"First, I recommend you purcha
"First, I recommend you purchase a Honda workshop manual, It will give you step by step instructions of how to take them apart.
Honda recommends cleaning them in an ultrasonic cleaner. If you soak them in a caustic bath, it may remove the outside coating on the carburators.
If you do not have access to an ultrasonic cleaner, use something non caustic like brake cleaner to flush each passage.
The vacuum gauge comes into play when everything is back together and you are making adjustments to the idle and idle mixture. It is a set of three gauges that you use to vacuum balance the carburators. It ideally should be done with the boat in the water.
The good news is, the 2003 has less vacuum and starting circuit hoses on it, so things are pretty straight forward.
After you have them apart, use a magnifing glass to check for minute cracks in the idle jets (it is the long skinny tube that goes up through each carburator).
It is not a perfect world...so if you do not have the gauges...clean unbalanced carburators are better than dirty unbalanced carburators.
One thing to think about though, a rough idle can be caused simply by unbalanced carburators."