Sea Panther core plugs

[Dytiscus Rubra]

Hello all,
I wondered if anyone had any experience of the core plugs fitted to the two models of Sea Panther. I am all ready stocked up and waiting at the starting line to set off for the Solent rally when after giving her a last bomb around Walton on the Naze Backwaters I notice a water leak ! It looked quite serious as it was leaking from the gearbox bell housing and so I returned to Coventry on Monday to study the manual. It appears that there is a core plug at the rear of the engine so it is gearbox out flywheel off to replace it .... Great. I called Stephenson marine who confirmed its existance and as a gesture of sympathy put one in the post to me FOC. Arrived today great service as usual. Now for the complication.
I have a spare Mk 2 engine so I stripped it down giving me a head start when I do surgery on Dytiscus R. I found that where the Mk 1 manual shows the said core plug, on the Mk 2 there is a solid lump of steel looking nothing like a core plug and so after this tiresome story I beg the question if anyone has any knowledge of the Mk 2 Did they not bother with the core plug ? Help.
Prior to my mercy call to Stephenson tomorrow !!

All the best,
Colin.