In Hull or Transom Mount Transducer?

[mm289]

Originally Posted by Pikey Dave

Just sticking my pedantic 2 penneth in. "Through hull" & "in hull" are very different beasts. Through hull is the case in point here, I.e sticking the transducer inside the hull & it "sees" through the hull. "In hull" however, involves drilling a hole in the hull & mounting the transducer on the outside of the hull with the cable passing through the aforementioned hole. These are common on yachts & displacement hulls.
I'll get me coat.....

No probs Dave, but I think you have it the wrong way round , from Raymarines website:
"In-hull (a.k.a. shoot-through) transducers are epoxied directly to the inside of the hull." "Through-hull transducers are mounted through a hole drilled in the bottom of the boat and protrude directly into the water."

I know it sounds counter-intuitive, thats what I thought at first so had to research it

To warm to wear a coat anyway

Cheers,

Paul.

[Pikey Dave]

I stand corrected

[Orwell boy]

Out of interest i went out today ,i had potted my transom mount in an old wideish yoghurt pot in silicone sealant (which never really set more than 90% ) so i could move it around to find the best signal ,bit of a mess really ,and didnt find much signl either as i had wrongly assumed the potted sensor face was where the signal was fired from , so to cut a long story short ,removed the silicone ,shoved the sesor in a ziplok poly bag full of water and put it next to the bilge pump , perfect signal as fast as you like
so was transom mout 6 pin sensor in plastic bag full of water placed in the hull ,next to the bilge pump

[mm289]

Just to update this, I have been using the Garmin transducer mounted to the outer edge of the transom on the Frib for the last few trips.


At the moment rather than permanently mount it it is held on with Sikaflex 291 so if it doesn't work I can peel it off.


I followed the general advice on mounting transducers, trying to avoid strakes on the hull and lining the bottom of the TD up with the bottom edge of the hull.


You can see where it is mounted in the pic, basically between the wheel mount and the tube. Ideally I would have had it inside the wheel mount but that gets pretty close to the engine. The advantage to that would be it is deeper in the water - one of the challenges with having it where it is is that to enable it to read effectively on plane I have it tilted back slightly, but this means when at anchor it almost comes out of the water and doesn't read at all.


That said, it seems to be working quite well and will hold bottom as about 12-13kn. In Scotland this weekend so it will be interesting to see how it performs in deeper water and at higher speed.


At the end of a session I just fold it back in line with the transom and am careful not to rest the boat on this end when folded.


Cheers,


Paul.


PS apologies for the upside down image, I have changed the orientation of the original and re-uploaded 3 times now but it still shows upside down

[Fenlander]

I've been fiddling with our transducer height for each run this year. Since doing the 45mm transom lift... then buying the 15hp Yamaha plus getting the best prop and trim position... I'd realised the transducer was the only real remaining source of splash.

Mines on a timber leg and I've dropped the transducer as low on the leg as I can and also lifted the leg on the transom each time until I found the point where splash was minimal and 90% of the time on the plane the depth read OK.

You can see broadly I've ended up with a similar transducer to transom/hull relationship as yours. Of course the Aerotec water flow is naturally more erratic which does cause that very occasional loss of signal.