I have refurbished an Enfield leg and am fitting a new zinc ring into the skeg and behind the prop, it comes with two grub screws but I dont know what these are used for as there is nowhere to secure them to.
Do you have the correct ring? On Volvo Penta legs the two stainless steel screws are for just that purpose to secure the ring behind the ptop. Just a thought, were two screws fitted originally and have now been sheered off? Sorfry that I cannot be of any more help.
I have the correct zinc ring and it is the same as the one removed but even the grub screws in the old one never clamped anything. I will ask silette Monday.
The grub screws just sit against the housing to secure it, it's a crap design! Chuck the anode in the bin as you'll either overtighten and distort the housing making it leak or leave it too loose and vibration will make it rattle loose and do no protection whatsoever, put a pear shaped duff type anode on top of the anti-cavitation plate instead.