You might have problems getting the same shaft diameter. Generally the 5HP engines have a smaller shaft than a 7HP engine. The other problem you might have is that the larger HP engine might not fit in the same area allocated for the smaller engine.

If you want to save $, i suggest you rebuild the carborator on your 5HP engine.

I have a 25 year old ariens snowblower that runs like new. I purchased it used 5 years ago, the previous owner had rebuilt the carborator then. This year I had to replace auger bearing. I always run the gas out of it and change the oil at the end of the season so that it is ready for the beginning of the next season.

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Ray
1998 Mercedes E320, 200K Miles
2001 Acura 3.2TL, 178K Miles
1992 Chevy Astro, 205K Miles