I am getting all this from MARINEENGINE.COM fyi. I’m working on a ’55 25hp though the earliest marine engine parts manual breakdown is a ’57 35hp which uses the same original impeller currently 0775521 and original housing 0303831.
On the impeller page it says “see note” which mentions an updated impeller and water pump housing. Though it only gives the number for the updated impeller (PN# 0763982) but not a housing PN.
If my digging is correct I believe the updated kit with housing is #395270. It is has the updated impeller as well. I believe this would fit the big twin lower units even though it has 4 bolts instead of the original housing’s 3. I cannot remember if those lower units are drilled and tapped for that 4th hole.
