How does the automatic primer work? Merc 40 hp four stroke -00.

[kryck]

How does the electro mechanic plunger in the primer affect the fuel system? Does it use vacuum from the manifold plate to draw extra fuel up in the carbs?

I'm having trouble getting my merc to run smooth/clean. Also there's a thin gasoline film on the water after a test run. I suspect that the primer doesn't disengage when engine is getting hot. But I have tested the primer directly to 12 volts as the service manual says and the plunger does extend.

Carbs are brand new on this engine. Plugs are new as well.

Any ideas?

 

[kryck]

Re: How does the automatic primer work? Merc 40 hp four stroke -00.

After inspecting the old faulty carbs I've come to the following: when the auto enricher is cold (engine cold) fuel can be drawn up from the bowl into the enricher chamber. From here it's distributed to manifold side of all three carbs through the connecting hoses. As 12 volts is applied to the enricher (engine running) the plunger slowly extends until it have sealed off the path to the bowl and no more fuel can pass through. Only thing I can't figure out is what the hose leading from the top carb to the manifold plate does. Does it provide vacuum or something to the circuit?