The 1.75 is the engine turning 1.75 times to one rotation of the prop. So going to a 1.62 will be worse on your engine. Every engine is different depending on two stroke or four stroke. Sometimes the two strokes get more power with porting that changes the torque curve and can make the more powerful engine sluggish at slow speeds. Most of my outboard race engines were 1.87.
I would stick with the 1.75.