Phester, I agree with doing the de-carb before doing anything else. IMHO, Carbon buildup causes alot of problems including low compression etc. I use seafoam and add it to 3/4 gallon of gas in a small (3gallon) external gas tank. If you go to Iboats forum website (
www.iboats.com) and do a search on decarb you will see the processes in detail. There are two Seafoam decarb products. One is a spray in the cylinders I think named Deep Creep or whatever and another is just "Seafoam" that gets added to 3/4 gallon of gas and running the engine using the mixture or vice-versa. Don't do it in your driveway unless you like cleaning up a horrendus black mess or explaining to the fireman that your boat isn't on fire. I do it on the water on a remote beach or some other isolated location. After de-carbing, replace the spark plugs. I have a home made spark checker that I use to check that the spark on my Yammie can jump 7/16". (Yammie spec.) There is a thread on Iboats forum that describes the homemade spark checker. I wouldn't start with the carbs until after the above has been done. I hope this helps!!
Ed G.