In whose portion was Tapu'ach?
Rashi (17:8): Tapu'ach was of Efrayim, but Eretz Tapu'ach (the villages and their Chatzeros; Malbim - north of it) was of Menasheh.
What is the meaning of "Yelech ha'Gevul Yamah"?
Bi'ur ha'Gra: From Tapu'ach, a strip extended from Efrayim to the sea, south of Menasheh.
Did Nachal Kanah belong to Efrayim?
Malbim: South of it was of Efrayim, including Gezer (verse 10); north of it was of Menasheh.