fishfinders.....

[Johan]

I have a transom mounted transfucer for my garmin 160 blue fishfinder and I have experienced that I cant read bottom structure above 5-7km/h (about 4 knots).

What max speed do you guys get when finding reefs? I have tried using only the engine furthest from the transducer (to reduce noise) but it makes no difference.

Does using some noise rejection cause you to loose detail on fish?

Also.....what does fishfinders pick up besides fish? Do they write dolphins, seals, sharks and crayfish?

Finally - 50khz supposedly is better for deeper water. How deep is deeper water?

 

[miles]

Hiya

Your transducer is probably mounted at the incorrect height. When AIR gets under the transducer, it will stop reading. When going faster than 4knts, you'll most likely have your transducer OUT of the water, thus not working.

Most transducers are adjustable, so simply move it lower down. Simple to do, normally just requires a screw-driver. Check the installation guide for your unit, but most need to stick out 1cm BELOW the hull.

Take some pictures of where its mounted. That will assist us all in helping.

My Furuno FCV620 reads bottom continuously, up to about 35knts. After that i start getting air under the spot where the transducer is and i only get broken bottom readings.

On my old boat, my Furuno GP7000F would read up to 25knts.

I've seen sharks, whales, seals and dolphins on my echo, don't know about kreef though!!

 

[Johan]

Miles, I think you are spot on there. As I increase speed I get this intermittent bottom structure which is probably as the air starts breaking up contact between the water and transducer.

I added two photos but they have been taken now and its night time. Hope you will be able to see.

Thanks again for calling me to give me advice on my fishfinder. REALLY appreaciated!

 

[Johan]

Second picture

 

[miles]

I can't see clearly, but it does look like its mounted a bit high. Loosen the three screws, and simply push the transducer down, until it can't go any further, then re-tighten screws. Should work better!!

 

[Johan]

Miles, its about 3cm above the hull. I will move it until its about just under the hull.

 

[miles]

Yip, it should stick about 1cm BELOW the hull.......

 

[Patrick]

Is it just the photo or is your transducer also mounted at
an angle? It should be parallel to the floor if it isnt.

 

[Johan]

Patrick you are right, it was mounted skew as well. I am really really pi$$ed off at the people who did this install years ago. The whole of the boats electronics was buggered and I rewired everything except well the transducer! It was only until recently that I fished with Catch22 that I realised that my fishfinder setup isn't worth crap! Ive been battling with reading proper fish arcs since I can remember and now I know why!

You would expect a company to at least do something like that properly. But now I know just so much more about properly mounting a transducer. I will NEVER again let anyone else do any electronics on my boat again!

 

[Johan]

The problem now is that its still too high. It only moved about 1cm and the lowest part is still about 500mm above the hull. Since its a V-hull it should be mounted so that the highest part of the transducer is just below the hull -  as per the furuno diagram.


I don't think its gonna be possible to get it any lower without redrilling the holes and that is something I don't wish to do now since I am thinking of buying a furuno ls-4100.

 

[Johan]

Between Garmin, Lowrance and Furuno, The Furuno manual gives the best detail on mounting a transom transducer. This is a diagram showing the difference between flat hull and v-hull mounting:

 

[Johan]

I have leveled the transducer from port to starboard (beam) level relative to the boat since I will assume it will lie level in the water.

The bow line level I am not to sure of.....how should I go about doing that while the boat is on a trailer?

 

[Patrick]

Johan, i know its not what you want to have to do after "professionals" were meant to do the job properly, but what about making a short S/steel extension plate that attaches to the transducer bracket and then screws into the hull using the same holes.
You would then just have to counter sink holes in the S/steel plate for the bolts so that it still fits flush against the transom.

As for the bowline level, i measured mine by just dropping the jockey wheel until the hull is more or less parallel to the floor and then also setting the transducer parallel to the floor. Does your transducer have a sort of a cog that you can click different positions into? You could then make finer adjustments to it on the water whilst watching the finder, until you find the right spot, although that shouldnt be neccessary if you get it parallel to the floor as mentioned.

I may be wrong, but i dont think that setting is so critical if you take into account that the bow level is constantly changing as you move across water.

 

[Johan]

Patrick, that is a very good idea! Thanks for the info on the level, I will set mine the same and then see what happens!

There is no cog on the bracket though! I will let you know how the bracket works out!!

Professionals?..........Pfffffff, I would rather not say anything!

 

[Patrick]

Come to think of it you could probably even just use a hard plastic for the plate instead of S/steel. The length will be short anyway so it it wont flex, and it'll make drilling it easier and cost less.

 

[Simen]

Again it proves what Sealine is all about.You have a problem and somewhere on Sealine someone will have the knowledge to help.

 

[Johan]

Found a nice thick piece of stainless in the scrap. Not sure if its 304 or 316 but I suppose either will do in the sea?

After some grinding and drilling it turned into a very usefull bracket! Will post a photo of the boat tomorrow since its dark now.

The transducer will now travel from just above the hull to about 2cm under the hull!

Thanks Patrick for the idea!

 

[Patrick]

Jeebers, thats a nice piece of crafting you did there Johan, and noggal quick too.

Glad i could help.

 

[Johan]

Thanks Miles and Patrick! You guys really helped me out here.

The fishfinder is now PROPERLY mounted. Set perfectly level with respect the the boat and I am sure it is now at a proper depth.

 

[Johan]

Transducer on mounting