Swelling of the ss liner inside the imp. housing is caused by galvanic corrosion between the liner and the aluminum housing- when the impeller touches those high spots (usually the size of a pigeon egg- black/blue in color), it becomes "worn out" instantly and requires rewelding / resurfacing of the outer diameter- if ss impeller. If aluminum, straight to scrap bin. Grinding off the high spots inside a housing is only good for a week. The corrosion inside will continue to grow and keep pushing against the liner. Running it in present condition will/ or has already increased the impeller to housing clearance. There is usually approximately a quarter of a millimeter gap between impeller and housing on a new set up (there has to be a little to keep from touching). If it increases to 0.5mm you'll start loosing power, if more you'll get a "slipping clutch" syndrome- even though your ski does not have a clutch.
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