Crazy depth sounder

[Wight Leopard]

Soon after starting the engine yesterday to help get round the Manacles the depth sounder started reading from 2 to 65m and every depth in between. True depth was 65m and I'm sure there was nothing fouling the sensor, nor any bubbles or deep patches of weed. The integral speed log worked properly throughout. The sounder had worked fine under both sail and engine on leaving the berth. Twice before in previous years it had done exactly the same thing but then stopped doing it when I isolated the power to the bowthruster. Having sailed all areas from the Thames to Dublin with all variations of sail, power and motor sailing at different revs the only area that this behaviour's happened has been in the vicinity of the Manacles and I'm wondering (not seriously!) if this is an 'electronic Bermuda Triangle' for Raymarine/airmar depth sounders. After a sail of several hours when the sounder worked perfectly I started the engine when the wind died - and the sounder kept working well. The seas had been lumpy the day before it started going crazy.

The obvious suspect is interference from the HT cables but this doesn't explain the long periods (months) between episodes. I'm scratching my head and getting splinters in my fingers. Any ideas?!?

 

[NPMR]

Airmar DST800 of ours failed, after many a troublefree year, with erratic depth readings, whilst the log kept working. Replaced unit with DST810 (800's now obsolete and no longer available) which failed soon after and replaced under warranty. Readings returned to normal.

Couple of points:- 1) apparently they do fail and especially after a decade or so. 2) the 810 will slot into a Raymarine set up without needing any extra working. (Can't remember about keel offsets).

Either way, the different shaped impeller on the later version is an an absolute horror to keep working, as it seems to stop for very, very little reason on our boat. I'm forever having to clean it. Don't know if this is usual.

 

[Sandydog2]

Soon after starting the engine yesterday to help get round the Manacles the depth sounder started reading from 2 to 65m and every depth in between. True depth was 65m and I'm sure there was nothing fouling the sensor, nor any bubbles or deep patches of weed. The integral speed log worked properly throughout. The sounder had worked fine under both sail and engine on leaving the berth. Twice before in previous years it had done exactly the same thing but then stopped doing it when I isolated the power to the bowthruster. Having sailed all areas from the Thames to Dublin with all variations of sail, power and motor sailing at different revs the only area that this behaviour's happened has been in the vicinity of the Manacles and I'm wondering (not seriously!) if this is an 'electronic Bermuda Triangle' for Raymarine/airmar depth sounders. After a sail of several hours when the sounder worked perfectly I started the engine when the wind died - and the sounder kept working well. The seas had been lumpy the day before it started going crazy.

The obvious suspect is interference from the HT cables but this doesn't explain the long periods (months) between episodes. I'm scratching my head and getting splinters in my fingers. Any ideas?!?

Shoal of fish ?

 

[Wight Leopard]

Shoal of fish ?

They'd had to have been the largest shoal since Jesus last went fishing and to have magically disappeared when we shut the engine down! I'm reckoning either interference with other cables or degradation of the original Airmar kit. Intentions are to wrap as much cable as I can in foil and to replace the original sensor and cable later on. I was just wondering if anyone else had had similar experiences, especially off the Manacles. Last year we had no problems there but we sailed, not motored, throughout.

 

[Lucky Duck]

DST800s seem to have a reputation for early failures.

The temperature sensor went after about 5 years and it has been getting steadily worse in terms of not displaying a depth. Getting to the point now that a replacement is necessary.

Depth sounder struggling

 

[Boathook]

My 'raymarine' sounder did that the other week. tried turning on off a few times, but it wasn't until it was off for quite awhile that it then behaved normally. I just assumed that it was the electronics, possibly the
itc-5 getting in a tizz !

 

[Wight Leopard]

My 'raymarine' sounder did that the other week. tried turning on off a few times, but it wasn't until it was off for quite awhile that it then behaved normally. I just assumed that it was the electronics, possibly the
itc-5 getting in a tizz !

Yes - that's exactly how mine behaved.

 

[Alex_Blackwood]

Yes - that's exactly how mine behaved.

If you can have a look inside the unit you may find something simple like a dodgy capacitor or dry joint. Certainly sounds like intermittent fault and electronic components such as "Chips" will usually go permanently "Duff"

 

[Wight Leopard]

Issue sorted, I think. On tracking the route of the transducer cable I found that no less than about 5m of cable had simply been stuffed behind an inaccessible locker where it was free to jumble about in close proximity to all other cables, including the leads to the windlass and bowthruster. The end was wired into a box where it was connected via a number of spade fittings, instead of a modern and simple Raymarine fitting. This presents a number of potential causes for the random symptoms experienced. I got a new transducer with an appropriately-sized cable which I was able to plug straight into the Raymarine STNG system and - so far - all looks good. The 'acid test', however, will come on returning to the Manacles area where 'there be electronic dragons'......