Just picked up the boat and rebuilt the lower unit. Engine is an '84 Johnson 115. Took it out for its maiden run yesterday. It runs perfectly fine at WOT. At idle, it seems to backfire. Compression is perfect on all 4 cylinders and the plugs looks good. I think it's running lean. I read through my manual but I cannot figure out how to adjust the idle jet (rather, I can't find the idle jets!). There are 2 carbs; each one a double-barrel. There is a rod just before the butterfly from top to bottom. There is an orifice on the top inside of each throat (but they don't turn). Any ideas where to adjust? Or is this a link-and-sync only model?