Aisch, be very careful cleaning out the idle circuit. The idle jet in this series carb is very small and could easily be plugged by a "spec" of debris.
Also do install the scavenge tube as it can eliminate a big bang or burn
. It is a safety devise and it is very simple.
When you do try to start with the rebuilt carb do try using an auxiliary fuel tank and a gravity feed of a few feet will run her up enough to see if all is well. Once confirmed "good" then try feeding with the boats tank. If anything goes amiss do remove and flush the carb immediately. Probably no need to redo but you will at least know if the fuel in the tank is good~~somewhat important.
Do use new lines and freshen the filters for the rebuilt carb if it passes the auxiliary fuel test.
This is a perfect time to add a fuel pressure gage which can save much time diagnosing in the future.
Dave Neptune