Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Please do not think I'm being critical in a casual manor, but since you are asking for input, I will give a critic of what I see.

That boiler looks to me to be just a little bit undersize for a Stuart #9, as it appears that the cylinder is a significant fraction of the boiler's diameter, and that boiler isn't any too much longer than the cylinder either. That #9 is going to eat through one heck of a lot of steam with each stroke even if not under any load!

It appears that the inside of the cylinder is showing rather heavy machining marks from being bored, and I would think that a careful honing job would be very beneficial there.

Need I mention that all of that uninsulated steam line is a real efficiency killer, while at the same time having a governor in line might be cause of a further restriction unless really properly built and adjusted (ie: fully open) at zero throw-out?!?!

Possibly the exhaust is overly restricted using smallish piping from the cylinder's exhaust, through the oil separator and into the condenser/water tank and onto the exhaust vent from there.

I cannot judge the efficiency of the fire heating the boiler, but to get all you can out of that unit, it will need the most efficient heating you can manage.