The Tomono Iron Works of Tokyo built a water-cooled, vertical-six engine with 90 hp at 1,200 rpm.

- It was designed and built by Tomono Naoji.

From Appendix 7: The Tomono Iron Works of Tokyo attempted to build flying boats and their engines. The Tamai 2 Seaplane featured the Tomono water-cooled, straight-six engine with 90 hp.

“The 90 HP Tomono on Hydro” (PeT-fmr)"