Garmin fishfinder transducer doesn't like Duoprop

alt · 15 April 2007, 18:42

My Garmin 240 fishfinder doesn't like my Volvo duoprop.

Saying that, at certain RPM the fishfinder stops working. It's pretty annoying since I can't tell how much water I havre under me. I can only presume that it's the turbulance from the duoprop.

What alternatives have I here? A thru-hull/in-hull transducer? Are they expensive and do they work at speed? I don't really want to go down the through-hull transducer as I dont like drilling holes in my hull, so would be more interested in getting info about an in-hull transducer

Thanks in advance!

jwalker · 15 April 2007, 19:55

I presume the transducer is mounted on a transom bracket. If so, take it off and stick it inside the engine compartment with a big dod of silicon sealer. Make sure there are no air bubbles between the transducer and the hull.

alt · 15 April 2007, 23:08

Quote:

Originally Posted by jwalker

I presume the transducer is mounted on a transom bracket. If so, take it off and stick it inside the engine compartment with a big dod of silicon sealer. Make sure there are no air bubbles between the transducer and the hull.

Sorry forgot to mention that it's a transom mounted transducer that I have, yeah.

OK so you're saying that I should take that transducer and stick it to the bottom of the bilge with silicone? What about the angle of the 'V', will that have an effect?!

jwalker · 15 April 2007, 23:24

Quote:

Originally Posted by alt

What about the angle of the 'V', will that have an effect?!

I've got mine on the side of the V at the bottom, forward of the engine. Just chock it up level while the silicon is setting.

al40 · 17 April 2007, 19:05

I fitted mine to the inside of the hull with Sikaflex and it seemed to work fine. I think the key whatever you do is to ensure there are no air bubbles in the Silicon (or Sikaflex). Take the nozzle off the tube of sealant and put a good amount on the face of the transducer. Pressing transducer firmly to hull will then ensure there are no air gaps.

I believe the recommended approach is to bed it in epoxy resin but I was standing next to the transducer with my sikaflex gun and thought I'd give it a go!

alt · 17 April 2007, 19:52

Interesting! I presume you had to level the transducer?

al40 · 17 April 2007, 22:08

In my case I mounted it in the rear well on a piece of hull just off centre so it was pretty level anyway. I did kind of level it out in the sealent so it was parallel to water surface. To be honest, I don't think it has to be spot on level tho - if you consider that it works well when the boat is rolling. I think the transmission pattern is quite wide anyway. I guess the straighter the transducer, the better the range.

I tried mine in various positions just by filling the well up with water. I believe you can also put the transducer in a plastic bag full of water and place it against the hull at various points untill you get a good reading (the important thing being that there is no air gap between the transducer and hull.

Nos4r2 · 19 April 2007, 09:27

The old trick on yachts with echo sounders used to be to run the transducer in a container filled with linseed oil that was glued to the inside of the hull. Don't know how well it'd work with a transom mounted transducer though-you might have to replace with a through-hull type.

jyasaki · 19 April 2007, 15:55

Nos;

I don't think there's all that much difference between a shoot-through and a transom mount transducer except the physical package. The actual guts are at least pretty similar, if not identical. They should both shoot through fiberglass fine, as long as you don't have air bubbles in whatever it's sitting in (oil or caulk or glue or whatever.)

jky

Nos4r2 · 19 April 2007, 18:08

AFAIK the insides are identical too-but I can see it being a PITA to try and mount a transom mount transducer inside a bottle and keep it at the right angle.

Pete7 · 22 April 2007, 19:58

I don't think the angle matters. Afterall if its over 5m deep what are you worried about and if its less, then 20 degrees of angle ain't going to make a big difference. Even when we are diving, the club one set on an angle rarely differs much to a depth gauge worn by a diver. Pressing it down into a big dollop of silicone sealant should mean you can level it up within reason. Just stick it in and don't worry.

Pete

alt · 22 April 2007, 23:08

Quote:

Originally Posted by Pete7

Just stick it in and don't worry.

Pete

I think i'm going to buy an in-hull transducer and play about with it ie. angles etc.

I'll report back on my findings!

alt · 11 October 2007, 01:03

http://cgi.ebay.com/ws/eBayISAPI.dll...MEWA:IT&ih=007

Hi guys,
Going to go ahead and order the above, Garmin website says it's compatable with the Fishfinder 240. Going to try and get to the bottom of the bilge (well, as close as possible) and mount this using normal bathroom clear (well, not the white stuff) silicone that dries kinda squidgy (But sticks well)

Will try to eliminate all air bubbles and ill give it a day to set/dry... I reckon it should work, any opinions? The bilge is flat so hopefully should get a decent reading

Julian · 11 October 2007, 07:42

We fitted a new Garmin Fishfinder at the weekend, I have fitted the transducer in the engine bay forward of the engine

We made a well out of blue tac right in the v of the hull so its flush then filled it with epoxy resin and sat the transducer in that, gave it a move about to clear the air bubbles and away you go. Very easy to fit.

Julian

MikeCC · 11 October 2007, 14:52

Although plenty of people have suggested silicone sealant, Garmin actually recommend using epoxy to mount the transducer in-hull.

Nos - there's still in-hull types that use an oil bath as well.

Plenty of the manuals also indicate it's fine to use the transom mount type in-hull as well.

Before you go ahead and buy another one, why not just try using it with silicone in the hull anyway?

alt · 11 October 2007, 15:03

Mike, for the sake of $50 I don't want to go messing with seals etc. through the transom (Its on a sports cruiser, not a RIB) so i'm just going go leave the old transducer in place

Julian - What epoxy did you use?

Would something like fibreglass filler do the job? (Like P40... or is it P38... you know the stuff im on about!)

Limey Linda · 11 October 2007, 17:23

The problem with using epoxy/fiberglass is that if the transducer fails you will have to saw cut/grind it out with the potential of damaging the hull. Silicoln works fine and you can remove it with a knife. Suggest a good clean of the hull area to be bonded to. Finish up with a light wipe of acetone. Clean the transducer surfaces to be bonded DO NOT use acetone. Dispense silicone slowly to the area of the hull, do this in multiple stages starting with the perimeter. You have plenty of cure time. leave for at least 1 hour before sticking the transducer down. You can finish off with an additional bead around the tranducer.

alt · 11 October 2007, 17:30

I was going to just cut the bottom of a cylinder of silicone so that when I pour it out it will come out as one big lump, then press the transducer down. Then test it out and leave it overnight to cure. If it still works fine the next morning I was going to give it a very light layer of fibreglass filler to 'secure' it, but i'd still be able to snap the layer if I ever needed to remove/move it .... opinions?

Limey Linda · 11 October 2007, 17:40

Sounds Ok but make sure you do the surface prep. well and you will not need to add any FG filler etc.