Fish finder transducer mounting: HELP!

Bodach na mara

Bodach na mara

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OK, this has all been done before, but I need advice on how, or if, I can mount the transducer inside the hull. I have bought a Garmin 140 fish finder and thought I knew what to expect until I opened the box. Instead of the usual round, flat-bottomed transducer I was expecting, there is a funny-shaped thing with a curved bottom designed for the transom of a motor boat. This will just not work on the transom of my Westerly Renown, as it would be either out of the water or under it as the waves went past.

Has anyone succesfully mounted one of these inside the hull? If so, where. I had hoped to put it up forward on the centre-ling ahead of the keel, but the thickness of the hull there and the limit of 20 feet in the cable probably rule that out.
 
put simply - it will work through the hull. Quite literately stick it in a piece of plastic pipe the dia. of the transducer (waste pipe/plastic bottle cut off anything that you can shape to your hull and seal) , fill with any light oil , pop the transducer into the well and Bingo. Just did same with fishfinder I bought as backup to echo sounder (more novel,cheaper).
 
I have just used epoxy (Araldite) to glue mine directly to the inside of the hull. Providing there is no air gap (bubbles) it works fine. Just make sure it works in the place you want it to before commiting to glue.
 
Exactly the same as my fishfinder. It is a funny shaped transducer -obviously designed to be stuck on the outside, but I bedded mine onto a dollop of epoxy thickened up with microballons. I haven't run aground yet.
 
So how thick was the hull in all these situations? The answers may help the original poster to decide where to put his.

PS Ours is siliconed onto the hull inside the engine bay and works through atleast 100mm of fibreglass.
 
Thanks all. Great advice so far folks, but microballoons sounds a bit strange. Usually it seems you need to prevent air bubbles. However, if it works, it works. Obviously there will be an echo form each side of the hull skiin but as they are both so close to the transducer, I assume they are not registered as objects.
 
First fill a bag with water, then move it about the bottom of boat, with fish finder thingy pressed on top of it. It can be a devil of a job finding a good place. An inch can make alot of difference. Mine works fine now, but took some time to find a position.
 
I mounted mine through the hull like the old fashioned transducer. It meant shaping a bit of hardwood and slapping sikaflex around but it is fine!
 
Re: Fish finder transducer mounting: HELP!

Blue-tack. Press on to transducer and move around until you get the best signal return.

Can then be mounted permanently by any of the above methods.
Donald
 
Re: Fish finder transducer mounting: HELP!

Just a thought in case -even after all of your careful trials you epoxy it in and it doesn't work! Wrap the transducer in electrical tape before you glue/silicone it in. It has no effect on performance but its a lot easier to remove. Been there done that (I think my silicone had bubble in it).
 
Re: Fish finder transducer mounting: HELP!

Thanks again, there are a lot of useful tips here, but I don't really fancy the hole through the boat Noddy.

Cutting the awkward (sort of retangular) shape would be hard in the Renown hull, which is about 20 mm thick, and I would worry about a hole 3 inches by 1.5 inches being blocked with a bit of plastic (the transducer) held in place by Sikaflex.

For location, the water bag idea means that I will wait until I am afloat and experiment. There is a spot that attracts me under the prop shaft, where the hull is like a u-shaped trough lying with the bottom horizontal. It is not far from where the instrument is to be mounted. The only caveats are the possibility of vibration interference, oil driping on the cable, and making sure the cable is well clipped back to he structure.
 
Re: Fish finder transducer mounting: HELP!

I found a transducer similar to the one you describe on a Garmin GPS/fishfinder (I really bought it as a GPS and the transducer was a bonus). Handbook suggested various ways of mounting, including epoxy to the floor to work through-hull, having tried out various locations first using Blu-tak or a small puddle as described above. (Through-hull does not work, it seems, if the hull has foam or similar core.)
Mine's epoxied in just ahead of the keels. Works fine.
 
Possibly. My reason for the vagueness is as follows.

I have 3 depth instruments: a conventional depth sounder (DS), a fish finder (FF) and a forward looking sonar (FLS). The DS and FF seem to coexist quite happily, but the transducers are about 2m apart. The FLS and the FF are also happy to work simultaneously, but again their transducers are about 2m apart. The FLS continues to work happily with the DS on, but not vice versa: on switching on the FLS the DS "goes on holiday". The transducers are about 100 mm apart.

The transducer separation distance might be relevant, or it could be a complete red herring. IIRC both FLS and DS use 150kHz, FF uses 200kHz. The DS with an external transducer is much less sensitive than the FF with its transducer glassed to the inside of the hull.
 
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