Depth sounder problem - can anyone help?

[Grahamm462]

Having just bought a Sadler 25 and got her on the water for the first time last week I find the Clipper depth sounder gives crazy random results whenever the engine is running. Fine without the engine. Clearly the previous owner positioned the sounder to close to the engine and it is picking up electrical interference from the engines alternator. Does anyone have any suggestions how I can fix the problem without taking the boat back out of the water and positioning the sounder further away from the engine ? The engine is a Yanmar GM10. Can I get suppressors to fit on the engine ? Would it work ?

 

[Cliveshep]

Firstly, is it a though hull transducer fitting or internal? If internal, bond a bit of plastic waste pipe to the hull with P38, well clear of the engine and underwater turbulence, chuck some baby oil or cooking oil in it and dunk the transducer in that. If external or through hull and you can't extract it without sinking, buy another transducer and fit that in hull as above.

 

[MoodySabre]

You don't say where the transducer is placed. If the random results are just when you are motoring then it could be turbulence - transducer too near the keel(s). If it happens when the motor is running (even if not underway) then it is interference and should be solvable (although not by me).

 

[Grahamm462]

The transducer is the thu hull type. It is positioned within a metre of the engine, The problem only occurs when the engine is running. The previous owner has said he did not experience the problem which confuses me. However, if anyone can advise on how to suppress the interference from the engine alternator it would be great. If this doesnt work I will try the in-hull option. Thanks for your replys.

 

[lenseman]

The transducer is the thu hull type. It is positioned within a metre of the engine, The problem only occurs when the engine is running.

It is probably electrically induced pulse interference and not due to cavitation from the screw I hope?

TEST ONE:
Remove alternator fan belt and run engine for no more than a 30 seconds to a minute to save overheating the engine.
Note whether interference is present.
If the interference is gone, then it is confirmed that the alternator is the source. This is an important test before you can proceed any further.

INSPECTION:

1) Are any of the wired attached to the alternator loose (including any earth bonding wires ie. alternator body to engine/battery)?

2) Do any of the charging circuit wiring run close, parallel or in the same ducting as the transducer wiring?

3) Have you changed, modified or installed any wiring for any device since you purchased the yacht?

4) Have you moved any wiring on the yacht since purchase?

5) Have you removed any wiring since purchase?

6) Have you moved the depth sounder head since purchase?

7) Are any of the wires attached to the Depth Sounder head loose?

 

[Grahamm462]

Thanks Lensman. The only thing I have done since I took delivery a few weeks ago is fit a new Plastimo Contest bulkhead compass. I have found that the new one now no longer has its light working and have established that there is no power in its supply wire. I dont know if it did for the old one ? The other thing with this is that the old compass had wires at the top and bottom but the new one only has a 12V supply wire at the top and no connection for a new one at the bottom. So I have not connected the old bottom wire as there is nowhere to connect it. This wire has no power either ! Other than this I honestly have done nothing else.

 

[DavidTav]

Funnily enough I have had something very similiar happen with my echo sounder when running the engine. It is a NASA Target model. I too thought it was interference from the engine, but I was puzzled as it had previously been ok. I discovered however that it only happened when the batteries were switched to use both. I have two batteries and have replaced them both recently. I now think that this is a voltage issue and the echo sounder gives spurious results when voltage is too high?

 

[rjp]

I have a very similar problem which I posted to the PBO forum about 3 weeks ago. I've now confirmed, as I originally suspected, that it has something to do with the new Stirling alternator controller which I fitted last winter. I find that if I disconnect the field connection, hence disabling the controller, the problem gos away and I get normal depth readings. Reconnect and it goes haywire, hunting around all over the place. Do you have an alternator controller fitted?

I still have some further investigation to do, but may just install a switch in the field circuit so I can switch the controller off when required. What does the panel think? Any suggestions as to why the controller might be causing this? It's fitted the opposite side of the boat to the depth sounder and the transducer cable goes nowhere near it.

John

 

[webcraft]

Had the same problem

We had the same problem, started after we fitted a new engine.
Tried various things, then bought a new unit - exactly the same - and it worked.

Your milage may vary.

- W

 

[snowleopard]

Sounders usually come with a fixed length of cable which you're not supposed to cut. If you have a coil tidied away somewhere you'll have sufficient length to try running the cable another route. That would do the trick if the problem is induced current from the engine wiring.

 

[BruceDanforth]

I'm getting this too with a Nasa Target and a Tohatsu saildrive outboard. The Nasa manual indicates that it is caused by electrical interference. I took my scope down to the boat but couldn't get it to occur with the engine running at cruising speed and the boat pulling against her mooring lines so I'm not sure what's really causing it.

 

[mikeinkwazi]

electrostatic?

Having just bought a Sadler 25 and got her on the water for the first time last week I find the Clipper depth sounder gives crazy random results whenever the engine is running. Fine without the engine. Clearly the previous owner positioned the sounder to close to the engine and it is picking up electrical interference from the engines alternator. Does anyone have any suggestions how I can fix the problem without taking the boat back out of the water and positioning the sounder further away from the engine ? The engine is a Yanmar GM10. Can I get suppressors to fit on the engine ? Would it work ?

I had a crazy depth sounder of the same type and cured it as follows.
My test used a radio tuned between stations, a la Nigel Calder, Mechanical and Electrical Manual, P354 and 212. Much static when motor was running in drive but not with the motor running out of gear. Also the same static when sailing with the prop rotating, nothing when in gear, ie not rotating. I fitted an electro-static eliminator on the prop shaft, wired to the anode and the problem stopped. The depth sounder now works fine! Worth a test with a radio.

 

[Clyde_Wanderer]

I had a crazy depth sounder of the same type and cured it as follows.
My test used a radio tuned between stations, a la Nigel Calder, Mechanical and Electrical Manual, P354 and 212. Much static when motor was running in drive but not with the motor running out of gear. Also the same static when sailing with the prop rotating, nothing when in gear, ie not rotating. I fitted an electro-static eliminator on the prop shaft, wired to the anode and the problem stopped. The depth sounder now works fine! Worth a test with a radio.

Mind me asking where you got your electrostatic eliminator?
C_W

 

[mikeinkwazi]

electro thingy

Mind me asking where you got your electrostatic eliminator?
C_W

M G Duff Electro Eliminator - Only £66.95 - Force 4 Chandlery
Electro Eliminator - Used in conjunction with existing anodes on the boat, the Electro Eliminator is fixed on to the shaft & stops electrostatic radio ...
www.force4.co.uk/1523/M-G-Duff-Electro-Eliminator.html - Cached - Similar

I got mine through the local chandlery at Holy Loch marina, but I looked up M G Duff on the web first as they do two sizes depending on prop-shaft diam.