2 stroke back pressure?

[Big-G]

Just read a post reply (TERMANATER) that discussed putting a 2 stroke in a tank and being careful about the depth of water. According to the discussion the caution relates to proper back pressure required by 2 stroke engines. I have always been careful about tank depth but only as it relates to proper use of the water pump. I'm now concerned about my recent fishing trips in very low water where I elevated the trim to clear bottom and only being concerned that the motor was peeing properly. Did I miss read the post reply about back a pressure requirement. If so, can a simple reply educate me?

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