Replacing Merc 120 fuel pump; question about lines

[aadst1]

I just finished replacing the fuel pump on a 1983 Mercruiser 120 2.5L inboard, S/N 6303497, but I haven't hooked one of the lines back up yet. Not sure what it is, aside from that it's in poor condition. It's a transparent yellow tube, looks like very low pressure, running from the bottom of the fuel pump up to the side of the carb (not the main fuel line, just to state the obvious). Also, the bottom 6 inches of the tube, the fitting that corresponds to it, the tube right at the outlet of the carb, is filled with some sort of thick, sticky, green mung. The tube needs to be replaced anyway, since it's old and swollen at the ends from the barb fittings, but I'm wondering if this mung is indicative of a problem, and if it could have fouled the carb somehow. Just bought the boat and the PO said the only engine problem was the fuel pump; if you poured the fuel into the appropriate hole in the carb, supposedly the engine runs just fine. If someone could offer some insight as to the nature of the tube, the material inside it, and what it represents, I would be much obliged.

 

[HT32BSX115]

Re: Replacing Merc 120 fuel pump; question about lines

Howdy,


That hose on an engine with a mechanical pump is to indicate if you have a diaphragm leak.

Most automotive mechanical fuel pumps will simply leak gasoline back into the engine crank-case if the diaphragm starts leaking. But if it does that the gasoline vapor will escape into the engine compartment causing an explosion hazard.

The hose allows fuel to be "pumped' up to the carb. Hopefully you'll notice it and see that you must replace the pump. Automotive fuel pumps do NOT normally have the connection. (nor the explosion hazard)

I cannot tell you what the "mung" is. It might be a little gasoline that evaporated and left it behind.....

Just replace the hose.


Cheers,

Rick