I took the advice from a previous thread, and silicon'ed the transducer into the bilge well at near the bilge pump.
I built up a dam from modelling clay, and filled it with a good thick layer, and made sure the ransducer was horizontal as possible, and no air bubbles were in the silicon, and left it to set.
If it was not right I could have redone it, but it was fine.
It gives a good reading, even at near WOT.
When I got the Rib the transducer was fixed half way up the transom, so over 5 knots it didnt work................