So, just though I’d share something that happened today in my 1983 M20J. I was really high on an approach to landing and decided to side slip to reduce altitude quickly. I stomped on the left pedal for a good 30 seconds to get down to the glide slope and then resumed a normal approach. As soon as I pulled my foot off the rudder, the engine started running really rough and felt like it was about to quit on me (man that grabs your attention quickly!). I was on glide slope at about 300 AGL, so even if it quit, I had the runway made. I gave it a little more throttle, no change. I then switched tanks and after a couple of seconds it smoothed out.
During the pre-landing checks I noted I had about 15 gals total, 8 on the right and 7 on the left (the tank I was on). After landing I did a run-up check. No issues. Several more trips in the pattern. No issues. I even went up to altitude and attempted to recreate the same landing approach with extended side slip. No issues.
Driving home I remembered that small quote from the POH... “Prolonged slideslips, steep descents, or takeoff maneuvers may cause loss of power if the selected fuel tank contains less than 48 lbs. (21.7 kg) (8 gallons - 30.3 liters - 6.6 Imp. Gal.) of fuel“... Bingo!
Moral of the story... re-read your POH and don’t do extended slips in your Mooney if your on a tank with less than 8 gallons unless you want to soil your shorts.