How do I remove, clean, and rebuild the 3 carburetors in a 1994 Johnson 60 hp outboard?

It ran fine last fall but sat over the winter & I forgot to run out the gas. I think bad gas fouled it. When I started it this spring it ran on high idle like always but not on low. Ran it 45 minutes then it ran only on low idle. Now it barely runs on low idle and stalls when I apply any throttle. All repair people tell me I have gummed up carburetors & need a rebuild. Its on a pontoon boat & I don't have a trailer. Repair people don't show up as promised & I need to fix it. Thanks.