If the impeller is slightly off or theres a little eel grass or a little nettle. Then, if you generator goes off, I wouldn't find it so convenient.

You also need a delay on that circuit (or you'll be in an old FORTRAN IV "DO Loop" -- a/k/a "Do Over", circular failure.)

I think that unless you're not on the boat, it might make sense. Otherwise, I believe it gives you time to do something.

In the case of the engine at (say) 2,800 RPM into a tough seaway, you don't have a lot of time if you loose a belt or impeller. I wouldn't want the engine to just "cut-off", but I'd want a notice that is pretty "hair trigger".