North Australian FISH FINDER TM forums

Howdy FFFers,
Was helping a mate on the w/end and we were looking to put the transducer inside the hull. Has anyone done this with good success?
We filled the bottom of the hull with a couple of litres of water to give it a good medium to shoot through but were still getting a lot of feedback from the hull. It worked perfectly when we just dropped it over the side.
Bit of background info - boat is 14.5m maybe 7/8mm thick and has just been antifouled and we were using a Lowrance x5 colour sounder. Dropped the Hz to 87 as 200 wouldn't work.
If we got it working with the water we were going to use a huge glob of silicon as the medium and also to glue it in place. I have used this with good success on my little car topper so it wouldn't get knocked off while transporting.
Any of you technical types out there have any other solutions it would be greatly appreciated.
We are trying to avoid putting a new hole in the hull if possible.

Cheers
Shawn

Pretty sure you will need a thru hull transducer

How about welding a tab on the back of the transom and mounting it through that? I have seen a few about and I have a similar setup that works very well.

Dan

We looked at adding a tab to the back but its a tri hull boat with twins on the back and we think that there will be too much wash and interference with the shape of the hull. Additionally it is now back on the water so welding is going to be hard without putting it back on the hardstand. May have to "dry dock" it on a sandbar for any mods to underside of the hull including a through hull transducer.

Air bubbles are the enemy of a good return signal. Provided the transducer stays wet and free of air bubbles you should not have a problem. Fixing to the pods or jacking plates where forward of the outboards should not cause you a problem. The install manual recommends this location.

If it helps at all this is how mine is setup and I now get good returns to 60 km/h. Dan

What's the hull made of? Metal or fibreglass?

Aluminium

i don't think ally is the best option for a thru hull.... I've mounted one in a plastic kayak using selleys all clear, putting a big blob and making sure theres no bubbles. Gently sit it in the silicone but try not to create any air pockets between transducer and silicone..
at the end of the day you can try it without extra holes ( just run the cables to it) and test it out... if it works, great. If not it'll only cost you the price of the silicone.
From the install too just make sure you do it level

There are going to be pretty big losses in signal trying to fire through metal. Double losses as the signal has to go out and then return.

I've put a transducer inside an aluminium hull before but it was only for ascertaining depth. Bedding it into a big glob of silicon straight onto the aluminium. Too many losses to get any helpful detail. 7 - 8 mm aluminium is pretty lossy!

Firing through fibreglass is ok as the losses are much less.

If you insist on firing through aluminium then you need to get a much more powerful sounder to try to make up for the losses.

My advice is don't unless its simply for depth (and shallow at that).

I'd put the boat on the hardstand, cut a square hole and make up a little box with the transducer head level with the bottom of box flush with level of hull.. Silicone it in from the bottom.

Then you'll have a sounder that works properly, doesn't protrude, maintains the integrity of the hull.

Thanks for your input fellas, will have another look at the boat on the weekend

ronje wrote:There are going to be pretty big losses in signal trying to fire through metal. Double losses as the signal has to go out and then return.

I've put a transducer inside an aluminium hull before but it was only for ascertaining depth. Bedding it into a big glob of silicon straight onto the aluminium. Too many losses to get any helpful detail. 7 - 8 mm aluminium is pretty lossy!

Firing through fibreglass is ok as the losses are much less.

If you insist on firing through aluminium then you need to get a much more powerful sounder to try to make up for the losses.

My advice is don't unless its simply for depth (and shallow at that).

I'd put the boat on the hardstand, cut a square hole and make up a little box with the transducer head level with the bottom of box flush with level of hull.. Silicone it in from the bottom.

Then you'll have a sounder that works properly, doesn't protrude, maintains the integrity of the hull.

Sounder box.JPG

Do you get much interference from turbulence from the hole in the bottom?

No

You fill the gap with silastic and smooth it across the face of the transducer so the face is exactly level with the hull. No turbulence on the face then

If its a round transducer get a bit of aluminium pipe of the sufficient diametre to take the transducer and cut a suitable size round hole to suit the pipe. Weld the pipe butt end onto the hull so the pipe extends up into bilge. Measure the distance from the face of the transducer to the sealing ring on the transducer shaft. Cut the pipe at that point and then weld a bit of flat aluminium across the bilge end of the pipe. Cut a mounting hole to fit the transducer in the pipe.

Basically all you've done is shift the through hull transducer mounting hole up into the bilge and the transducer face then mounts flush with the hull.

I'll get a pix of one for you.

Thanks for taking to time to explain it Ronje, much appreciated

Try this.

http://www.bertram31.com/proj/tips/in_hull_ducer.htm

2 things about how this fella went about it.

Firstly the size and shape of the box he built corresponds with the size and shape of the transducer he wanted to use.

Secondly he used a fibreglass box. He must have had a fibreglass hull.

Make your box (if you decide to go ahead) out of aluminium and weld it into the corresponding shaped hole that you make in the hull. Al comes in enough shapes and sizes (round pipe, square or oblong cross-section) to find exactly what you want.

I'd use a "puck" style transducer (shaped like a ice hockey puck) of right freqs for sounder. Airmar from USA are big noise in transducers.

Also think about what u might need in the future eg a transducer broadband enough to fully use the advantages of CHIRP technology.

Be interested to see how it pans out if you go ahead.