Hi, we have a 1989 70 hp outboard Merc. Has been running great until the last 2 times out. At low RPMs it bogs down, smokes like hell and won't restart if you turn it off. This last time even over night. It turns over but when and if it catches it dies when put in gear. Running seafoam, plugs were replaced,there is TCW3 in the tank-to be replaced with synthetic when it runs out. No mix in the gas tank needed. Pisses like a 12 year old boy. Is there a standard for mix and idle screws? Do you seat and back off 1 or 2 turns, click your heals and say there's no place like home? Any suggestions? Thank you.