Aktungbby has got it!
It is a german plane's engine, make and model "Rapp", in German East-Africa. Therefore the typical slouch hats worn by the german "Schutztruppe". The photo is taken in Dar-es-Salaam, where the Rapp engine was being mounted on a "draisine", a railcar being converted to be powered by airscrew, on the german Dar-es-Salaam - Kigoma tracks of the Ostafrikanische Eisenbahngesellschaft ~ East African Railway Corporation. Thus Aktung's "Schienenzeppelin" link 
.
This vehicle did absolve two successful voyages on the tracks from the coast to the Tanganyika lake, and back. Then missing spare parts and fuel becoming scarce, the project was abandoned.
(There is a nice description of the problems railroad builders ran into in Africa from termites eating the sleepers/crossties of the rails, to elephants and giraffes running into telegraph lines and poles, in Stevenson's "Ghosts of Africa", a novel about the fighting in Africa: https://www.amazon.com/Ghosts-Africa.../dp/1629144436.)
The AGO/Pfalz in military service, guarded by german Askaris:
The AGO during the rebuild as a seaplane. Buechner injured with white bandage in the middle:
The AGO as a seaplane, in the Rufiji delta:
The plane was invented by
Gustav Otto, the son of the inventor of the internal combustion engine, Dr. Nikolaus Otto. It was an "AGO Doppeldecker", later also called a "Doppelpfalz".
The first plane was built by the Gustav Otto Flugmaschinenwerke, later renamed to AGO (Aeroplanwerke Gustav Otto), and most machines were then built under licence by the Pfalz Flugzeugwerke.
Pfalz intended to advertise the plane and sent one to Africa, for showing what the plane type was capable of.
The engine used for the plane to be shown on the english-german fair in Dar-es-salaam was a construction from Mr. Rapp and his Rapp Motorenwerke (
https://en.wikipedia.org/wiki/Rapp_Motorenwerke), which was later to become BMW (Bayerische Motorenwerke).
As i already wrote in the 100 years ago thread the pilot and his plane were forbidden to fly from Deutsch-Suedwestafrika to Deutsch-Ostafrika over british territory by british authorities, so Buechner, his wife and the plane were instead shipped around the cape of good hope to German-Eastafrica.
The steamer belonged to the Woermann-Line, first officer was Mr. Krause (friend of my family). When they arrived at Dar-es-Salaam, the ship was unloaded, stuffed with colonial goods and headed back to Germany. It never arrived, but this is another story. After being assaulted by a british boarding party in a neutral harbour, the crew and Mr. Krause punched through Mozambique and its enemy lines and joined the german outpost in the Rufiji delta, where they helped unmounting the SMS Koenigsberg's guns for mobile land-use of Lettow-Vorbeck's Schutztruppe and Askaris.
Pilot Buechner assembled the plane and made a few flights around Dar-es-Salaam, when war broke out. So the fair was canceled and Buechner proposed to Lettow-Vorbeck, the military leader of the german "Schutztruppe", to use the plane for military purposes. Vorbeck agreed, but Buechner was injured and his plane damaged in the first recce mission, by british naval forces.
The plane was then ordered to be rebuilt as a seaplane, using floats instead of a landing gear, to help gathering intelligence in the Rufiji delta, helping the SMS Koenigsberg against the arriving british monitors.
After several successful recconnaissance and "bombing" missions (the plane was not really suited for anything of this kind) it was considered as not repairable. Engine and airscrew was then mounted on a railcar, to be used for pulling goods on the Kigoma railway.
The guns of the SMS Koenigberg were transported via said railway to the Tanganyika lake, where they were intended to be mounted on the german "Graf Goetzen" steamer, for control of the lake. But it was never intended to be used militarily and therefore unsuited, the deck structure being too weak to accomodate the Koenigsberg's guns. So Lettow-Vorbeck mounted the guns on wheels instead, to be used as mobile artillery.
Instead they cut a palm tree, mounted it on the fore deck of the Graf Goetzen, and painted it grey. It was enough to scare away enemies.
The ship also inspired the film "African Queen", where Humphrey Bogart personally sinks the german steamer..
The "Graf" is still underway on the lake today under the name "Liemba".
https://en.wikipedia.org/wiki/MV_Liemba
The english Wiki is partially wrong though, just linked here for english readers.
Thats's it,
in a nutshell 