I see that you have not used the silly reversing gear quadrant linkage that Stuarts suggest, full of threaded unions which are a pain to make and align. I've not actually used the marine flywheel on my D10 setup, relying on the 5 inch prop to give the engine turning momentum.
I've just come back from exhibiting at the Guildford Model Engineering Society steam rally (very hot day). There is a good comparison of using D10 engines, me with the flash (monotube) boiler and a chap (Chris) with a 82lb displacement tug with the D10 and his personally designed and constructed conventional boiler (both immaculate in their execution).
Sadly, we both had teething problems. My boat dropped its shear pin (at least it didn't shear!) from the engine to prop shaft coupling, probably due to the violent changes in engine rotation whilst navigating in the small demonstration pool, and Chris lost the servo to steam reg valve coupling due to the grub screw coming loose.
Still, we are both there tomorrow and, hopefully, will give a good demo of both types of operation.
As you say, it would be boring without these "challenges".