1987 Merc 45 runs away in seconds, no throttle control

[Flying Scott]

Recently purchased '87 Merc 45 starts fine, goes to full rpm right away, cannot control rpm and must be shut off. Seller doesn't have time to fix it, told me that throttle control may be from a Mariner and they work backwards. Any ideas appreciated! I have worked on older outboards before.
Alan

 

[inthedirtagain]

Had the same issue on my grandfather's boat when I inherited it. Turns out that the throttle was advanced prematurely. Had to sync everything back up. Took all of 10mins worth of adjusting while on the garden hose.