Mercury 4 hp 4 stroke advice

[davidjbw]

Hello,
I recently bought a Mercury 4 hp 4 stroke Sailpower engine which didn’t run because the carburetor was dirty.
Having now got it running, after a while it does not idle but I think that’s due to a sticky throttle cable.
My problem is that there are bronze in/outlet ports on either side of the top carburetor housing that look as though they should have pipes attached to them. They are about 3 mil O/D and when the engine is running, fuel flows out of them.They do not appear on the exploded diagram of the carburetor. Can anyone tell me what they are for and what should they connect to.
"3 C 6 B Y" is stamped on the carburetor casting and the letters BC molded into it.
Should I just blank them off?

David

 

[VicS]

My first reaction is that the carb is flooding and that you should check the float and the needle valve

 

[davidjbw]

Mercury 4 stroke

Thanks for that (and promptly too). I'll check that; but do you know what these ancillary ports are for?

 

[Lakesailor]

This was my Mariner 4hp 4 stroke. That brass tube at the top didn't seem to have a connector on it. My Tohatsu 5HP was the same.

Like Vic says the float valve must be sticking. clean the tip of the needle with white spirit. It seems to clean the goo off the rubber tip.

​

 

[VicS]

I'd assume that little brass tube was a vent ????

 

[davidjbw]

mercury 4 stroke

Thanks to both of you. Your picture shows the same engine. That's a relief!!

 

[Lakesailor]

If you ever get a problem with the engine dying at higher throttle openings there is an in-line fuel filter beneath the fuel tank that can get a bit choked.
Unfortunately it is so small that you need the correct part as propriety parts seem too big.

 

[the_branflake]

I had similar problems. I first cleaned the carb and it was ok for a while. I didn't really do a good enough job so 2nd time round, i took the carb off again, cleaned it, replaced the fuel filter (as LS says its tiny had to get a genuine one) and also on the fuel tap is another small mesh filter which unscrews. Check that for junk too, mine had all sorts of nasty bits in it.

Its run fine ever since.

 

[DownWest]

Looks very similar to the 3.5 Tot. We had a prob with fuel coming out of one of the vents (both had tubes leading out to under the cowling) The engine was newish and had only run a few hours. We stripped the carb and found a loose rubber bung in the float bowl. This appeared to come out of a hole next to the main jet and had a corresponding shelf on the bowl to keep it in place. Refitted it and problem solved, just a bit puzzled how it came out. BTW, the fuel come out of the vent in a stream for a few seconds, stopped, then came out again.
DW

 

[rotrax]

From the position of the vent it is most likely to be the atmospheric vent. This allows atmospheric pressure into the float chamber so that as the engine cranks and air is passed through the carb, its speed increases and its pressure drops over the venturi-the narrow bit over the jet- and atmospheric pressure then pushes the fuel through the jets to mix with the incoming air. Block that hole-ergo no push from atmospheric pressure. If fuel is coming out-its flooding. As already suggested check the float and needle valve. Good Luck.

 

[davidjbw]

Mercury 4 stroke

Very many thanks to you all. Apart from changing the fuel filter I did all that was suggested and the engine is running smoothly now. If I get any more trouble I will change the filter; which I will order anyway.
Enjoy your boating,
Keep safe,
David