Furthermore, if your compass actually points to 336°, as compared to the alignment of another compass held away from the boat (and not over concrete where reinforcing steel will give a false reading) then the angle of deviation is 4° W of MN.
Ukudlula apho ukuba ikhampasi yakho ikhomba ku 336° xa ithelekiswa nenye ikhampasi ebanjiweyo kude kunesikhephe (kungekho kuqina kukhulu xa kuqinisekiswa ukuba intsimbi izakunika imposiso yesifundo) ke i-engile yokuphambuka ingu 4° W we MN.