Looks like a Vetus Uniflex as here vetus.com/en/stern-gear-systems/flexible-couplings/sprzeglo-uniflex-16-8171.html You can download the instructions from that link.
If I remember correctly, Centaflex recommended that a special grease should be used on the conical faces.Thanks all.
It's a challenge to put back together. The clamping cone and its seat are stepped. So while the coupling is only a few inches think the effective cone length must be at least 12 inches. It needs to be torqued to 79NM, which you have to do repeatedly as the cone settles in the seat. You need a long lever to apply 79NM and there ain't much room in the engine room to do that. ....took me over an hour and a bit of boat yoga to fit 6 bolts!