If ammonia fuel happens at all for merchant vessels then for efficiency reasons it will be run through reciprocating engines, not turbines.
https://www.wartsila.com/marine/products/engines-and-generat...
But I have my doubts. There's still no economically viable way to produce "green" ammonia at scale. It's hazardous to handle and less energy dense than liquid hydrocarbons.
Which is why we won't be burning ammonia and shouldn't even try.
We already have an entire, scaled up industry of producing artificial fuel in a non-petrochemical route: It's where the ethanol in your gas tank comes from.
Farming will be easier to electrify than shipping, or it might not even need to be, and then we will have ample supply (at least here in the US) of energy dense fuels produced through non-petrochemical needs
Growing corn to turn into ethanol to burn isn't like, a carbon negative process right now, but it's also viable today to provide energy dense fuels in a sustainable way to feed our needs like long term storage, compactness, emergencies, and things like planes which won't work with batteries very well.
We already supply enough artificial hydrocarbon fuel through that process to make up 10% of all gasoline burned. As american cars electrify, the corn farmers are going to lose their shit about this subsidy being reduced, so we should just turn it around and have them commit to a larger artificial fuel industry. Our corn growing is already basically a fully socialized industry, let's just lean into it more. Put less corn syrup into random foods like burger buns and put more of it into vats to get energy dense fuel.
It's (technically, barely) an energy positive process, is extremely scalable, is fairly old "tech" such that it won't be owned by one company or country, and the hardest part will be replacing the petrochemical fertilizer.
Oh, ethanol is a more energy dense fuel too.