Fishfinder Transducers

Hi all, :rolleyes:
I am looking at fishfinders and have just sussed that there is a choice of through hull and transom mount. I am not even sure a through hull is compatible with a rib.... but it if was, is it not prone to damage from beaching etc? Whilst I can see a transom mount will just fold back if it is knocked by something, is this more robust? Is high speed with water impact going to cause damage?? I would have thought mounting the sensor as far forward as possible would give that bit more warning at low speed?

Anyone got any opinion, experiences or fact even?!?!?

Am currently looking at Garmin models (incl GPS if I can find a bank to rob :eek: !) And before anyone mentions it, forward looking type are faaaaaaaaaar too expensive.

Thanks in advance...

Andy.
z

I think you'll find that most RIBs use the transom mounted jobbies. We do for an Eagle fishfinder. No problems with this just make sure that the transducer is mounted correctly according to the instructions - out of the turbulence of the engine and low enough to read when you are on the plane. Apart from that you should have no problems.

Cheers, Alan

I use the Garmin 235 sounder with a transom mount transducer. I've covered a few thousand miles with it now with no problems. The only thing you need to do is keep a close check on the tension screw to allow the unit to stay down in rough conditions, otherwise they tend to pop up too easily.
It would be of more benefit if you could have the transducer mounted further forward in the boat but for obvious reasons i don't think a through hull transducer is suitable in a rib.
I think the RRP for the Garmin 235 with sounder is around £700!

I was looking at Garmin 168 or 188 (due to be released now). Price looks pretty good - fron the US or Canada! ;)
Anyone had any experience importing from either? How likely will customs or whoever get me for import duty? and if so I am guessing that is just vat at 17.5%??
Or is there anyone who travels across the pond that could help out, or anyone that lives over there that can send a present ;) -don't think import applies then???
Guess I need to do some more homework on this one...
Cheers for all the replies so far.
Andy.
z

Import duties can differ! Best to contact a company like DHL, UPS or DANZAS they can sort it all out sometimes it cheaper than 17.5%.

I use the Garmin 160 Blue fish finder which works fine NOW.

The Garmin manual state a quite short distance min from the prop arc. I followed these + 2" and it would not read at speed. I have now move the transducer as far away from the prop as possible and still be in the water on the plane and it works fine.

I tested the second mounting point (did not want more holes to fill in the transom) using a wood strip 2X0.5" which I mounted the transducer to then held this in place on the transom with a G clamp. Once I found the best spot I fitted the transducer direct to the transom.

Apart from these dubious Garmin instructions have found the Garmin 160 Blue fine.

I have the Garmin GPSMap235, with an Airmar transom mount transducer supplied as standard by Garmin.
Works OK, but I was not comfortable with the standard plastic mounting bracket on the transom. This only kicks up if you hit something and does not give the facility to hinge the transducer up for beaching. I spent an extra 15 pounds for the stainless steel mount which allows you to swing the transducer up out of the way of you want to beach the boat. It is also considerably more robust than the plastic version.
Airmar are an American company but they have a Distributor in Denmark who is happy to do business in Euros and posted the stainless bracket to me by return. The mounting holes for both are the same so you can 'upgrade' later without peppering your transom with holes.
Rgds
Nigel

anyone know how i could get a garmin gpsmap 168 repaired? water has gotten into it and corroded the contacts where the power supply meets the pcb. waterproof my arse! anyway any ideas?

The first place to try had got to be Garmin. They've got a good track record of replacing kit if it's under warranty -- if not they will probably still be able to help.

John

You can get Garmin UK on 01794 519944

Always found them helpful.

so i took your advice and rang them, dubious enough as the unit was bought second hand AND we'd attempted to repair ourselves. also not currently in UK so what service did I get?

1. Friendly. They answer the phone and dont leave u listening to greensleeves for 10 mins b4 you talk to an imbecile.

2. Efficient. Turn around in 10 days

3. Effective. Replaced parts with new, giving perfect instrument.

4. Fairly priced. I got the distinct impression that they weren't trying to 'charge what the market will bear'

I cannot comment on what gps is best for any particular application but I think GARMIN's repair service is a serious plus for anyone considering buying. They dont wash their hands of you once you've bought.

Agr

I have a Garmin Blue 160, and this seems to work fine. The transducer is transom mounted. The Blue is a new verion for seagoing use - and seems to have advantages over the previous 160s I have seen.

One caveat with ordering from the states - I recently ordered some things and was assured that import duties etc were taken into account ith the price quoted - only to have an additional £75 bill arrive some 2 months later. The explanation from customs was that they do not have the time to check all parcel arrivals, and they scan shipping notes as they can -sometimes much later on, and bill for any duties due! This came as a bit of a shock, and totally altered the advantage of buying from abroad.

Graeme

Back to the original question of transom mount v 'thru the hull'. I had my first 'fish finder' on Prime Rib with the transducer mounted on the transom. This was fine at low speed but useless on the plane. (OK, I have a twin set-up so the transducer was not really in the right place, but whatever... it didn't work very well when running fast.)
Then, with my second 'fish finder' I decided to mount, thru the hull. I cleaned off the bottom of the rear sump, (which on Prime Rib goes right to the bottom of the boat and is just solid hull through to the water) and araldited the new transducer to it. It works a treat. No problem from fouling at the transducer is inside the boat. So long as you glue to a solid piece of hull, (Fibreglass), i.e. not air pockets, the beam will penetrate through to the water.

