When you say "inner unit" it means to me that your transducer is meant to be
removeable by simply unscrewing the cap and pulling it out. Such
installations also have a blank plug to be installed in place of the
transducer; it has an identical screw cap. You should have one of these. It
enables you to leave the transducer out when the boat's not being used to
minimize fouling and to enable easy cleaning. You can also conveniently
test the removed transducer by spinning the paddle wheel manually or with a
blower.

There should be a closure flap in the hollow thru-hull tube that will
partially close the opening when the transducer is withdrawn and keep out
most of the water -- if it's working.. A sponge is all that's usually needed
to wipe up the leaks. No need to be in a big rush -- just keep the blank
plug handy.

If by some chance yours is not designed to be easily removed, as described
above, and is a permanent installation, in water removal/replacement is not
advisable. Don't even think about it unless assisted by someone who knows
all the tricks and has done many of these underwater replacements.

Len

--
Eliminate "ns" for email address.
"Gerald Atkin" wrote in message
.. .
Is there any particular trick to changing a speed transducer while in the
water other than being very quick. I need to replace the inner unit and
while I can haul the boat I felt it might be worth a try to do it while in
the water. Is the force of the water such that it might impair the
insertion of the new unit? Any suggestions.

Jerry