Oh! well that puts a light on all this then,if you sat he was still active (At Sea) in the 70's that means then that there will be no Records of him kept,as they stopped Keeping Records after 1972 again for reasons unknown,they again restarted a few Years later!
Southampton however may hold records of his in that case!
This separate Register of Seamen extracted from Crew Lists was abandoned in 1857, due to the problems of maintaining registers based on Crew Lists. Following three previous registration systems, a new Central Index Register (fourth register) was introduced in 1913 which survived until 1941 followed in 1942 by a new Central Register of Seamen (fifth register) which lasted up to 1972. Unfortunately no records exist from 1973 to 1999 as legislation was not required to keep records of individual seamen. From 1999 onwards the Registry of Shipping and Seamen in Cardiff holds records of service extracted from the ships official logbooks and crew agreements.Series IV/Central Index Register
(1913-1941. Unfortunately entries between 1913 and 1918 were destroyed in 1969. The originals are held at Southampton Archives with copies available at TNA in series BT 364 as a combined index of the CR1, CR2 and CR10 cards)Series V/Central Register of Seamen
(1942-1972, TNA series BT 382)
I would therefore write to the Archives in Southampton and ask the Question concerning this issue ,they will be able to tell you if Records for him do exist!
Cheers and Best of Luck.