Nick's problem with his depth sounder

[Silkie]

I doubt if I could keep you in malt whisky for a "consultation" never mind fees.

[sahona]

I know this is old, but it has the problem history, so maybe we can proceed here rather than on a new thread?
1 Can you test with the fan belt off for a few seconds?
........................Interference?
Yes.....................................no
Other.................................Alternator

To be continued.

[Nick]

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Can you test with the fan belt off for a few seconds?

Great idea but the impeller will be running dry will it not?

[sahona]

If you're high and dry, take out the inpellor, or use a bucket.
Also what kind of sounder is it - LED spinner?

[Rowana]

Remove the hose end from the seacock/strainer and dunk it in a bucket.
Rig up hose to fill up bucket.
Start engine.

I have a Hoselock spraygun on the end of my hose, and the flow can be adjusted to keep pace with the engine suction.

This also flushes out any seawater left in the system. Once I'm finished, I shut off the hose and allow the engine to lower the level in the bucket. I then chuck in a dose of anti-freeze and allow most of that to be pumped through before stopping the engine.

[Nick]

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What turns the impellor then, not a belt? Is it straight off the engine? I can't visualise it from here.

[sahona]

If it's belt driven it won't burn out if the belt's already off. It probably is camshaft driven so give it a bucket of water to drink. The engine will only be run long enough (seconds) to see if the interference is still there or not.

[Nick]

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I'm dubious about doing any kind of a test onshore because the sounder works OK sometimes in water less than 3m even with the engine running . . . .

[ash]

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What turns the impellor then, not a belt? Is it straight off the engine? I can't visualise it from here.

Nick

The raw water pump ( ie the one with the 'rubber' impellor that you would need to worry about) is shaft driven off the engine so you would need to remove the impellor or follow the advice above with the bucket.

The pump which circulates the water/antifreeze mixture around the engine is just the same as the one on your car engine - it works by 'throwing' the water so doesn't easily come to harm unless you run it so long to overheat the seals - but - this pump and the engine won't have been drained and it's driven by the fan belt which is off so no probs.

The prob with a prolonged test is that although you're pumping water out of your bucket it's only really protecting the exhaust - you're pumping raw water through the heat exchanger but you're not pumping fresh so the engine will overheat - just as your car would if you lost the fanbelt.

My apologies if I've oversimplified things - I don't mean to be condescending.

I think that as long as the transducer is inhull rather than thruhull, then this is a job for when you're afloat - not from the engine point of view, but rather because you won't get realistic readings from the transducer .

Ash

[sahona]

If the transducer is "dry", then you won't get any echo return, so nothing will be displayed EXCEPT INTERFERENCE!...... so the test could still be valid. It doesn't kill anything to run it dry.

[Nick]

Transducer is through-hull.

[ash]

Transducer is through-hull.

In that case you had better get busy as soon as it warms up a bit in case you need to change the transducer.

This advice thread must be the longest in history.

Maybe all the experts should hire a minibus, and equipped with hammers of various size, LW radios, oscilloscopes, etc could descend on Balvicar.

After spending the afternoon fixing the problem, they could then spend the remainder of the weekend emptying Nick's drinks cabinet.

Ash (who can't sleep)

[ash]

If the transducer is "dry", then you won't get any echo return, so nothing will be displayed EXCEPT INTERFERENCE!...... so the test could still be valid. It doesn't kill anything to run it dry.

Agreed that it's worth a try - my only doubt is because, IIRC, Nick's 'interference' is wildly fluctuating readings of depth.

As far as I know, if Nick was sailing along the display would be fine, but if he then started the engine and ran it in neutral at above idle then the readings would immediately start fluctuating so it does appear that it's induced interference rather than the transducer struggling to lock on to the bottom.

Nick - correct me if I've described your symptoms wrongly.

Ash

( Still can't sleep - going back to bed to try - using a lappy screen prob isn't the best thing to induce sleep. I had been thinking/worrying about an email which I need to send but I've now got it drafted in Word so hopefully ZZzzzs) ( Joan bought Nytol Herbal Sleeping tablets which seem to work for her but do nothing for me )

[Nick]

Nick - correct me if I've described your symptoms wrongly.

No, that's pretty accurate Ash. The only exception is that the depths seem OK when we are leaving the bay even at moderate revs, then they begin to fluctuate wildly once the depth is over 5m.

When we anchor we use slow ahead (tickover) and get accurate enough depths for anchoring.

Echo sounder blanks nowadays in 30+ metres (used to go to 50) and if anything the problem seems like a combination of old age and interference, unlikely though that sounds.

I will take the through-hull transducer out and have a look at it sometime. Won't be soon though as I am still suffering with the worst cold I have ever experienced - been going on for ten days now.

[Rowana]

I find that a hot drink - Hot Chocolate does it for me - plus reading a bit of a fairly boring book, usually gets me in the sleeping mode, plus don't have a nap during the day if possible. I then force myself to get up at my normal time, even if I'm still knackered.

But there again, everbody is different and it might not work for you.