Have fun

Mike C

the transducer on my Ribcraft 4.8 is in the same place as Mike's (in the rear sump). I have tested the reading with a lead line and found the two to be within 0.2m of each other at various depths from 1.0m to 10m. Out of the two I would prefer the readings of the fishfinder as I'm never too sure when the lead has hit the bottom (as they say ;) )

Ribald, Did you drill a hole in the sump area of the hull or did you arrange the transducer like Mike did. Hey, what does "araldited" mean. Is that a British product? How far from the center line of the boat did you mount the transducer. Any other ideas. I'm mounting a Garmin 188 transducer on my Ribcraft 4.8 next week.

Nick

For 25 yrs we have simply dropped the transducer in the sump of the fast fishing boats we have had and left it there without sticking it down - as long as it is single skinned and there is an inch or so of water in there its fine. We put the transducer in the sump of the ocean pro and screwed it there with the mounting bracket on the inside of the transom when we first had it to avoid holes thru transom and vulnerable bits on the outside for beaching. Worked ok (there is always some water in the sump) but we needed to move it but still wanted to be able to put it in another boat if need be so we stuck it in with silicone sealant. Totally against the instructions (loss of signal etc) but it works just as well and we have had one stuck in the Bayliner ski boat (been there 2 yrs now) in just the same way and its been no problem. If we want to move it to another I trust we will be able to peel the silicone off it! Our local boat angling club launches off a stoney beach and all their transducers are inside in the same fashion to avoid damage if they have a heavy landing on the beach.

Nick,

My transducer if fitted in the sump - no holes were drilled through the hull that I can see (I bought the boat second-hand so did not see the original installation). The unit is fitted on the lateral center line of the boat at the lowest part of the sump just in front of the transom drain plug. (Be sure that you can remove this plug after fitting.) The only prob with this position is that I have dificulty in getting the hull/deck drain plug out.

The previous owner did tell me that it was necessary to keep a small amount of water in the bottom of the sump but I'm not too sure why - anyway there is always some in there anyway.

Araldite is a two-part adhesive that we have over here and will stick almost anything to anything else for good :eek: I think you have a similar product over there called JB Weld. However, I think Wavelength's idea of silicone would be better for easier removal if needed.

Good info. Thanks. I've seen installations in which the transducer is mouted in a plastic half dome which is up against the glass hull. the dome is filled with water or, I think, mineral oil. The half dome installation makes it possible for the transducer to point straight down even though the hull surface its mounted on is angled with deadrise. Does that make any sense at all? These inside solutions sound far better than mounting externally on the transom. which seems vulnerable to any number of hazzards.

I know about JB weld. Its a filled epoxy. I think I'll email Airmar, the transducer manufacturer for Garmin, for their 2 cents on the matter.

Nick

Ribald - the reason for the water is that it will not sound thru air - in fact the echo that comes back from fish is from the gas in the swim bladder rather than the flesh. When fitting with two part epoxy (or even the forbidden silicone!) it is important to ensure that there are no air bubbles in the mix. We have trouble sounding if we trim the motor out to excess due I am sure to air turbulence entering the water under the stern

Here is the website of an airmar transducer which seems ideal for a rib application:
http://www.airmar.com/whatsnew/f_whatsnew.htm

They're sold to the retail market through Gem Electronics 803-394-3565

Nick

Nick,

I will be interested to know what info you get back from Airmar.


Dave,

Thanks for the info - all is now clear and explains why the FF goes doolally when going astern.

Sorry for not explaining Araldite! Basically by using this 'epoxy resin', you are bonding the transducer to the hull, so that it all becomes ‘one’. You don’t need to drill any holes but it does need to be down to the inside of the solid bottom of the hull, (hence in the sump). As has been said, provided there is no air, bubbles or otherwise, then the ultra sound signal from the transducers will penetrate the 'glue' and hull without hindrance and return with its echo. I had so many air bubbles form at the transom when on the plane that when I had it mounted there, it lost its signal all together. Now, with the thru the hull placing, I do sometimes still loose the pretty little picture of the sea-bed and the little fish shapes, but it does continue to return a depth. If it's bonded like that, then I don't see why any water is needed in the sump as it won’t even get to go between transducer and hull. Other than perhaps to keep the transducer cool?

Interesting that you used silicon sealant, Dave. As you say, the instructions say it’s a no-no. Any 'glue' you use should be solid and rigid to allow the signal to pass. The wobbliness of silicon sealant should attenuate the signal. Having said that, if your only using a thin sliver between transducer and hull, (i.e. push hard) and then pack around the side and top for the 'glue it not to move' factor, then that may well work fine. (Well obviously it does cos you've done it!) I wish now I hadn't read the instructions and done that myself. Much easier to remove!

Anyway, if 'jelly-like' substances don't let ultrasound through, how come they stick it on pregnant women’s stomachs in the maternity ward? Perhaps our resident baby expert, John Kennet would like to comment on that one? ;)

(PS. Dave, Thanks for all the private info on your boats)

The Airmar link I posted, is the What's New page for Airmar. The unit of interest to me is the "new adjustable in hull transducer" which bonds to the inside of the hull and rotates to the particular deadrise angle. The transducer is instantly removable from the rotating housing which is handy for storage. I think this leaves one with more options than a permanently bonded transducer. In fact this unit would not need to be in the aft sump where it could be impacted by other equipment or someone's foot. It could be hidden anywhere in the aft portion of the boat.

Again, the link is:
http://www.airmar.com/whatsnew/f_whatsnew.htm


NR