Depth sounder problem

25931

25931

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Our old NASA sounder appears to be finished - it keeps altering display. Am I right in assuming that the instrument as opposed to the transducer ? If so can I just buy the instrument ? Also wondering about fishfinders. I've never even seen one. Are they any good ? Is it better to buy separate depth & finder ?
Thanks in advance.
 
It could be either the instrument, or the transducer, or even more likely the connection between them.


I like fish finders, not sure why really but they have a pretty display, bleep when they see a fish, and give an indication of the nature of the bottom which is sometimes useful for anchoring.
 
You can buy a basic garmin f.finder kit from garmin for less than £100, I would guess. Dont be confused by f.finder..of course it is a depth sounder just with extra detail. You can usually just display the depth alone in big numbers !, or add in the view of whats underneath. More expensive ones can show the detail (such as fish and sea bed struture) more accurately.
Cheaper ones usually have the transducer off the back of the boat transom..
Try here:
https://buy.garmin.com/shop/shop.do?cID=149
 
NASA (and other) sounders can give odd read-outs, often when there's a lot of soft mud about.

Mine goes mad over deep water but reads OK in shallow, definitely the best way...

The ones I've had have been swap-able, can you borrow someones and dangle the transducer over the stern and try their head on your transducer?

Have you a manual? There is a sensitivity setting which may help.
Is there oil in the transducer housing? (Olive NOT essential)

Nick
 
If you are in the habit of anchoring, I would definitely go for a fish finder. They are really good for giving you a picture of the sea bed. Mine is an optional extra on a Raymarine plotter.
 
You don't need to worry about the transducer mounting; I have a Garmin fish finder ( £93.00 from Force 4, no connection ) which has a transom transducer; after assurance from Old Harry of this parish, correct as usual, I simply stuck the transducer to the inside of the hull bottom with sealant - on the flatter section aft and slightly to one side of the keel.

The fishfinder gives interesting detail, which combined with the 2 alarms - one shallow, one deep - is useful for anchoring, as one can set it to wake up if the boat is dragging in deep water or about to go aground.

It also has a battery voltage readout which might be handy.
 
My NASA unit goes mad when the engine's running but is fine when the engine isn't running, no idea why. I believe the fishfinders do use more power if that's an issue...
 
V1701 said:
My NASA unit goes mad when the engine's running but is fine when the engine isn't running, no idea why. I believe the fishfinders do use more power if that's an issue...
Click to expand...

Suggest you check what you have wired to, is there anything else to the same terminal??
I have had a Nasa unit for years and works well under sail or engine running.

Mike
 
You will notice the fish finders and depth sounders use the same transducer. Current is applied to the transducer, usually peizo electric and it vibrates. This sends sound down and it sends very weak reflections back to the transducer. The transducer sends and listens, the gap depending on the range set. The set then analyses the returned signal and this is where it depends on how much you spent. Cheapies will show fish symbols and the bottom all the way up to white line and other useful stuff. In the small fish finders the current used will be the same as a depth sounder.
 
25931 said:
If so can I just buy the instrument ?
Click to expand...

Yes - you can just buy the display head if you decide that's where the problem lies. I've always found NASA very helpful. I needed to replace a Target 1 with a Target 2 display. They charged the retail price of the complete system minus the retail price of the tranducer (then gave a 10% show discount - every little helps).
 
Definitely fishfinder. It shows the contour of the bottom and mine would show weed growths as well as fish. I don't fish, but it was interesting. Plus of course, the alarms you can set.

Fish.jpg
 
I had a lot of problems with my NASA depth sounder. Originally I was persuaded that it was the transducer, so I changed it. For a short time it seemed to behave itself. Then, after a couple of seasons of not really knowing what depth was under the boat (not too problematic as I know the waters and draw less than a metre) I bit the bullet and changed the whole unit including the display. I actually kept the transducer that was in the boat as I couldn't be bothered to reroute the new transducer.

Guess what, no more problems. the old display had developed a fault.
 
alahol2 said:
Definitely fishfinder. Mine finds hundreds of fish but I never manage to catch any of them.
Click to expand...

lol

My old Nasa went bonkers after about ten year & was highly unreliable for the two meters below the keel which was about all I was really interested in.I checked the connections etc but reckoned it was just a cheap & cheerful unit.In my latest boat I have a seafarer which seems equally useless for as soon as the boat gets moving.
A fish finder seems the way to go so that you can see what you are anchoring over?
 
I guess it depends where you sail, but for me reasonably accurate depth down to 100s of feet is really important. I sail in an area with lots of very steep-to lumps of rock and coral with uncertain charting, so the ability to see as soon as the bottom starts shelving is extremely valuable.
 
As I mentioned earlier, a modern fishfinder transducer can be stuck on the inside of the hull bottom.

If you really want to keep a hole through the hull, most modern transducers are interchangeable but check with the makers of that and the sender unit.
 
25931 said:
I don't want a transom mount. Will any fishfinder work with my existing transducer ?
Click to expand...

I've no idea whether any fishfinder will work with your existing transducer.
When I got my fishfinder, which came with the plotter, a transom mounted transducer was supplied as part of the deal. I just cut off the unwanted bits, and with a short, angled piece of plastic pipe mounted it inside, with epoxy. Works perfectly, to fantastic depths.
 
whipper_snapper said:
I guess it depends where you sail, but for me reasonably accurate depth down to 100s of feet is really important. I sail in an area with lots of very steep-to lumps of rock and coral with uncertain charting, so the ability to see as soon as the bottom starts shelving is extremely valuable.
Click to expand...
My fishfinder was still giving pretty pictures at 192ft depth on Windermere.
 
Before you install a new transducer, place it in a plastic bag and wet the area under the bag (to exclude and air) then move it around to find the best signal.

This avoids the problems associated with poor hull layup or reflections from the keel etc.

Good luck and fair winds. :)
 
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