Hey mitch.. Yes pull the lower off, and the water pump housing is right there, remove housing and install new impeller, just make sure all of the old impeller is not plugging any of the inlets, hoses, coolers. on a 1990 it should be the normal alpha drive, gen 2 didn't start yet I don't think.
And its not ALFA rubba boat boy.. its ALPHA
would he be interested in a fresh alpha SS drive?
1 nut up front on the lower unit
2 nuts, 1 on each side about 1/3 way back
2 nuts, 1 on each side about 2/3 way back
remove anode above prop
remove allen head bolt thats in the cavity above it.
Its does have a gear lube passage between upper/lower sealed with a o-ring. Make sure o ring is there when assembling.