We have just replaced our original bilge pump with the Johnson 32 also. Plumbing (my least favorite job on the boat) was challenging. Not sure where you are (US, EU, etc), which makes a difference in terms of availability of various fittings. Our local, quite small, West Marine in Maryland, USA, carried Marine East part # 1867548, 1/14” to 1 1/2” reducer. Even that was challenging, still a big leak in one spot where metric met US size, which I fixed by wrapping the male end with several go rounds of Rig Wrap sail tape which worked like a charm.
Be careful, the manual states that if you mount the pump vertically (as was the old pump), you must have it oriented in a certain position, can’t remember which, but again, the manual is clear. That makes running the hoses more challenging with lots of bends and angles.
So far, works like a charm, very powerful.
Aletes, SM 240, Rock Hall, Maryland, heading for St Augustine Florida