I'm in the middle of a swap on a Giant Vac & shaft size will affect HP you can use, I think. My Giant Vac was 16HP with 10" hose & impeller is for 1 1/8" shaft & I have 11HP Honda I was gonna slap on temporarily but it is only 1" shaft. I know 13hp Honda is also 1", but somwhere between 13hp & 16hp shaft goes to 1 1/8". I'm currently trying to workout a trade with a guy on a 20HP Honda Twin. You can go to 13hp but with 8" hose don't know if it will make a change in performance.
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