I had a fishfinder that I located slightly offset (flatter surface) behind
the keel. I puttied a PVC tube just larger than the transducer onto the
surface, filled it with mineral oil, then put the ducer in there to test it.
When I was satisfied it worked, I glassed in the PVC, put the ducer back in,
then refilled the tube with oil. I also put a cap on the top of the tube to
keep the oil from sloshing out. Worked fine, even with the slight angle. It
wasn't accurate for over about 50 foot depth, but who cares at that point.
No extra holes in the boat is my preference.

--
"j" ganz @@
www.sailnow.com

"Don White" wrote in message
...
Luc wrote:
does a fish finder use the same transducer as a simple depth sounder?
It would be handy to be able to use the same transducer, since changing
them out is a chore, and involves hauling out the boat.



The fish finders I see use a 'transom mounted' transducer.
I don't think this is a good spot on a sailboat like mine...with the
rudder hung on pintle & gudgeon, and the outboard mounted on it's bracket.
I'd want the in-hull type I could mount in my cabin just forward of the
keel box. (cut down on turbulence)