97 explorer carb issue?

I have a 97 explorer/ 85 hp 717 rotax engine. I had a few issues and seem to be unable to keep it runing. 1st I had to remove the oil inj cover to pull out a screw that jammed in the rotary valve plate. We ran it a few times after and the exhaust pipe vibrated off the exh manifold. fixed that and it ran ok. We took it to Fla and it ran ok the fiest day. The second time it killed at the dock and we could not get it started again. New plugs,wires(and spark),fresh fuel,new filter, but nothing .I sort of got it running at home but it idles for about 5 seconds abd u cant throttle up. That kills it for sure. I squirt a little fuel in the carbs but that seems to choke it too. I thought of the two small filters in the carbs and might see if I can remove them> Funny though , it ran so well in Fla , then killed. I also made sure the impellor was clear. nothing there. I also thought of the fly wheel spinning the woodruff key , but two dinky screws broke off at the head trying to look at the flywheel , so i abandoned that idea. Also a dealer in La. thinks that us unlikely. Not sure if timing all of a sudden crapped out> anyway I am thinking of looking in the carbs for fuel issues. Also what are the faults of replacing the factory crimped clamps with ss worm drive clamps? ay thoughts are appreciated..................jim