4.3 LX-Starts and idles fine. Low speed runs fine. Gets on plane w/o problem. Then running underway at 28-32 mph and3500-4000 rpm, engine drops 500 rpm/5-7 mph for about 15-20 seconds, then picks back upto gain what was lost. Continue with steady throttle and cycle repeats again; same time interval rpm/mph loss. If I increase speed, condition just repeats. Fresh tank of gas....Anyone know whats going on?
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