ok sorry for the long story here but I want to give all the details.
2001 Mobius ls
Engine is indmar 5.7l carb with electronic distributor.
Last fall I had the head gasket replaced on the left side of the engine (I believe 1,3,5,7). Head gasket was blown between 3 and 5 cylinders. A mechanic friend of mine replaced the head gasket for me and we took the boat out and it ran perfect. we ran it for about 3 hours, running it wide open, cruising, idling and shutting it off a couple of times. On the way back to the boat ramp boat was running fine, and then I took the boat out of gear to slow down and I noticed that the engine was idling around 1100 rpm and there was some whitish blue smoke coming from the right exhaust. the following is what I have checked so far to
1. I adjusted the idle set screw all the way down and the rpms never fell. I could adjust it up but
not below 1100 rpms
2. I disconnected the throttle linkage to see if it was sticking open but it was all the way down
3. I replaced the pcv valve and conditions did not improve.
4. I checked the vacuum by using a vacuum gauge and was getting 20 lbs/in. I also checked for leaks around the vacuum hoses, base of the carb, and intake manifold by spraying starter fluid around those areas.
5. I checked timing and it was 6 BTDC.

As of now I am out of ideas and looking for some help