You could slow the engine RPM?....1500rpm impeller means 150rpm AUGER...although to me that looks closer to 200RPM....Is there no way to go 4:1 on the pulley?....This is all to dial it in for later of course, right now focus on making sure it's running and tuned well.You caught it. The ratio is like 3:1 and the impeller is around 1500RPM
There's no way to change that ratio.
PS: It's a cool machine but I'd be figuring out a work around for that low handle bar height.
Operating it hunched over, is going to make it want to ride up deep snow.