There is no reason to doubt that Invincible Stovers were built here. The following article gives some idea of Invincible's capability. From Australian Motor Boat & Yachting Monthly, Sept 1930:
Invincible Motors, Limited, are celebrating their 25th anniversary during September. It was on September 1, 1906, that Mort's Dock and Engineering Co Ltd, founded their "Invincible Motor Department" at Woolwich Dock, on the Parramatta River.
Due to the foresight of the late JP Franki, general manager of Mort's Dock and Engineering Co, Ltd, the new industry was put on a sound basis at the start by substantial financial allowances and the use of the enormous plant of this large firm.
So to speak, the Invincible Industry may have been started with the lowest possible protection (the Customs duty then being only 20 per cent, as against over, 80 per cent to-day); but otherwise this new industry was born with a golden spoon in its mouth. The resources of Mort's Dock, with its large foundries, forges, and machine shops were at the motor department's disposal from the start. No wonder that within six months a complete line of marine engines from 2-1/2 hp to 80 hp, and comprising 20 different models had been designed, made, and catalogued.
By the middle of 1907 about 150 hands were directly or indirectly employed at the great works, solely on motor work. At that time Invincible marine engines were 100 per cent Australian; even the carburettors were entirely made at Woolwich.
The first manager resigned in 1909, and then the motor department was formed into a separate limited liability company, with Mr KF Boehm as managing director, a position which he has now occupied for 21 years.
The Chief Engineer of Invincible Motors Ltd, Mr WH Rowe, who joined the company In 1909, is still in the same position, and so is Mr EJ Dempsey, one of the original directors.
Eric