Mercruiser 5.0 keeps stalling

[e2cpete]

Dewinterized my boat over the weekend (year 2000 5.0L Mercruiser, straight engine - not EFI). The engine started right up, ran for 4 minutes and then stalled. This continued all weekend. I could start the engine without a problem, it would run at any throttle setting for 1-3 minutes and then just die.

I thought I heard a slight "knocking" sound through the exhaust.

I change the Fuel water separator
Added Dry gas
Added Fuel conditioner
Sprayed Carb Cleaner in the Carburater

The boat was stored for winter with almost full tank of gas with gas store additive.

Any ideas?

 

[Fishermark]

Re: Mercruiser 5.0 keeps stalling

If I'm not mistaken, and someone will correct me soon if I am, your engine has a feature where if the computer senses a lack of oil pressure it will shut the engine off after 2 minutes. How's your oil pressure when it does run? If the pressure is good, (and if I'm correct in my understanding), then it could be a bad connection at the pressure switch - or a bad switch - or no oil pressure. Which would account for the knocking!

 

[Don S]

Re: Mercruiser 5.0 keeps stalling

There isn't anything on a carbed engine that will shut it down for overtemp or no oil pressuer. On an EFI engine it will not shut off completely, but will slow down to around 1200 rpm. BUT!!!!! The oil pressure switch does control the fuel pump on the carbed engine, and if the pressure drops below 6 psi, it will shut off power to the fuel pump. IF the oil pressure switch fails completely, you would get power to the fuel pump which would allow it to start, but it would only run for about 20 to 30 seconds. Not minutes.

 

[Fishermark]

Re: Mercruiser 5.0 keeps stalling

IF the oil pressure switch fails completely, you would get power to the fuel pump which would allow it to start, but it would only run for about 20 to 30 seconds. Not minutes.

Thanks for the clarification Don - that's what I was thinking of.

 

[pensacola]

Re: Mercruiser 5.0 keeps stalling

IF the oil pressure switch fails completely, you would get power to the fuel pump which would allow it to start, but it would only run for about 20 to 30 seconds. Not minutes.

Thats what happened to me and it was the oil pressure switch. But like you said it would only run for about 20 to 30 seconds. I would definetely check that though.

 

[e2cpete]

Re: Mercruiser 5.0 keeps stalling

Good advice. I never knew about the oil pressure switch. I do not remember checking it specifically, but I will next weekend when I get back to the boat.

As for the knocking sound, it was not that loud and could only be heard whne outside the boat awhen next to the exhaust. Do you still think that could be attributed to low oil pressure?

 

[Bondo]

Re: Mercruiser 5.0 keeps stalling

As for the knocking sound, it was not that loud and could only be heard whne outside the boat awhen next to the exhaust. Do you still think that could be attributed to low oil pressure?

Ayuh,......

Hopefully the Issue is the Oil Pressure Switch,+ Not the actual Oil Pressure....
And,.....
This Issue could still be causing the noise you heard, as a motor will detonate when Lean,...
Which it would be if the Fuel Pump is being turned Off....