Not possible to have a 90 degree looper powerhead inside a 60 degree 175 HP cowling.----Powerhead to exhaust housing gaskets appear to be different as well.----Any pictures ????
That 22 cubic inch block was built from about 1957 to 1976.-------In 1969 they bumped it up from 18/ 20 HP to 25 HP.----They offered it as 20 and 25 HP up to 1976 model years.----Just a great lightweight motor.
Marketing and decal.-----The original concept was no trim / tilt or oil injection on the 88 HP models.-----There is no difference between an 88 and 90 HP model.
Your location ?----Find a new / used housing , perhaps on E-bay.-----Then bust that housing making sure that the broken screw stays intact.----Use heat to remove broken screw.-----Easy fix here.
The hole in the pump housing gets jammed with that white powder ( aluminum oxide ) and locks it up.---A few taps with a small hammer.----A bit of heat may help here.