I am working on my dad's boat, it's a 1975 Mecury Thunderbolt 500 50HP outboard SN: 4144800. It has dual Tillotson KA26BT Carbs on it, and it just wasn't making any power. If i sprayed carb cleaner in to the top carb while it was running, the rpm's and power came back to normal, so i bought some...
