1972 50 hp Johnson with hydro electric shift won't idle

[tinocker]

I have a 1972 50 hp johnson that won't idle. The throttle cable seems to be working fine as I can rev it up for cold start, but when I put it to run it dies. The motor runs well otherwise, just won't seem to idle right. I have adjusted the cable, and it seems to be moving the carbs. However where the linkage connects to the timing advance lever seems to be the problem. When I advance it by hand the motor revs, but when I slow it down to the adjustment screw it dies. I have turned this screw all the way in with no results. Any ideas?