Hi Sarah , hi Trev,
We have an older Maramu (#79) and installed a holding tank in the forward head - the boat does not need go come out of the water for this work , as it uses the same sea cock with a Y valve fitting - all the other necessary holes ( breather and pump out ) are above water .
I can send you some images if you want.
They are great boats for cruising and voyaging .
All the best
Andy and Fifi
Sent from my iPhone