During preboating maintenance engine ran & powered up as it should. We changed the spark plugs, cleaned the distributor. Everything ran fine. We launched & went to speed up & at full throttle the engine the rpm would not go above 1000. We have a 17in stainless steel prop. On a 77 wellcraft fisherman 16ft well under weight capacity. Currently sitting water with 3 frustrated children who want to tube. First outing so we are a little frustrated too. Help, ideas, suggestions?