Small 4 stroke carb hoses ?

[Swg]

HI, I've just cleaned the carb on a Mercury 5hp 4 stroke. Aside from the fuel lines there were 2x small diameter, perhaps vacuum hose lines? One on the STbd side and one on the top of the carb. When I removed them from the carb the other end came free and I can't see where they attach to if in fact anywhere. Can anyone advise please?

 

[VicS]

HI, I've just cleaned the carb on a Mercury 5hp 4 stroke. Aside from the fuel lines there were 2x small diameter, perhaps vacuum hose lines? One on the STbd side and one on the top of the carb. When I removed them from the carb the other end came free and I can't see where they attach to if in fact anywhere. Can anyone advise please?

AFAICS there are no vacuum hoses ( 2 stroke fuel pumps are driven by vacuum pulses from the crankcase but pumps on 4 strokes are mechanically driven)

Some carbs have a couple of vent hoses that vent through the lower cowling, but I forget what engines I've seen that on. Look to see if the are connections for them in the bottom of the cowling , or perhaps just a grommet, or two grommets, for them to be pushed through

 

[Swg]

I think you are right - I had a good look but can't find a place to which we should attach.
If anyone knows different please do shout out. Terrified of taking the kids out and it's leading to a disaster...

 

[Laysula]

I have a 3.5 hp 4 stroke Mercury and there are two black pipes that exit through holes in the undercowling at the back of the engine.

 

[sarabande]

woah, stop ! Be practical They are there for a purpose, and that purpose is defined in the manual/instructions. Don't use the engine till we have found. out where the pipes go. Please.



EDIT

what is the serial number/model number ?


EDIT #2

Here are the diagrams for Mercury o/boards, but without the model number , I can't point you to the right one.


http://www.boats.net/parts/search/Merc2/Mercury/5 (4-STROKE)/0P401000 & Up/Fuel System/parts.html


EDIT #3 It's almost certain that one is in case the carb float jams, and causes an overflow. That pipe will dribble fuel into the water, rather than over the carb body and engine.

 

[VicS]

If the hoses are those marked #18 in this diagram

then they are the vent hoses to which Bluenote2 refers

I think a feature of the 3.5 and the latest model sof others for which I cannot find diagrams.

 

[Swg]

With many thanks to all, yes they are those numbered 18 in Vic's reply. Safe to believe then that they simply drain into the casing/ sea?

 

[rotrax]

They will be the float chamber vent hose and the float chamber overflow hose.

Whatever you do dont close either off-they should be fixed to their little pipes on the carb at one end and open to atmospher at the other.

If the vent hose is blocked or closed the engine will stop-no atmospheric pressure to push the fuel out.

If the overflow hose is blocked or closed if the carb floods the excess fuel will enter the combustion chamber and could cause all sorts of troubles.

I hope this helps.

Good Luck.

 

[Swg]

They will be the float chamber vent hose and the float chamber overflow hose.

Whatever you do dont close either off-they should be fixed to their little pipes on the carb at one end and open to atmospher at the other.

If the vent hose is blocked or closed the engine will stop-no atmospheric pressure to push the fuel out.

If the overflow hose is blocked or closed if the carb floods the excess fuel will enter the combustion chamber and could cause all sorts of troubles.

I hope this helps.

Good Luck.

Perfect, many thanks once again many thanks to all for confirmin. Now, can anyone sort the weather out for a good sail please..?