Small hoses on Merc - What are they?

[FredM]

Hi all,<br /><br />I have a 1981 Merc 18hp 2 cylinder. It has a single carb with integral fuel pump.<br /><br />There are two black flexible tubes or hoses about 1/4" dia, each running from near the transfer port covers of each cylinder back to somewhere under the carb (can't see where they are connected to). Do these deliver the pulses for the fuel pump? It's just that my Clymer manual makes no mention of them anywhere - not even in a diagram.

 

[FredM]

Re: Small hoses on Merc - What are they?

Had a good look in the dark with a torch. At least one (can't see the other) goes back on to to crankcase just under where the carb bolts on.<br /><br />Don't think they are for the pump now. Seems the integral pump gets crankase pulses through a drilling in the carb body and directly onto the crankcase.<br /><br />Bugs me not knowing what things are for! And double bugs me when the manual says 0 <br /><br />Any clues???

 

[Paul Moir]

Re: Small hoses on Merc - What are they?

I don't know about your engine in particuliar, but they sure sound like oil recirculation hoses. Basically, crankcase pressure pushes fuel/oil from low points in each crankcase where it would puddle. It is carried through those hoses back to bearings, etc.<br /><br />Aftermarket manuals never seem to mention these at all, even though they're pretty important...<br />EDIT: Just looked at your block. Sorry, those are bleed hoses. They work the other way, caringing puddles of fuel mix back to the cylinders to be burnt.

 

[FredM]

Re: Small hoses on Merc - What are they?

Thanks Paul - and thanks for the parts site too! It has the diagrams and descriptions missing from my manual.