Block has 8.2 near motor mount on port side . So 502 confirmed.

I was giving to say that I have a nice set of injectors for your MPIs, but as mentioned it looks like you have cool fuel added to an older set up.

I’d definitely have the injectors serviced.

New pump installed, showing 36 psi with vacuum hose disconnected from plenum. What a PITA it was getting that cool fuel module lined up with the fasteners to the block. I spent more time on that than any other step in the whole job.

Also, I did not see anyone mention this in other threads -- the factory procedure for this job calls for using heat sink compound / thermal grease to facilitate heat transfer where the pump body contacts the retainer plate, and where the retainer plate contacts the cooler body. Likely key to pump longevity.

Should be 43 psi p/n 860349A1

Port motor doesn't hit 43 psi either. Really think both regulators are bad?

Need to first figure out how the motor is configured. Is it a 502 MEFI 3 which was converted to a Mefi 1. A Mefi 2 for a 7.4 mpi installed on a 8.2. Some kind of EFI dystem tied into a mpi or something other.

Right now I dont know what should or should not be there

Well, following the Merc diagnostic charts in manual #23, it states that 34 psi is the minimum allowable pressure with key on. I'm seeing 36. When the pump stops running after 2 seconds, it drops to about 30. If I pinch off the return lines, the pressure spikes up to 60+ psi (I was using a power probe for this test so I immediately let off when I saw the spike).

So, this would indicate that the pumps are both supplying adequate pumping ability, and that the regulators seem to be limiting pressure to 36 psi, which per the manual, is acceptable. In the mish-mash of parts that I seem to have, perhaps a different regulator was used when the cool fuel was adapted to the early injectors?

Ran the boat to see if there is a performance issue or not. Very smooth, accelerated well all the way to 65 @ ~4000 rpm, where I let off because this is a new boat to me and didn't want to overstep my comfort zone. No hesitation, temps all normal right at 160.