Mercruiser Engine stops after approx. 1,5h

fjkuth

New Member
Nov 19, 2023
9
Boat Info
SeaRay Sundancer 240 w/camper canvas and Tidewater260
Engines
MerCruiser350 w/Bravo III
need advice!
I‘m in Key Largo with my new to me SeaRay 240, Mercruiser 350 inboard.
engine with only 150h.

after approx. 1,5h drive, the engine suddenly splotters, takes no more throttle and dies.
after approx. 30 minures I can restart the engine Without problem. After approx. 30 Minutes drive, the engine dies again.

i changed already fuel filter and ignition coil - no change so far?

I assume something temperature related?
all engine parameters are normal.

does anybody knows this failure and has advice.

i can’t get a mechanic and have only a few days left on my holidays.

thanks
Franz
 
Details
Year and exact model of engine

When it happens try opening fuel fill cap listen for air being sucked in try restarting. Could be plugged tank vent.
 
2007 SeaRay Sundancer 240 Mercruiser 350
150h on boat and engine.
 
Need the Mercruiser model and serial number off engine cover. Otherwise we are guessing.

Carbureted? Fuel injected? Port or TB? Etc to many variables.
 
Sorry, didn’t know that there are more options…

serial number
OW67544
350 MAG MPI
 
MANUFACTURE DATE
Data tag stated November 2006.
serial OW674544
Family 6M9XM05.7GME
 
Ok so you have a 350 Magnum Multi Point Injection
Computer controlled, cool fuel pump.
Do you have access to any tools?
Voltmeter? Fuel pressure gauge?

Not something you can just throw parts at.
Start simple when it acts up check the tank as i said.
If no gauges see if you have fuel pressure at the fuel rail shrader valve. Have a rag ready.
 
Will check the fuel tank tomorrow!
normal tools like wrench and skrew driver on board and no skilled owner..
thanks for your help!
 
What's your driving habit? pedal to the metal, or cruising around? I don't think heat related, repeatable would take 1.5 hours to manifest itself. Fuel pressure is very important in a MPI. Your fuel gauge would have to be connected and viewable during the failure. You might be above your pay grade for this one. Try the suggestion on the fill cap first, but not in the rain.......
 
Only cruising around at 20-25kt.
today bad weather in the Keys, rainy and windy.
will test the fuel cap tomorrow.
thanks for your help.
 
Could be a number of things, and since you have changed the coil we can rule that out. Often they will have these same symptoms when starting to fail. Also think we ruled out that your distributor does not have an ignition sensor? That is another item that will have these symptoms when starting to fail. Next time this happens I would try a few simple things:

Sound fuel related to me:

Has this engine been running ethanol fuel? If it has and due to it's age I would look at the fuel lines - ethanol fuel will degrade the lines from the inside - even alcohol rated lines. The suction of the fuel pump can cause the fuel line to collapse and create a fuel restriction. If your fuel line is deteriorating, you will see black rubber debris in your fuel filter.

Anti-siphon valve - The barb fitting where the fuel line connects to the tank. It has a spring/ball check valve that over time will corrode and cause problems. This is a cheap easy thing to replace and is probably due on a 15yr old boat.

As others mentioned, check the fuel vent - it could be clogged or have water or even gasoline sitting in it depending if it is integrated with the fuel fill or goes separately to a thru hull vent. Overfilling fuel on the integrated vent lines can cause gasoline to fill a low spot in the vent line. If taking the fuel cap off when the engine stalls fixes it, then the vent is your problem.

Try the easy things first - 1) Fuel Vent 2) Anti Siphon valve 3) fuel line
 
Ok couldn’t solve the problem so far and no mechanic available.

prestent stage:

engine stops as described above
every 1 minute a double beep
on the tach screen appears the message “SYS Fault”
says “ignition, ignition coil does not work properly”

this morning I changed the complete ignition coil incl. the electronic device with the cooling rips against a marine new one.

any suggestions?

it‘s Not thebreezer tube of the fuel tank. No Vakuum in the tank.
 
Ok couldn’t solve the problem so far and no mechanic available.

prestent stage:

engine stops as described above
every 1 minute a double beep
on the tach screen appears the message “SYS Fault”
says “ignition, ignition coil does not work properly”

this morning I changed the complete ignition coil incl. the electronic device with the cooling rips against a marine new one.

any suggestions?

it‘s Not thebreezer tube of the fuel tank. No Vakuum in the tank.
 
I want to give an update on my problem.
a Mercruiser mechanic with a diagnostic computer and a fuel pressure figured it out today.

It’s the water cooled case for fuel filter and fuel pumps.
the cooling does not work properly, reason could be corrosion
In the case. The case gets hot, whereas the water pipes remain cool. On plane the fuel cools the fuel pump and fuel pressure remains steady, wheras in idle the fuel pressure gauge starts to
twiggle first from 32 - 40, the hotter the case gets the wider the range until pressure goes to zero, engine splutters and dies.

the mechanic told me that the case is not available anymore to buy.
he told me, it‘s A bad design, well known and there exists even a service bulletin from Mercruiser.

he recommended to go with a new and better design and to adjust a better one To the system!

any recommendations on that?
does anyone else had this problem?

second recommendation was to get the case cleaned and regularly serviced.

thanks for more insights

happy new year

franz
 
The Cool Fuel system. Surprised none of use thought to look at that. Basically cools the fuel to prevent vapor lock. That is what is happening, the fuel in the lines heats up and vaporizes, fuel pump can’t move vapor, so the engine literally runs out of fuel. When the vapor cools and turns back to liquid everything is fine - until it heats up and vaporized again. Lots of problems over the years - cooling issues like you are having and paint chipping from inside and causing fuel system problems. I do think the the newer versions have solved much of the problems. But they are pretty expensive.
There is a guy “Man Cave Mechanic” that knows about everything about fuel pump issues both Merc and Volvo. He refurbishes these things. Google him, has a website and YouTube channel with good information. I have talked with him myself - I would look at his kits before I bought a brand new cool fuel system.
 
See post #7
You can pick up a cheap fuel pressure gauge kit at Harbor Freight
Handy for anything you think is fuel related on an injection engines.
 

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