene?) so maybe the level is a bit low.

Erin · 27 October 2010, 12:02

I had this happen on mine when the oil escaped from the transducer mount in the hull. It basically means it has lost a reliable depth signal, so it would be transducer or wiring related.

jyasaki · 27 October 2010, 16:36

Unreliable signal. Unit lost lock.

Wiring problem, broken/inop transducer (unlikely if it works somethimes), xducer at wrong angle relative to water surface, xducer in aerated water (shows up at speed, but not at rest), poor mounting characteristics (if thru-hull mounted), growth on xducer face, xducer too close to motor (won't show up if motor off), settings on head unit (unlikely if it works occasionally), poor connection between head unit and cable; probably a lot more.

On the software upgrade, a Lowrance unit I had needed an upgrade, and they released another version in the two days it took me to get the one suggested installed. Should be an easy matter to check the Garmin website for current version, and bounce that against the installed rev on the unit.

jky

BogMonster · 27 October 2010, 22:54

Thanks, a few possibilities to look at.

The tide did look to be a bit low in the fitting so I have got some ethylene glycol antifreeze to slosh in there before I try it again, and I don't think the transducer is pointing straight down either which according to the instructions it should be but I don't know how sensitive it is - I did try a steady turn in each direction to bank the boat and it still didn't work so may be the lack of juice.

Chris · 27 October 2010, 23:45

is it a dual frequency unit?

if so you might want to try running it at 200hz only as at 50hz its a much more focused beam for penetrating depth however this does make it more sensitive.

If its not dual then I think you are in the right track with the way it is set in the hull.

Chris

BogMonster · 28 October 2010, 00:35

I tried it on both but neither seemed to work reliably - you could set it to 50 / 200 or Auto.

Will have to wait till the next run out to experiment but Roy says it was working fine when they tried the boat so it may just be the juice being a bit low. Failing that I will have to get a new mounting for it as the one in there is very solidly attached to the hull and I don't think it will come out in one or even several pieces...

Channel Ribs · 28 October 2010, 07:47

If it is mounted in a bath you could try taking it out and drying it off then stick a big blob of blutak on and place that on the inside of the hull, if this works and you don't want the hassle of topping up the bath then and air-bubble free adhesive will make the arrangement more permanent.

Placing the transducer inside a bath of oil is the proper mounting method, but I have installed lots with a blob of epoxy and the technique works well - just be sure you have the right spot on the hull before you commit!

BogMonster · 28 October 2010, 10:21

Yes it's mounted in a 'bath' which is epoxied onto the hull and sits in what (according to the instructions) should be propylene glycol.

Just another thought ... would the silicone sealant method work with this transducer if I tried that? i.e. stick it onto the hull outside the bath and if it works I can leave it there, if it doesn't I can get it off again without too much bother.

The installation instructions are a bit fuzzy and talk about lining up various marks (according to hull deadrise) with other marks and lines drawn on the hull, and though I can't see all the marks, it doesn't sit with the top of the transducer flat which it says it should do so I think the base might be installed slightly wrong.

Channel Ribs · 28 October 2010, 10:28

Quote:

Originally Posted by BogMonster

Just another thought ... would the silicone sealant method work with this transducer if I tried that? i.e. stick it onto the hull outside the bath and if it works I can leave it there, if it doesn't I can get it off again without too much bother.

The removable qualities of silicone are handy, but it is prone to air bubbles. Certainly an way to suck it and see.

As for finding the right spot, aside from blutak you can also use something oily.

Pikey Dave · 28 October 2010, 14:20

Quote:

Originally Posted by malthouse

The removable qualities of silicone are handy, but it is prone to air bubbles. Certainly an way to suck it and see.

As for finding the right spot, aside from blutak you can also use something oily.

Apparently KY jelly works well, errm so I'm told

PS is it an airmar M260 transducer, about as big as a brick & 1KW?

BogMonster · 28 October 2010, 22:14

It should be one of these http://www.sailgb.com/p/Garmin-010-10327-00-transducer/

though the actual transducer is marked Airmar I think - don't have the instructions (or the boat) here to confirm model number.

Pikey Dave · 28 October 2010, 23:14

It's one of these You can download all the distructions there.