Unfortunately the inscription at the bottom of the first sketch on this page, which looks like ‘Ilonsay’, does not help to identify the location as there is no such place. The view was made from a height near the shore of a loch which he look across. The far shore is surrounded by hills and there are several vessels at the right of the loch. During his exploration of the Scottish lochs Turner took a steamboat trip up Loch Lomond and on Lochs Long and Goil, and coached or walked along the shores of Lochs Arklet and Katrine (see Tour of Scotland for Scott’s Poetical Works Tour Introduction). David Wallace-Hadrill has suggested that the most likely locations are either Loch Lomond or Loch Katrine.1
The other sketch on the page, made with the book inverted, is of mountains by the side of a loch. There is nothing specific enough to narrow down its location.
David Wallace-Hadrill and Janet Carolan, ‘CCLXX “Stirling” Checklist’’, [circa 1991], Tate catalogue files.