Well I ordered it and it is now here and contrary to the diagram the gap between the saddle and the clamps with the clamps wound right out is in fact almost exactly 60mm so I am hoping it will fit without further modifications ... boat turns up in 3 weeks so I will soon know
Only slight issue I had is that the kind soul that test ran it in the factory forgot to put the fuel line back on from the tank (I guess they bench run it off an external tank) and thus when I filled up the tank with petrol the first litre ended up filling up the engine cowling, on the floor and over my shoes
after that little 'episode' and cleaning it all out with compressed air so it didn't explode, it seems to run ok in a drum of water, though I haven't had it on a boat yet, hope to try it on the SIB this weekend.
Meanwhile another question - I read somewhere that the baby Mercs are actually made by Twatsoo - is this correct? They certainly look the same in a picture, the specs are identical, and I know this sort of badge engineering goes on as my old Johnson aux was a white Suzuki.