Cronk Moar is in the Glen Roy area of North West Lonan (SC 413 836). Nearby is "Thalloorallagh" but these are well inside Lonan. From the statememt in the will perhaps a search of an old map on the boundary between Lonan and Onchan, especially from the Half-way House to Creg-ny Baa, might produce similar names? (enter "Old-maps" in google, go to "Maps" section and enter "Laxey" to get a map of Lonan ca 1870)
The John Cowley you were pursuing may possibly have married Charlotte Kneale als Quayle on 15th Dec 1853 Santon. She was b. 1826 d/o William Quayle and Elizabeth Quinney (IGI). Charlotte had an illegitimate child Thomas in 1843. She married Thomas Kneale in 1846 at Andreas, they had a daughter Margaret, then Thomas died in 1847. Charlotte was in Dgls in 1851 with her parents & children in Strand Street. Thomas was given as Thomas Lace.
1861C: RG_09_4417_48b; Dgls_4_90: 4, James St: John Cowley, Head, M, 30, Labr, Marown; Charlotte Cowley, Wife, M, 32, Ballaugh; Thomas, Son, U, 17, Boatman, Bride; Wm, Son, 7, Dgls; Alfred, Son, 5, Dgls, Eliz, Daur, [0], Dgls.
1871C JC & family not found.
1881C: RG_11_5603_12a_p11; 13 St Barnabas Sq Dgls: John Cowley, Head, Widower, 49, Quarrier, Marown; Elizabeth Daur, S, 20, Dgls; Henry, Son, 14, Dgls.
Charlotte Cowley, 53yrs, was buried Braddan in 1879.
Mary Elizabeth Cowley married John Quine 9th Feb 1882 Dgls (BL records).
1891C: RG_12_4688_126b; Dgls_16_50; 54 Strand Street Dgls: John Quine, Head, M, 35, Boot & shoemaker, Onchan; Mary Quine, Wife, M, 38, Dgls; William J, Son, 6; Elizabeth, Daur, 4; Thomas, Son, 3; Emily, Daur, 3mo; John Cowley, Father-in-Law, Widower, 61, Quarries labourer, Marown; Christian Kneale, Servt, 14, Gen Servt, Onchan.
Braddan Burials; John Cowley, 67yrs, 03APR1900.
These are not confirmed, of course, but may be worth further checks?
JohnL