Echo sounder interference

[Silkie]

The new engine is wonderful except that the depthometer produces random readings when it is running.
Those of you with long memories may remember that I had the same problem with the venerable Yamaha which was improved by fitting a couple of ferrite rings to the charging wires between the engine and the battery and finally solved by fitting six. However I now have all six fitted to the same wires on the Tohatsu 6hp Sailpro with no improvement noticeable at all.

Any ideas how to resolve this issue?

[aquaplane]

I was going to be flipant and say turn the engine of to get a good depth reading but thought better of it.

Would it shag the alternator if you put a switch in the charging circuit so you could get rid of the interference when you really need the depth?

[Nick]

.
Fit more ferrite rings?

[sahona]

How do we know if it's alternator or ignition noise? Is there any merit in 'scanning' the area with a tranny radio to try and isolate the source. If there's no activity on forums indicating similar problems with that engine type, perhaps it's the echosounder installation which needs investigated. Mine (ST60) had a cable chafed through against a steering rod. It used to go 'off soundings' regularly until it was fixed, now it's magic. Best of luck...

[Pilgrim]

You could also try and fit ferrite rings to the cable that runs into the ST60 display from the echo sounder. If you put them near the display they should help to filter out the noise before it enters the display electronics. The energy induced into the echo sounder cables will be less than that transmitted from the source of the noise so the ferrite may be more effective in this location.Different ferries have different properties and work at different frequencies. I seem to recall at one point Raymarine used to supply ferrites with their displays so it might be worth trying to get hold of one of these to get the best chance of fixing the problem.

If the display is connected to a seatalk network, try temporarily disconnecting these as I have known noise on these disrupt an St60 display. Again ferrites on these cables close to the display may help.

It may be worth looking at how the cables are run. Check that both the echo sounder cable and the sea talk cables are physically separate If possible from running parallel to any cables that could be causing the source of the noise.

Hope this helps,

Mark

[Silkie]

Thanks for that gentlemen - some good ideas to try.

Not such a wacky idea Bob. Although I wouldn't want to stop the engine, I used to be able to get a reading with the previous engine, before the problem was solved, by knocking it back to tickover briefly.

The manual clearly says that damage may be caused to the charging circuit by running the engine without being connected to a battery but Tohatsu UK forwarded my email to Japan whose first suggestion was to disconnect the charging wires to see if that was really the source of the problem.

I don't know if it's alternator or ignition Bill I just jumped to a conclusion based on the previous issue so your and Mark's suggestion about considering the echosounder cabling makes a lot of sense. I had assumed it would be shielded already but there's at least 6" of cable at the display end that isn't.

I'll let you know how I get on.