4 MW at 35 deg C would be ideal for 3500-4000 ton class ships. Efficiency of >30% ? It is not mentioned if they want a reversible engine or not. If it is a reversible engine, >30% efficiency in the 1st attempt might be difficult.
BHEL has been making some very powerful gas turbines for a while now. But those turbines are built for electrical power generation not for marine propulsion. Those turbines cannot be directly retrofitted for marine propulsion role. They would have to undergo a significant weight reduction. BHEL's partnership with Bharat Forge might help with the weight reduction.