The valve is not the issue with the engine

I work on the Atlantic and spend much of my life at sea, I run a boat business, my business partner is a marine engineer and RNLI mechanic, we've both served on lifeboats, we know a thing or two.

There is zero, literally zero chance that engine runs for two hours with the seacock (what that valve is called) closed. At best it would run for 5, if you're lucky 10 minutes before it will catastrophically fail.

I can't believe they wouldn't know that already from the most basic research about marine engines.