1976 Mercury 500(50hp) carburetor rebuild

[poortenga]

I am shooting gas out of my lower carb when I squeeze the bulb but not when it is running. This motor is otherwise nearly factory condition and I want to avoid screwing up the sync and link that presently is perfect. Any tips on how not to screw up these settings with my carburetor rebuild. I particularly want to maintain the sync between the carbs.
Thanks

 

[Texasmark]

Carb needle valve not seating properly, either due to float not floating, not adjusted properly, or needle seat damaged. Adjusting the low speed jet has nothing to do with the seating of the needle valve and sealing fuel off from the carb.

Squeeze bulb puts a lot more pressure on the fuel system in the engine than does fuel pump pressure when running. If you don't believe me, with the engine stopped, squeeze your bulb till it's good and tight....if you can with your leak...if not leaking it would get really firm and would only cosmetically collapse when you squeeze it.

Conversely, feel the bulb when running.......it's soft,not collapsed, but a long way from the resistance you feel when the engine is stopped, aka lot less pressure on the fuel line and the carb needle valve seat!

 

[poortenga]

I agree with everything you said. I'm wondering though if there is a way to fix this problem without changing the sync between the carburetors and the timing. Can you take off both carburetors together? I don't think my carburetors are dirty inside since the rest of the engine is pristine.

 

[racerone]

Sorry , but the cosmetic condition of your motor has nothing to do with what the inside of the carburetors might look like.----You must take both carburetors off together.---------Reset / repair the float valve and re-assemble.----Do just that and there is no fear of disturbing the mystical " link and sink " on this motor.