WW2 aluminium speedboat identification

I wonder if the number of the hull was derived from a similar system to one that I am acquainted with,in which the first digit(s) refer to the builder's type reference and then the hull's number in that type.Possibly indicating that this was the 10th variety of hull that the company had produced and that this was the 167th of the type to be built.

A six cylinder engine in a boat so small must have given a very exciting ride.It also makes a kind of sense for a six cylinder horizontally opposed engine to be selected as it would only stand three cylinders high.It might aid your engine research to get some pictures of the engine mounting flange as the bolt pattern would be helpful in confirming the type of engine.It could have been linked to Dr Ferdinand Porsche's preference for horizontally opposed engines and he had a role in the development of the Mercedes 170H.

 

In the Wiki link about the M15 engine, it says it is an inline 6, which is probably too long/high to live under the deck here. But MB did produce a variety of engines pre-war, so there might be another up their sleeve.

 

Thanks guys!
Mercedes is still searching about the engine (i asked if they have evidence of some commercial stuff between Daimler/Mercedes and S.A.R. in mid 30s). This also could be mounted as not new (prototype?).
In attachment a pic of one of the boat from Cantieri Taroni Stresa, which were used to mount Alfa or Ford engines vertically.
@WetFeet one of the last Porsche boat engines (car engine transformed) is shown in Museo Della Barca Lariana, pic in attachment too!
!

 

This week is running really fast.
Yesterday i found and collect more information on S.A.R.A // Società Automobili Roma Anonima, that has been founded in 1905 and operates until 1915, when the King government took their plant to made Reale Fabbrica d'Armi (Royal gun factory) that still standing in Rome.
It was a big company, the shares value of full capital was 3mln Lire in 1905, about 13Mln€ actualized.

Most incredible, a local historian found a person who have seen this thing operating (he is the 92 years old, son of one of the Hydroplanes pilots) that clearly remebers the soldiers runnint from hydroplanes pier to local bay which was hosting actual war powerboats (MAS).
The historian also said that is a common thing if some modification has been done on a 1910s powerboat during ww2 (at that time Sardinia was basically a war testing field, he says, as malaria was everywere and nobody was around if not on a mission).

If i'm lucky enough, i will have a personal meeting with this person (who is still very lucid about ww2 events) in the next weeks.

In attachment: 5 shares of SARA

 

I did a search for views of the engine from the Mercedes 170 H and it had a four cylinder engine,perhaps more relevant,the image I am attempting to include shows a circular group of fastenings holding the rear cover over the crankshaft.The hull of this boat seems to have a circular group of fastenings on a flange,just above the bottom.

 

Thanks! This is really helpful. Our last research talks about an original engine by Isotta-Fraschini (waiting for their reply) then a modification to Daimler/Mercedes by Axis Soldiers!

 

Also some news from local book collectors is this boat should be identified as BSRA - Barchino Servizi Regia Aeronautica (Royal Airforce Service Boat), used to carry the pilots from their residence (Casa Gioiosa, Porto Conte - Alghero) to the Seaplanes pier, on the other side of the same bay.
They're still searching for some pics on a specific Sardinian book about ww2 events.

 

Thanks for sharing as its brilliant design and an incredible history.