In hull depth transducers.

[Thresher]

15 years ago I bought a cheap fish finder (can't remember the make). I thought that I would be able to place the transducer in a tube of oil in the bilge, I tried different locations and although it worked it degraded the signal so much that it greyed out the screen. I ended up having to hang it off a stick over the transom.
I'm now in the market for another one and don't want to have the same problem.
Has anyone else encountered the same problem? are some fish finders better than others at seeing through the hull and if so what should I be looking for in the specification?
Thanks, Brendan.

 

[MikeCC]

Sheer transducer power can overcome that - the old one may have just been a bit feeble. If you want decent fish finder results rather than just depth, through-hull (ie transducer face in the water) is the best way to go. For features like downscan, it's the only way due to the high frequencies used.
The transducer must be vertical to the water otherwise the return signal will be scattered away. Depending on boat type, fairing blocks or tilted element transducers can be used to achieve this.
In general, they are much better than 15 years ago.