Here is a nice 1914 article about the detachable motor
that you can read from a scan.

Click on the the photo to go to the full sized page...OR...read a transcript below.

This is all I have found so far. It sounds like it was real...I wonder what went wrong that either stopped its production, or buried it so thoroughly that it does not surface in a persistent Google book search.

Items of Interest -

SUCH are the possibilities of an outboard engine for light boat work that one cannot but feel amazement at the manner in which this line has been neglected hitherto by manufacturers in this country, although during the last four or five years the British market has been exploited with success by the salesmen of foreign products. This latter circumstance has led to a recognition of the advantages to be derived from this mode of boat propulsion, and, the necessary educational and pioneering work having been performed and the outboard engine having demonstrated its popularity, at least one British firm has decided fo enter this promising market.

We had recently the pleasure of being present at a demonstration on the River Lea, at Broxbourne, Herts., of the 2-3 h.p. Spartan outboard engine, the trials of which were conducted under the auspices of Messrs. Goodrich, Hamlyn and Arnaud, of Arundel Street, Strand, W.C., who are the selling agents for this engine, the construction of which has been undertaken by the Spartan Engine Co., of Brandon, Suffolk.

It is, of course, essential that the outboard engine should be capable of easy attachment or dismantling; in the case of the Spartan engine there were provided two cast iron clamps, of a shape similar to that of the type commonly employed in fitting shops, dependent from, and integral with, the body of the engine. To attach the engine to a boat, therefore, it is necessary only to slip the engine on to the transom in such a way that, when the screws are tightened, these clamps will grip firmly the back of the boat—an operation that may be effected easily in three or four minutes. It is considered desirable by many to discharge the exhaust under water, and to this end the burnt gases are led through a cast aluminium exhaust pipe to a receiver on the head of the gunmetal exhaust tube, through which they are conducted to an outlet situated beneath the water level and close to the bottom swivel of the rudder; through this outlet the escape of most of the gases takes place, although a small proportion will naturally find its way out through the holes that have been drilled above the water level in the lower part of this pipe— the purpose of these holes being to remove any danger arising from the possibility of water being sucked up through the exhaust pipe. So far as the choice of materials is concerned, while the cylinder and crank case are of cast iron, the propeller and the exhaust and shafting tubes are of gunmetal, the remainder of the parts being of aluminium, except for the sheet iron petrol tank. It is noticeable that there are no white metal bearings in the engine, phosphor bronze being everywhere employed. The engine is of the three-port, two-stroke cycle type, which has been adopted because of the unsuitability for a detachable motor of the valves and gearing incidental to the four-stroke cycle. Power is transmitted from the crankshaft to the propeller through a bevel gear, the driving wheel of which is carried on the lower end of the crankshaft extension; on the boss of the driving bevel wheel is formed a cam that is made to actuate a water pump of the plunger type, the pump being accommodated in an aluminium casting beneath the water level and forcing water to the jacket by means of flexible metallic tubing having indiarubber connections. Through a similar flexible tube the cooling water is discharged from the jacket to an outlet beneath the water level. «

An upward extension of the driving shaft carries the flywheel, which is utilized for starting the engine. There is no protruding handle on this flywheel, the designers being of opinion that such a provision is dangerous, especially when the engine is in the hands of an amateur or novice; actuated by a cam formation on a boss beneath the flywheel is a contact maker of the wiper type, there being provided a handle by which the spark may be retarded sufficiently to obtain a satisfactory timing for reverse running. The ignition current is furnished from dry storage batteries, but a magneto may be supplied instead, if the customer should prefer it. Behind the flywheel is carried a petrol tank of 5 to S5 pints capacity, this quantity of fuel being sufficient for about five hours running of the engine.

The rudder is carried on a separate shaft from that to which the propeller is fixed, and, unlike some other outboard engines, the steering may be accomplished from the forward end of the boat by means of ropes attached to a crosspiece that is made to grip the rudder shaft by means of a set screw. In fixing the engine to the boat, considerable latitude is possible in the matter of determining the exact position in which the engine shall lie, and either downward or outward variation of its position is rendered possible by the provision of links which, depending from a fixed pivot, arc attached to the driving shaft casing in such a way that this may be swivveled into various positions by the simple process of loosening set screws.

During the demonstration trials at Broxbourne the Spartan engine was fitted to a 19ft. double-oared skiff of a type usually to be seen in pleasure boat yards on rivers and lakes in this country. Naturally, the engine presented but little difficulty of starting, and appeared to accomplish its work quite easily, propelling the boat at a speed of some eight miles per hour, the petrol tank being first filled with a mixture, in suitable proportions, of petrol and lubricating oils. After a series of successful runs had been accomplished, we could not but be impressed with the fact that engines of this type, although their market undoubtedly will be found mainly in the sphere of pleasure work on rivers, should find an extensive application to harbour and river work of a utilitarian nature,' and should especially be suitable for the purpose of the officials of shipping companies and others who wish to make frequent visits to ships that are lying in a harbour, or that in any other way are not moored to a quay.