You can join merchant navy after B.Tech in ECE..
Generally,one have to the B.Sc in nautical science or 4-year engineering in marine engg to get into the merchant navy..
Now as an ECE engineer, you have to complete the one year post graduate course in marine engineering to get into merchant navy..
There are four Govt institutes like: MERI,Mumbai, MERI,Kolkata, T.S.Chanakya Academy,Pune etc giving pre-sea and post-sea trainings to the candidates and there are other private colleges too..
After completing this course,you can join as deck cadet officer