No fuel pressure when engines are hot after shut down

[Jfrancis3584]

I have a 2000 Carver 350 Mariner with Mercury 350 MAG motors. After running in hot temperatures and sitting for approximately 1.50 hours engines will not restart. I don't have any fuel pressure. It appears something is shutting down the fuel pumps. Once engines cool down they will restart as normal.

[mjk1040]

Me thinks your going to need a tech with a computer to diagnose your issue.

[Viper]

Welcome to the forum.

Qr Bbpost .....It appears something is shutting down the fuel pumps......

Just to clarify; is this a guess or have you actually confirmed that the pumps aren't running? How have you determined you have no fuel pressure?

Qr Bbpost.... After running in hot temperatures and sitting for approximately 1.50 hours engines will not restart. I don't have any fuel pressure.....Once engines cool down they will restart as normal.

If the pumps are running, this symptom sounds like heat soak and vapour lock. Try this; try to repeat the symptom except this time run with the engine hatches off or open and the blowers running constantly.

[mjk1040]

I thought the Merc's had coolers on the fuel pumps. Or was it the Volvo's? Thought I saw that in one of the current threads that had a fuel problem with crap in the tank.

[Viper]

That generation should have Cool Fuel but it's not infallible.

Can you run the engines all day without failure until you shut the engines off?

[Jfrancis3584]

Thank you for the welcome.

I am able to run all day with no shut down or problem. I was afraid to shut down and ran this past Saturday for 5 hours. I was able to restart the engines after sitting for 15 minutes and 50 minutes. The problem seems to occur one to two hours after shut down. I checked the fuel pressure with a fuel pressure gauge and had had 2 or 3 psi. When running the fuel pressure was approximately 35 psi.

I do not know if I have coolers on the fuels pumps. I can check with a more mechanical marina friend this weekend.

When I turn the key without actually turning over the engines I can hear the fuel pump turn on. I didn't have a voltage meter to check for power to the fuel pump.

I have kept the blower motor on while running and after shut down and still experienced the problem. This is the fourth time I had this problem. I was actually trying to recreate the past weekend which I did successfully.

[Viper]

Try it without the hatches in place. Are your engines running at normal temps? What type of cooling system; raw water, fresh water cooled? What temps are your elbows running at? Can you post an engine serial number?

[Jfrancis3584]

Engines are running at normal temperature. I have an open cooling system. Don't know the temps at the elbow. I don't have engine serial numbers at the moment. Can get both this weekend.

This is happening on both engines. Is there anything in common between the two engines?

[Roxanne]

Mercruisers 7.4 (ours are in a 1999 Carver) have installed the fuel cooler under the engine. WE HAD THE SAME PROBLEM AHHHH I have discussed it several times with a lot of advice but no real help. My husband insist it is vapor lock but no one agreed with him about that. This weekend I HAD HAD ENOUGH!!! It makes me crazy!! I called the new mechanic that has come highly recommended at our marina and I explained the same symptoms as you. Turns out, that after running the engines, the water that is used to cool the engines runs a crazy path around the boat and then to the exhaust. When the engine is turned off the water that is being pushed out stops and reverses backs down into the engine place where the gas cooler is!!. It is obviously hot and since the gas cooler is located there it takes a while for it to cool off enough to restart. Basically the mechanic said the hot water is turning the fuel in the cooler to a gas, which is not enough to start the engine. It is trying to start but it seems like it is starving. I am sure there is a much more technical way to explain this! After the mechanics diagnosed it I pulled out my boats schematics to investigate this! Sure enough the diagram is exactly as he said, and GUESS WHAT, Mercuiser makes a correction kit because they are aware of the problem. Are you KIDDING ME> Do we not get cards in the mail to tell us this stuff like when the airbags are recalled in my mustang!!!??? Thought I would share!!

[km1125]

Qr Bbpost
I pulled out my boats schematics to investigate this! Sure enough the diagram is exactly as he said, and GUESS WHAT, Mercuiser makes a correction kit because they are aware of the problem.

Could you make a scan or a pic of that diagram so everyone can see what you're referring to? Do you have a link or a part # for the "correction kit". Sounds like that would be helpful to others too!