I was running my 21 this weekend with a basically stock Mark IV, 750 Holly double pumper, mechanical advance carb when it went lean at about 3/4 throttle. At least all the plugs are showing lean.
It was Sunday at Parker it looked like Victory At Sea and I was banging it pretty hard when it felt like I dropped a couple of cylinders. Could this cause a float to hang up? Oil temp and water temp were perfect and the plugs look perfect except for looking lean. I didn't have time to try and trouble shoot it before we left.
It still fires right up, idles and made it back to the ramp ok.
i'm no expert, but it sounds to me like u ran the carb out of gas due to the choppy water causeing the floats to bounce up & down...try it again under better conditions!...just my .02 cents
fastrat