Mariner 25 won't idle when warm
Check the plug tips too, usually when the diaphram has holed the excess fuel in bottom cylinder washes the plug clean.
A certain way of telling is if you whip the pump off, block the "out" spigot with your finger and blow through the "in" one you should not feel/hear any air coming through the vacuum hole at the rear. If you do, the rear diaphragm is shagged.
There is a place on this planet for all of Gods creatures.........right next to my tatties and gravy.