Hi,
His records for his MN service will depend on when he left the service. He could have joined circa the mid 1920's but if he left prior to 1941 then you need to check the Fourth Register of Seamen. If he served into the war then his records or at least those from January 1941 will be held in the Fifth Register of Seamen. The Fifth Register continued until 1972.
So do you know when he left sea service?
Stevedore time will not be recorded in those records.
I am not at home at the moment and a cursory check finds nothing but I will do a proper check when I can and let you know. Also, do you know where he was born?
Regards
Hugh