Caille Rowboat Motor - about rudders...

The detachable rudder was an option. This is the only original one I have or have seen. See this particular 1916, Caille 5-Speed Rowboat Motor.
Note: There have been a small number of reproductions of the original made.

Rudders were seen as necessary by some early outboard owners because a rudder provided steerage when the motor was turned off. They wanted to approach the dock safely (and not make a fool out of themselves).

With Caille's 5 speed motor you didn't need to shut the motor off while docking, you could shift into neutral or reverse....and that is why they didn't sell many detachable rudder options as most folks bought the 5 speed which became available in 1915, the same year the detachable rudder was introduced.

A "semi-detachable" rudder in a slightly different design was also available on Caille made Hiawathas (badge motor for Montgomery Ward).

1913, Caille Skegless Rowboat Motor	1914, Caille Rowboat Motor, #503	#601C	1916, Caille 5-Speed Rowboat Motor with detachable rudder option	Caille Rowboat Motor, # 2419
There are more Caille rowboat motors on the Caille site.
Caille 5-Speed Rowboat Motor with rewind #22995-C	Caille 5-Speed Rowboat Motor with rewind #28969	Caille 5-Speed Rowboat Motor #30568	Liberty Single, #32?16	other optional add-ons