depth transducer

[Guest]

I want to replace my out-dated Navico System200 Depth Sounder and Speed Log. I'm trying to avoid cutting
another hole in the bottom of my Summer Twins catamaran. The Log impellor is "through the hull" but the
depth transducer is epoxied on the inside of the hull. I would like to fix the new transducer the same way but
need to know the pro's and con's of doing this. Will it work properly? ( the old one hasn't since I bought the
boat).
All the salesmen I spoke to at the boat show insisted their products should be fitted through the hull,
although I never managed to get to all the manufacturers.

 

[Guest]

You can fit the new transducer inside the hull and "fire" it throught it. There should be few problems providing you make sure there is absolutely no air bubbles between the transducer head and the hull. This is normally done by filling the tube with Castor oil
Pro's = no hole in hull
Cons = some transducers are apt to miss read temporarily, with the display suddenly reading either to much depth or not enough, especially if your in shallow water and moving at 3-4 knots+, but it's only very short time before display comes back to normal.

 

[ccscott49]

Why is everybody so paranoid about boring a hole for an echo sounder transducer, its a small hole, maybe it does need some packing to get it pointing vertical, but thats all there is to it, as long as the outside is protected by a teardrop shaped pad, whats the problem! I have never in 30 years of boating, seen one sheared off, I'm sure other people have, just to prove me wrong, but a little tapered plug tied to the transducer, and there is your safety. I can see the sense of no big holes and seacocks which can fail etc. But a transducer?

 

[colin_jones]

I have an 'in hull' Lowrance fishfinder txducer. We just stuck it on a blob of silicone, but checked that there was absolutely no air beneath the txducer surface, nor the silicone. It will not work on a sandwich construction hull becauase of the integral air bubbles Ours has worked there for a number of years. It is not quite as sensitive as our 'thru hull' txducer, but is very practical.

Alternatively, ask about a triducer, which is a bronze txducer (normally fitted on a faring block of about 2" to keep it clear of hull 'skin effect). This device might go through your existing hole and will measure speed, depth and water temperature.

 

[vyv_cox]

Fully agree. My experience of internally mounted transducers is not good, their readings are never fully satisfactory due to lag and intermittent loss of signal. Having a bath of oil inside the boat is somewhat risky and on a previous boat I have twice had mine knocked off by a stowed object, releasing castor oil inside the locker (and stopping it working, of course).

Conversely, I have fitted through-hull transducers to each of the three boats that I have owned, without the slightest problem. Performance of the unit improved noticeably in each case. I replaced the older unit in my current boat and I guess it was the original installation, 12 years old and no leaks. The unit I installed then has been in for 3 years, again, not a moment's problem.

I have some difficulty in imagining any failure that could lead to a leak. Water pressure is normally only 12 - 24 inches head, i.e. very low indeed. The unit is robust and quite difficult to break. Even without sealant it will be almost leak tight if installed correctly, and with a good sealant is virtually bomb proof. I can vouchsafe that they are very difficult to remove.

 

[quaelgeist2]

Happy user of an in-hull transducer (first for Seafarer, now moved to NASA) with some oil in the 'cup' underneath it.
No problems whatsoever. Pro : Peace of mind from avoiding yeat another hole...
After curing my hole-phobia and mounting a through-hull pedal wheel replacing a never satisfactory trailing log from AR, I may reconsider my preference for in-hull
;-)
chris

 

[duncan]

I am with Colin - stick it inside works fine as long as (i) no air packets and ideally epoxy not silicone etc. (although mine was fine with silicone) and (ii) it is spowerful/sensitive enough as the thickness of the hull will degrade the signal. Common problem with 'older models' is a combination of lower power unit / reduced voltage through conector corrosion resulting in a v.weak signal.
A Lowrance 'skimmer' 'ducer has worked fine at up to 50 knots like this -and I have just fitted a new 15MX unit and 'ducer the same way. So it might not show all the sand eels in the shoal..........

 

[ccscott49]

Just as an aside, us with wooden hulls, mine 2.3" thick are stuck with through hull anyway!