Just purchased a 1648 that came with a 1988 25hp evinrude. I took it out with the original owner and when he had the throttle on full and we were just barely moving, so I tried the throttle. It did the same thing for me, until I twisted the throttle as hard I could and the engine finally responded and put the boat on plane and pushed it quite well. It was like it had slack in the cable or something like that. It would be too hard to twist it like that everyday to make the engine perform. What is the problem and or adjustment to fix this. He also said the engine kill switch was broken and/or bypassed if that makes a difference.