Garmin 5xxxS flashing depth reading

[Leapy]

Got a Garmin 5xxxS (551, I think, but they're all pretty much the same) attached to a dual frequency Garmin sounder fitted by RC in the transom well. Worked perfectly for three years.

Been out yesterday and today... at low water depth, mostly 10ft or less but occasionally 15ft, the depth reading starts to flash. Sometimes, the reading - whilst still flashing - varies, suggesting it's still reading an accurate depth; at other times it seems to freeze at some 10-15ft figure. Once I hit deep water the problem eventually clears. Back to shallow water and it flashes again.

When not flashing the depth shown appears to correlate with charts.

The Garmin handbook doesn't talk about flashing depth readings.

Any ideas?

[Boats&Outboards]

Has it got any shallow water alarm pre set ? Could be set high hence the problem. Worth resetting or looking into.

Peter ~ Boatsandoutboards4sale ~ askboatsandoutboards4sale@sky.com ~ 07930 421007

[Erin]

On my Garmin, a flashing depth reading means that it has lost contact with the bottom so do not rely on the reading. It flashes the last known good reading until it gets a lock again. Mine doesn't read anything below about 1.5m and will flash if there is excess turbulence in the water too, such as when you're on somebody's wake.

[Leapy]

Originally Posted by Boats&Outboards

Has it got any shallow water alarm pre set ?

Hi Peter...that was my first thought too, although that usually shows as a "Shallow Water" pop-up. I did have it set but disabling it made no difference

[Leapy]

Originally Posted by Erin

On my Garmin, a flashing depth reading means that it has lost contact with the bottom so do not rely on the reading. It flashes the last known good reading until it gets a lock again. Mine doesn't read anything below about 1.5m and will flash if there is excess turbulence in the water too, such as when you're on somebody's wake.

Hi Erin...Yes, on the very few, very short duration occasions this has happened in the past, I assumed depth contact had been lost in murky shallow water: it usually always happened in the Marina. The last two days though it's been flashing more than not. Even when running In 60ft of water it would take a few minutes to get its act together.

Not much chance of running in someone's wake today...the Fal Estuary was as good as deserted.

[Erin]

What type of transducer is it? Does it bayonet into a housing bonded to the hull. If so, then it's possible some of the glycol has escaped. This happens to mine on bumby journeys as the o-ring is obviously not a good fit. I just top it up occasionally.

[Leapy]

Originally Posted by Erin

What type of transducer is it? Does it bayonet into a housing bonded to the hull. If so, then it's possible some of the glycol has escaped. This happens to mine on bumby journeys as the o-ring is obviously not a good fit. I just top it up occasionally.

It's Garmin transducer bonded to the transom well...it looks like it might also be designed for bolting as there are moulded in serrated mounting or swivel lugs. Other than that, I don't know much about it.

Glycol top-up? What should I be looking for and where?

[Erin]

This is what I have P79 ducer. You unscrew the top and put glycol in or some other inert oil type liquid such as castor oil. It provides the continuity for the signal between the transducer head and the hull. Any air in between the two will stop it reading properly.

[Leapy]

Erin, thanks but mine looks nothing like that. But the principle of what you say may hold true. I'll take a closer look tomorrow.

Thanks

[jyasaki]

Ditto that it sounds like it's losing lock. Is the hull dirty, by chance? Or has the head unit been switched to a single mode rather than auto?

When it happens on my Lowrance, it's usually due to the xducer being kicked up, but that won't happen with yours.

jky

[Pikey Dave]

Could be the bond between the hull & txer that's starting to come apart. Try wiggling the transducer & see if it's loose or comes off. It will need cleaning up & rebonding. Epoxy is good for this.

[Leapy]

Originally Posted by jyasaki

Ditto that it sounds like it's losing lock. Is the hull dirty, by chance? Or has the head unit been switched to a single mode rather than auto?

jky...the hull's not dirty but I did notice when playing with the sonar displays that only the 200MHz ident was shown. If it was set to 'dual' I guess I should have seen 200/50MHz (think it's 50 from memory). I'll check shortly...

[Leapy]

Originally Posted by Pikey Dave

Could be the bond between the hull & txer that's starting to come apart. Try wiggling the transducer & see if it's loose or comes off.

PD...tried that, it's well and truly stuck

[Leapy]

Originally Posted by Pikey Dave

Could be the bond between the hull & txer that's starting to come apart. Try wiggling the transducer & see if it's loose or comes off

PD...tried that, it's well stuck

[jyasaki]

Originally Posted by Leapy

but I did notice when playing with the sonar displays that only the 200MHz ident was shown. If it was set to 'dual' I guess I should have seen 200/50MHz

50kHz/200kHz. You're not running a microwave

200kHz should be what's in use in shallower water. Less penetration but greater sensitivity. Lower freq for deeper water. So that's not it.

jky

[Leapy]

Originally Posted by jyasaki

50kHz/200kHz. You're not running a microwave

Microwave...:-) I knew that...

So, been out again today...all the settings on the 550s that can be at 'Auto' are at 'Auto' and the transponder is well and truly stuck down. The hull is squeaky clean. The 'Auto' setting is where the 550s has always been.

Tried various manual settings: no change.

Changed frequencies: no change.

The 'Gain' was set at 70%...I upped this to 90% - thinking gain might equate to signal strength - and all was fine for about 30 mins and then flashing mode came back and nothing I did could take it out of that mode, including a restart.

So...no further forward. One other change point comes to mind though. The transponder is on centreline in the transom well. Since last use in August we've had a full length keel guard fitted and so the transponder now has to 'see' through the keelguard. I know the keelguard will attenuate the signal but we're not the only RIB in the world with a full length keel guard so I can't think this is the issue.

I'm batting a variation of this post off to Garmin Tech Support to see what they say. Still interested in any other opinions though please

[Boats&Outboards]

Shame you don't know anybody will similar rig who could try your head on their transducer. That would quantify the fault and help narrow it down for you. At least then you'd know where to be looking to fix the problem.

Let's hope tech have a solution

Peter ~ Boatsandoutboards4sale ~ askboatsandoutboards4sale@sky.com ~ 07930 421007

[biffer]

Free up you're pm box pete

sent from a remote device

[Boats&Outboards]

I'm trying. I wish I staggered these now it's gone crazy

Peter ~ Boatsandoutboards4sale ~ askboatsandoutboards4sale@sky.com ~ 07930 421007

[Erin]

Originally Posted by Leapy

Still interested in any other opinions though please

I presume you've checked the wiring and undone and remade the connections into the back of the display unit.