The 74-year-old retired accountant left his home in Cross Hills, near Keighley, last Monday to 'recce' a route in the Yorkshire Dales and did not return.
Intensive searches have focused on both Wharfedale and Swaledale after his Volvo was located parked in Kettlewell at the end of last week.
A farmer discovered his body this morning (Monday October 25) in the Coverhead area, near Leyburn.
Although his body has not been formally identified, it is believed to be that of Mr McCartney and his family have been informed.
There are no suspicious circumstances and the case will be passed to the coroner.
The RAF, National Police Air Service and several local mountain rescue units joined police in the search.
North Yorkshire Police would like to thank members of the public for their assistance with sharing the appeals to find David.