My 160 MC stalls out while idling

[glennj3]

For the first time on the water this season we ran great. But later while at or very slow speed the idle would change, slow down. It would always take the gas and run great. But at idle it would stall out unless I I would speed up the RPM.
after coming home I removed the flame arrester. Again it would periodically stall and as it happened I saw gas shooting into the carburetor at the top coming from a hose that comes from the fuel pump.
i just checked / cleaned the screen filter at the carburetor. Then I changed the fuel in line filter.
i only have not changed the water separator.
probably nothing to do with it but there is warm water coming into the engine compartment from an unknown place. I looked while it was running in the lake. Nothing dripping.
thanks for assistance!

 

[QBhoy]

Hi
I hope I’m wrong but symptoms like this can often mean that you are taking in a bit of water through a corroded or frost damaged manifold or riser. Then when you mentioned that you can feel hot water leaking somewhere...it made me comment with such a thing. Might be wrong but just thought I’d say. Was it winterised ok ?

 

[achris]

... and as it happened I saw gas shooting into the carburetor at the top coming from a hose that comes from the fuel pump...

Replace the fuel pump, it has a ruptured diaphragm. That is why fuel is "coming from a hose that comes from the fuel pump"... That hose it there to stall the engine in the event of a fuel pump diaphragm rupture. Everything is working as it should....

Chris......

 

[glennj3]

Then when you mentioned that you can feel hot water leaking somewhere...it
No I did not see or feel any water coming into the engine compartment, but it’s getting in there while running in the lake. It’s warm water and clear. I have a closed cooling system.
thanks.

 

[glennj3]

Oh Chris, I didn’t see your message. That sounds weird, seems like it would just cut off!
can I buy this fuel pump from a local auto parts store, what is the part # or some way to ID it for them?
thank you so much!

 

[Bt Doctur]

Replaces the following part numbers: Mallory 9-35422 Mercruiser 42725A3 (Verify your motor use this entire part number including A3) OMC 509407 Sierra 18-7282 Please ensure your model motor is listed below for proper fitment. This part will ONLY work on models and serial numbers listed below: MerCruiser 140 3.0L 6229718 & UP MerCruiser 3.0LX 3.0L C856559 & UP Match your flange to picture MerCruiser 165 3.7L 6916779 & UP MerCruiser 170 6916779 & UP MerCruiser 180 3.7-LX 6916779 & UP MerCruiser 190 (4-cyl) 6916779 & UP MerCruiser 120 2.5L 6229718 & UP Mercury Marine MerCruiser MerCruiser MC120 2.5L MerCruiser MC165 2.5L MerCruiser MC170 2.5L MerCruiser MC180 2.5L MerCruiser MC190 2.5L MerCruiser MC 2.5L MerCruiser MC 3.0L MerCruiser MC470-1 MerCruiser MC488

 

[Rick Stephens]

Because boats hold all the fumes inside, they aren't open at the bottom like a car. And since any leaked gas sits in the bilge, they are bombs. All mechanical fuel pumps have a diaphragm, when, not if, the diaphragm starts to wear out, on a car type pump it will leak out a vent hole onto the road. No problem cept expensive. In a boat, if it leaks into the bilge, you go boom. So in a boat the vent hole has a nipple and a clear hose goes to the carburetor and dumps into the intake, flooding the engine. No boom.

 

[glennj3]

Thank you Chris, I like to understand things not just accept them.