Sonar gone when on plane..

I too have the Lowrance HdS 7 Gen 2, I had similar type issues (also showed some obviously incorrect readings) and got the dealer to change the transducer (same location) and have had no problem at all at any speed (I cruise at 24 knots and periodically blast at 34 knots). Happy to note position and let you know to check it's the same place as yours as we have the same boat.

Would be good to compare where yours is mounted to mine.. Maybe just a repositioning is all that is needed..
 
Mine loses depth sometimes when on plane, but only later in season, which seems to correlate with fouling. There was weed and limey worm deposits on the transducer at last liftout.
I have tried EchoSounder Antifoul this year, and the depth response has been good until the last week or so in a choppy sea.
I shall see how well it has performed at liftout in April.
 
Here's a pic showing mine, The trasnducer is very slightly lower than the line of the hull.

Joka-Tupostwax0710201110.jpg
 
Thanks.. I think mine is more in line with the hull but will need to check, perhaps this evening.. Maybe simply lowering it a bit would be all that is needed..
I've seen several installation guides for transom transducers, and some suggest to keep the lower surface of the thing exactly aligned with the hull.
Some others to keep it slightly lower, but never more than a very few millimiters.
You might wish to have a look at this one from Airmar, which is not a very well known brand but is actually the main OEM producer of these things:
http://www.airmartechnology.com/uploads/installguide/17-247-03.pdf
It's related to one of their transducers, which according to them is good for up to 44 knots.

Actually, as I said before, I never came across a sounder that gave reliable and stable readings at P speed, but I guess it doesn't hurt trying...
...btw, I'm not sure to see the point of looking at the sounder while cruising at 40 kts, generally speaking.
When going at that speed, you must know for sure to have enough water under your bottom and in front of you.
If relying on the sounder readings at that speed isn't looking for troubles, I don't know what else is! :)
 
.....Actually, as I said before, I never came across a sounder that gave reliable and stable readings at P speed, but I guess it doesn't hurt trying...
...btw, I'm not sure to see the point of looking at the sounder while cruising at 40 kts, generally speaking.
When going at that speed, you must know for sure to have enough water under your bottom and in front of you.
If relying on the sounder readings at that speed isn't looking for troubles, I don't know what else is! :)

Haha! That made me laugh as I had the same thought!

Ironically, I also have the Lowrance, but the earlier Elite 5. Mine does works at WOT, but currently that's 36kts as can't quite get 40... yet! :D How accurate it is at that speed, I've no idea as I only really refer to in close proximity to shore or known submerged rocks and at much slower pace.

On mine, I fitted with just under half the vertical profile of the unit itself (not the bracket) sitting below the line of the hull. If you put too high or too low I surmise that you'll get aerated water - in the former instance from the hull and the latter from the unit itself (as well as risking damage to the unit itself - try sticking your fingers in the water at 40kts! :ambivalence:)
 
The answer is probably get a forward looking sonar. Might have a chance of avoiding the rapidly approaching rock!
 
Not really planning on "skimming" through 1m or water at 30kn but still like to have some idea of how much water is below me even outside the harbour.. Having a blank screen and 3 dashes on the depth reading makes me uncomfortable.. :)
 
Just had a look at the boat and I would say the transducer is definitely mounted too high which is probably why it only works at slow speed.. The higher side of the hull is inline with the bottom (not the middle) of the transducer meaning it's well above the hull on the lower side.. So basically the opposite alignment of the "deep-vee" hull image on this page with the entire transducer above the hull line.. http://www.manualslib.com/manual/293058/Lowrance-Skimmer-Transducer.html?page=10#manual

Don't think there is enough movement in the bracket (but will try that first) so looks like I will probably need to remove it, fill the holes and drill new ones to mount it lower..
 
one would think that when on the plane the whole of the transducer would be submerged and the problem would be at slow speed

On mine as it stands I would imagine that on a plane the transducer would be more or less out of the water.. So it definitely needs to be lowered..
 
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