Where did that half horsepower come from? Dragging a road killed horse behind ya?

Does your carb have an adjustable main jet? If so, turn it out a bit. If not, see these pictures and check the tiny hole in the jets. That's what I would suspect.

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Current fuels: Never let them in anything and always use an additive like sea foam of startron.

As far as vibration, I would look at the impeller. The engines don't vibrate like that unless something is wrong inside. Maybe a hoof in the oil. :)

I have a new carb coming in, but will recheck the old carb when I have it off. Thanks for the thorough follow-up.

Re-check the carb linkage! Sounds like you got it installed wrong, or you left something off. Check the governer linkage. Make sure the float and needle valve are in correctly. Many carbs are replaced needlessly by the ill-informed.

Since I took on the equipment repair for the hardware store 8 years ago, I have never, repeat, never had to replace a Tecumseh carb. They have all been able to clean up with normal rebuilding and soak cleaning.

I'll note that other brands of carbs don't have anywhere near the trouble of Tecumseh carbs when it comes to varnish. The ratio could easily be 25:1

Yes, most of the troubles i have seen with Tecumseh carbs is one or more of those little holes in that bottom bolt is plugged. And, my tip cleaner has made me some quick bucks, over the years!
Ohh, occasionally, i have found other things wrong, but that bolt is the first thing that gets checked, and it is usually the fix!