“The pump does not move along the bottom of the bilge as far as I can see and attempting to lift the hose to it did not budge”
Drat. So perhaps someone really did glue the mounting block to the deep bilge!
I’ll tell a story, a real one, from the marina we call home. Three characters: Chris a young bloke who’d bought a steel hull and was cutting out rusty plates and welding in new. Glenn, a middle-aged bloke most famous for being the brother of Tony who plays no part in this story. And Unnamed, owner of a big MV. and to whom I never talked (and so never learned his name). Story goes (and we witnessed part of it) that Chris was walking back to Echo row (which as you will understand is right close to Foxtrot row, where Z has her home and which explains why we knew Chris well). Chris fell in with Glenn, who was walking back to Alpha row and they chatted. After passing Golf row but before they reached Foxtrot, Glenn heard something - a noise, a cry. He encouraged Chris to join him in investigating. Just as well they did - what Glenn had heard was a weak cry for help from Unnamed, who was stuck head first in his deep bilge without the strength and capacity to get himself out and had been in that position, emulating Benito M, for at least 20 minutes. Young Chris pulled Unnamed out. They called the paramedics. Unnamed spent a couple three days in a hospital bed, with the understanding shared by all that he would not have survived another 20 minutes of inversion.
We added a new rule to Z’s book: don’t work in the deep bilge without a buddy right there.
I checked the SPXFlow.com website. A link to a multilingual manual for the Ultima: https://www.spxflow.com/assets/pdf/JPM_IB-123_R05_UltimaBilge_52287-00.pdf But no 3D model.
If you found a retailer carrying a Ultima, you could measure the diameter between the two tabs that lock the pump body onto the strainer. And estimate the force necessary to depress the two tabs.
Then if you’re not prepared to copy Unnamed (with a buddy standing by), I’d suggest seeing if you could make a tool that could lock onto and depress both of those tabs simultaneously.
It might be that it’s not possible - that the dimensions of the deep bilge are such that neither a human hand nor a tool could get in position to press those two tabs.
In which case the only things I can suggest are 1. Paul’s initial idea to just ignore that pump; or 2. to blow or pump big mobs of air or even warm sudsy water under pressure down the outlet hose to clear muck away from the impeller of the Ultima (perhaps using a second bilge pump) and then to use a diaphragm pump, mop, etc to skim and otherwise remove as much of the muck as possible and 3. Rich of Vixen’s idea of putting another pump in series with the Ultima (or at least the Ultima’s strainer).