If you don't want a new thru hull the oil bath method works great.

+1 for oil bath, 30 years ago tested / use it first time / with rotating light depth sounder , works well

cazou34 said..
If you don't want a new thru hull the oil bath method works great.

so, take a small plastic sandwich box, put the external type of transducer inside, silicone it to he hull, fill it with oil?

Seebreazy dont forget mounting the transducer as far forward as you can is advantageous. You get a small number of seconds advanced warning of the bottom coming up before it might hit the keel if you do that. A bit like having someone standing on the bow testing the depth with a big stick.

Our depth transducer is at the bow screwed down in a thin layer of Vaseline to get rid of the air between it and the 25mm hull. Works great. The vaso doesnt run everywhere and you can still replace the transducer if need be.

Seebreasy73 said..

SandS said..
an old garmin s half a tube of silicon to bed the transducer down inside the hull . looking through at least 15 mm of solid fiberglass .

No problem !

do you mean the type that usually mounted on the transom?

yeah i think thats what it was meant to do .... nearly 7 years ago cant remember ..... still works a treat ...........

Bought inhull/transom from States few months ago. They sent through hull. Took a couple of months to get the inhull and they asked I return the through hull at my cost! So I have both . Can a through hull transducer work as an in hull