Depth readings - Lowrance 330C

My Lowrance 330C goes crazy above about 18 knots - gives a load of black lines on the fishfinder screen and no longer gives a meaningful depth - number flashes). Sometimes I have to switch off and switch on again even after slowing right down - it fails to re-acquire the bottom properly even at slow speed after a fast run.

Is this ' normal '?

Thanks

Bruce

Could well be down to position / installation of transducer. Have a look at other threads on this subject and if this sheds no light on it post a pic of your tdcr.
Cheers,
Mark

Bruce, as you know I've got the Lowrance 320 which is essentially the same unit as yours except without the colour screen. The transducers are identical though. Mine gives depth readings and perfect sonar picture all the way up to WOT. Lowrance sounders are well known for their great high speed readings so it must be down to the install. It sounds like you are getting some turbulence or maybe the sounder clears the water when you are planing through the bump stuff.

Heres a pic of how I've got mine mounted if it helps.

It is certainly turbulence related. Here is a piccy of my installation. What do you think?

Also, whenver I get it onto the trailer it is in a semi up position as though the water flow has pushed it upwards

Bruce, it is in a semi up position as a sort of collision protection system, it pops up if it hits anything, but can also pop up after a big jump at 30-40kts. You can remedee this by tightening up the nut & bolt either side of the rubber washers. The position of yours does look to be slightly higher up the transom than mine which might just be the cause.

Also you could try increasing the ping speed from the default 50% to 100% on the sonar. If you do this you may get a second bottom echo cluttering the screen which can be eliminated by decreasing the sensitivity slightly.

HTH!!

Steve

Mine doesnt work over about 10 knots if it makes you feel any better Bruce :p

Looking at the manual, it seems as though swginn's is placed in between two of the 'strakes', whereas mine is placed quite close to a 'strake'. The manual - see attachments - implies it should be mounted between these strakes. Is that my problem? Simmons0, where is yours mounted?

Bruce - I would have thought that your depth transducer is quite simply just too close to the speed paddle wheel. Try taking the paddle wheel off temporarily and see if it improves?

Exactly the same place as yours bruce. Under the outermost "strake"

Well, Kevin moved the transducer, following RichardB's comments, on the basis that the paddle wheel stirred up the water.

It worked - thanks Richard.

Now I have another problem. The transducer does not stay in the deployed position when yours truely is out in Solent chop and we are going at 30 knots. Something to do with attitude, in both senses of the word.

Dare I tighten the screws on the bracket and risk losing the whole thing to an obstruction?

Cheers

Bruce

Stick it inside the hull and be done with all this nonsense. Do a search to find out how.

If it's any consolation Bruce I've never had a boat that had a depth sounder that worked above 15knts!

In fact my new one doesn't either, so will try a few things suggested here.

JW - Through hull transducers are just another expense and you have to start drilling holes in the deck of your loverly shiny new boat. Something that not everyone is comfortable with.

JW - Through hull transducers are just another expense and you have to start drilling holes in the deck of your loverly shiny new boat. Something that not everyone is comfortable with.

Just glue the normal sensor in the transom well using expoxy or silicone (yes I know the manual says not to use silicone sealant but it works quite well) Lowrance are quiet powerful sounders so will fire through solid GRP. We did this to the club dive boat as a temporary measure for an afternoons diving, that was in 1996 and its still there.

Pete

Just glue the normal sensor in the transom well using expoxy or silicone (yes I know the manual says not to use silicone sealant but it works quite well) Lowrance are quiet powerful sounders so will fire through solid GRP. We did this to the club dive boat as a temporary measure for an afternoons diving, that was in 1996 and its still there.

Pete

I stand corrected.......sorry JW!

I thought they had to be mounted in the hull, as normally (for the boats that have them) there is a pocket made in the hull specifically for the purpose. I didn't know your could use a transom transducer to shoot through the hull, I'll give that a try if all else fails!

I stand corrected.......sorry JW!


No problem.
:)