Re: 1969 merc 650 leaking gas
There are no seals on the throttle shafts of these carbs. Gas is pouring into the carb and seeping thru the clearance between throttle shaft and the carb body, down the linkage between the carbs.
The solution is to stop the leakage, which is likely coming from a bad float, needle/seat, or poor adjustment.
You'll have to pull the filter covers on both carbs to be able to get the top one off, then 2 screws hold the float bowl cover in place.
The needle/seat are in the float bowl cover, and the float sits freely within the float chamber.
You can grab hold of the little spring sticking out of the float, with the hook of a mechanic's scribe, or just make a hook out of a paper clip or other small wire, and you can easily grab the spring to get the float out.
Mercury sells a "carb packing" or "carb gasket" kit which has the various gaskets you'd need to work on the carb. Normally you wouldn't need the more expensive "carb repair" kit unless the carb was gunked-up really bad.
Most times you'll just clean & adjust/replace needles/seats, upgrade the floats to the new-style ethanol-resistant part, and blow the carb out with carb cleaner (followed by compressed air if you've got it).
Here's a link for some carb parts, with a good diagram to go with:
Mercury Marine 650 (4 CYL.) CARBURETOR ASSEMBLY Parts
Gaskets are toward the bottom of the page. Be sure to verify your serial # in order to get the correct parts.
Here's a good online reference for Merc carburetor work:
MasterTech Marine -- Older Mercury Outboard Carburetor Data
HTH.........ed
