Not sure if this thread is still valid, but a few pics and clarifications may help. Mercury decided to block off the two front holes on the 5.7 chevy block. This makes it a PITA to replace the mechanical fuel pump, but not impossible by any means.
As you can see from the pic of mine, the two bolt holes are not only blocked, they have been heli coiled, or something, with an insert to change them to a fine thread. Makes no difference though, since the holes have a sleeve that prevents them gong all the way through.
If the giant glob of grease doesn't work, then taking off the whole cover will get the job done, but also with a glob of grease. I use marine grease for this job.
Also, don't forget the overflow. There is a tube that goes from the pump to the carb to dump excess fuel into the intake.
For some incredible reason, mechanical marine pumps have two diaphrams . In the event the main fails, it will pump fuel to the intake. The likelihood of this happening is about the same as winning the Powerball.
At any rate, if you switch to a highly flammable electric setup, you may need to block off the vent on the Q jet.
