I was able to confirm from Dessalator the the pump for my model (180 l/hr, 220 VAC, 50 Hz) water maker is indeed the CAT model 277 pump.
Thanks for you early on help with this. I emailed Dessalator at the same time I posted my question on the forum and your reply was days ahead of the manufacturer. But two positives, at least Dessalator replied and (bonus) their information agreed with yours.
All the best,
s/v Liahona SM 335