Mercury 850 Thunderbolt 85 hp 2 stroke leaks gas out top carburetor before and after carburetor rebuilds.

[Jlo1985]

Leaks gas out top carburetor. Rebuilt carburetors. Is this a fuel pump problem?

 

[racerone]

No---Fuel pump output is fairly low and depends on the crankcase compression pressure.----Not vacuum.-----So revisit carburetor work.-----Something is wrong with float or float valve.

 

[Chris1956]

That motor sounds like an older (70's) one. The float must be replaced with a hard plastic one. The original ones were foam and would dissolve. Also, the all carb gaskets, inlet needle and seat must be replaced. Some inlet needle seats need the copper gasket, some don't. Install it and see how the float sits. It should be obvious if it needs it.

 

[Jlo1985]

I replaced the floats. The top carburetor float was stuck.

 

[Texasmark]

I replaced the floats. The top carburetor float was stuck.

That is where you find the solution to that problem...stuck or not seating properly.

 

[Jlo1985]

Carburetor was leaking. Will crank but not start.

 

[Chris1956]

Gee, can you give us some more info? What year motor? Does she have spark?

Did you choke the daylights out of her? They need heavy choke to start.