Can you seriously do that? If it were higher up it wouldn't be so bad, trying to maneuver through the exhaust and all the cables and wires is a bitch...
Yes. Initially setting it up might be a pain, but it would be a one time pain. You'd have to figure out the thread size for the zerk, which shouldn't be hard, and then they make different hose lengths with threaded fittings on both ends. Thread one end into the pump, run the other one up and mount it wherever you want it and you're home free.
Can't imagine that you're the first one to run into this kind of problem.
Is there an alternative to using a Zerk fitting to pump grease into the bearing on a Jet Pump? It is a P.I.T.A. getting under the hatch with a grease gun trying to reach that little sucker.
BM the ideas above are good ones. Different pumps have some different locations for the zerk and yeah some can be tough to get at. I've done remote grease fitting on many boats in the past either with just a hose and zerk in the end or an actual mounted little custom block with passages to multiple zerks (which you don't need).