See Simrad in Archives.
Go to the Forum Archives and search on "Simrad WP30" and "exact phrase". The Related Link is one example of several.You would always install a below deck unit if cost was of no consequence. But since it usually is on an older boat then a wheel unit will do fine. My Simrad has never failed me on my H37C.Link to WP30 pics:http://www.sailboatowners.com/upload/display.tpl?folder=73188464571&fno=17