Thanks Paul for the suggestions. It looks similar to a type 13 but Vetus indicate this is only suitable for up to 45 HP and the 331 is 75HP. The type 16 appears very different on the vetus website. The whole question arose from a minor vibration in the propeller shaft and the suggestion that the rubber bushes in the coupling might be worn. All the advice I have is that this is unlikely and much more likely to be either a worn cutlass bearing and/or P bracket bearing. The boat comes out of the water next month so we’ll be able to investigate further.