Hi Joe, I have older SR Mariner analog instruments in my M17. The knotmeter is driven by the paddlewheel thus does not need battery power. The depth sounder does work, but, in my opinion, rather poorly. False or no readings are common, and, it seems to not function when you need it the most. I think both are useful, and I would always wish that info helming my boat. The new Navman pieces recently install on the M23 are fabulous, they work like a charm. Nothing like technology. PS, there were already holes in my hull for the transducers, so the question on whether to drill or not was not an issue. Later, Bones ____________________________________________________________ Live the good life! Click now for great retirement planning assistance! http://thirdpartyoffers.juno.com/TGL2141/fc/PnY6rw1hgiHMNiLiSV8DaJNOsMyJueA8...