Check valve

[engrkenr]

I have a 1968 Merc Model 60 (6 Hp) motor. In the parts list for the fuel pump besides the customary gaskets and diaphragm (ref: 21-22974A-3) are 2 "check valves". What are their function and what would be the symptoms if they were malfunctioning or shy?

 

[Chris1956]

Check valves are one way valves, and are normally part of a fuel pump in 2 cycle outboards. 2 Cycle OBs use the pulses of the crankcase to drive a diaghram in and out. The check valves only allow fuel to be drawn from the fuel line to the fuel tank and pumped to the engine.

 

[Chris1956]

If they don't work, the pump doesn't pump.

 

[tommarvin]

Why not get new check valves, and all other yearly new maintance/winterizing parts you need, you don't want to get stuck out there.

 

[engrkenr]

Chris1956, I suspected your answer on the check valve would be the story and may be the root cause of my lack of high speed performance. The repair kit part drawing shows 2 check valves (with gaskets & diaphragm) but, the exploded view drawing of the fuel system shows only 1 check valve positioned in the line between the pump and inlet to the fuel screen. It would seem to me that only 1 is used but the part kit provides 2 for reasons unknown. Do you know why?

 

[racerone]

???----All these pumps use 2 check valves !!----One lets fuel into the pump and closes so fuel does not go back to the tank.----One opens to let fuel go to the carburetor and closes so that fuel does not come back to the pump.