I concur with Doc. I have a 265 Express and the first year I had the boat (2010), I installed a P79 in hull tducer, connected to a Raymarine c120W. Worked ok to about 15-20 mph but then lost the bottom. Resolution on wrecks and shoals was lacking compared to my prior set up on my Black Watch, which used a through-hull with fairing block. I was dissatisfied so this past year I installed a P60-20 through hull on the opposite side of the keel from the P79. Disconnected the P79 cable from the Raymarine unit, of course. The improvement was very significant and it would give a bottom tracing (to 120 ft) at 50 mph. Resolution improved dramatically. I did not want transom mount - worried about taking it out if I hit something, which happened on an old boat of mine. Got temp readout as well. The P60 is easy to install- no fairing blocks and custom cutting- drill the hole, apply 4200, tighten most of the way, re-tighten the following day and you're done. As I recall, the cost was not bad as well. Hope this helps.