Double engine failure in ten minutes

[Doubletrouble 1965]

After a trouble free summer I had a double engine failure with my Mercruiser 3.0 efi engines.
Both have 11:00 hours and are completely independent. They only have the boat in common.
Both failures appear to be similar. No spark, fuel pump comes on and turns off as normal but
plugs are dry. Something is telling the ECU to shut motors off.
Any ideas. Anybody convert an EFI engine bact to carb and points? Not just kidding.

 

[flashback]

I bet the fuel tank is common, I would start there.

 

[Scott06]

After a trouble free summer I had a double engine failure with my Mercruiser 3.0 efi engines.
Both have 11:00 hours and are completely independent. They only have the boat in common.
Both failures appear to be similar. No spark, fuel pump comes on and turns off as normal but
plugs are dry. Something is telling the ECU to shut motors off.
Any ideas. Anybody convert an EFI engine bact to carb and points? Not just kidding.

No shared batteries or charging system via shore power?

 

[alldodge]

After a trouble free summer I had a double engine failure with my Mercruiser 3.0 efi engines.
Both have 11:00 hours and are completely independent. They only have the boat in common.
Both failures appear to be similar. No spark, fuel pump comes on and turns off as normal but
plugs are dry. Something is telling the ECU to shut motors off.
Any ideas. Anybody convert an EFI engine bact to carb and points? Not just kidding.

Need more info, explain more about what is going on.
Motor serial number?

Were motors running and just shut off, or they crank and won't start?

Plugs should not be wet, shouldn't actually see any fuel on them, and if you did, then that's what's wrong

When key is turned to ON do you hear a beep, or 2 beeps?

Does the boat have a kill switch?

 

[Doubletrouble 1965]

No shared batteries or charging system via shore power?

Thanks for reply. No shared fuel tank separate batteries. The idea
was to have some degree of redundancy. Correction,the engines are
Mercruiser MPI not EFI.
I did check fuel filters. Plenty of fuel at Shrader valve at fuel rail but
spark plugs dry.

 

[Scott Danforth]

check compression

check fuel pressure

check contents of fuel filter

check antisiphon valve

check fuel pickups

if I were to bet, my bet would be bad fuel or no fuel in the tank

 

[Doubletrouble 1965]

Need more info, explain more about what is going on.
Motor serial number?

Were motors running and just shut off, or they crank and won't start?

Plugs should not be wet, shouldn't actually see any fuel on them, and if you did, then that's what's wrong

When key is turned to ON do you hear a beep, or 2 beeps?

Does the boat have a kill switch?

Problem occurred during a one hour slow cruise @1500-1800rpm. Port engine died and sounded like fuel starvation. Starboard engine got us home
and then died at idle. Neither motor would restart. Switch on gives one beep
as before. Plugs are dry.

 

[Doubletrouble 1965]

Problem occurred during a one hour slow cruise @1500-1800rpm. Port engine died and sounded like fuel starvation. Starboard engine got us home
and then died at idle. Neither motor would restart. Switch on gives one beep
as before. Plugs are dry.

Serial # 1A346598 is Port engine. I don’t have the other number handy but
both were identical and purchased at same time. Would a fuel pressure
issue cause the ECU to shut down the ignition?

 

[alldodge]

I'm betting bad fuel, did you just fill up maybe, or was there a heavy rain/storm and got water in the tank maybe?

Remove filter and dump it into a clear container to see if its clear and smells like gas

and just the one serial number is good

 

[QBhoy]

Odds on to be fuel related.

 

[Grub54891]

Yeah fuel. Following.

 

[Doubletrouble 1965]

Yeah fuel. Following.

Update
Many thanks for all your suggestions. I have spent the last couple of days
arranging to have the boat towed the eight miles to where it can be hauled
out. This was complicated by some bad weather. We finally managed it today in rough weather before the Government Dock closed for the season.
Tomorrow I will continue to investigate my problem.
Drain and analyze fuel
Check for voltage at fuel injectors
Any other ideas?

 

[Scott Danforth]

Start with fuel pressure. With MPI, you should have about 45psi

 

[alldodge]

Being that both motors had the same issue then don't see the need to check spark or injectors. Checking fuel pressure would be good to know, but betting just checking the filters and quality of fuel may give insight

 

[QBhoy]

Hi. What’s the history behind the boat and engines and their relationship with each other ? Were these engines newly fitted to the boat ? And was this the first run out with them when this happened? Was just thinking around the installation if so…in particular around the shift interrupt switches being contacted by a poorly set up cable assembly. Or perhaps around the lanyard kill switch installation (although unlikely, I think the fuel pump doesn’t come on when this happens) Or even the batteries being not charged sufficiently by the alternators or a fault in their wiring ? Almost sounds as if you ran out of electrical juice perhaps. Then what can happen is the batteries can recover enough to turn the engines over, but whilst that is happening, the load taken by the starter can mean that there isn’t sufficient power to fire up the ignition to fire. If it’s not fuel related…I’d be looking around there for sure.

 

[Doubletrouble 1965]

Hi. What’s the history behind the boat and engines and their relationship with each other ? Were these engines newly fitted to the boat ? And was this the first run out with them when this happened? Was just thinking around the installation if so…in particular around the shift interrupt switches being contacted by a poorly set up cable assembly. Or perhaps around the lanyard kill switch installation (although unlikely, I think the fuel pump doesn’t come on when this happens) Or even the batteries being not charged sufficiently by the alternators or a fault in their wiring ? Almost sounds as if you ran out of electrical juice perhaps. Then what can happen is the batteries can recover enough to turn the engines over, but whilst that is happening, the load taken by the starter can mean that there isn’t sufficient power to fire up the ignition to fire. If it’s not fuel related…I’d be looking around there for sure.

 

[Doubletrouble 1965]

Update
Began with starboard engine.
1. Charged battery for 11/2 hours.
2. Removed and dumped fuel from fuel filter. Fuel a little orangey but no
sign of water contamination.
3. Jumped FI pump to remove any fuel.
4.checked Injectors with tester. Good.
5. Checked fuel pressure 43psi.
6.Checked spark with tester. Now getting spark.
Engine started,initially ran rough then settled down. Result.

Starboard engine
Started and ran smoothly without any action on our part!
Conclusions
The two engines quit as a result of either a low fuel level or low
Voltage resulting from an extended low speed cruise. Once the
batteries were either charged or recovered on their own spark was
restored. Also the boat is now parked on an incline providing more
positive gravity feed for fuel.
Thanks QBoy for the low voltage suggestion.
These electronic ignitions are obviously very sensitive to voltage and
May not tolerate extended low engine speeds.

 

[alldodge]

Fuel should be clear, the orange color is not good and its either contaminated or old

 

[QBhoy]

Update
Began with starboard engine.
1. Charged battery for 11/2 hours.
2. Removed and dumped fuel from fuel filter. Fuel a little orangey but no
sign of water contamination.
3. Jumped FI pump to remove any fuel.
4.checked Injectors with tester. Good.
5. Checked fuel pressure 43psi.
6.Checked spark with tester. Now getting spark.
Engine started,initially ran rough then settled down. Result.

Starboard engine
Started and ran smoothly without any action on our part!
Conclusions
The two engines quit as a result of either a low fuel level or low
Voltage resulting from an extended low speed cruise. Once the
batteries were either charged or recovered on their own spark was
restored. Also the boat is now parked on an incline providing more
positive gravity feed for fuel.
Thanks QBoy for the low voltage suggestion.
These electronic ignitions are obviously very sensitive to voltage and
May not tolerate extended low engine speeds.

No probs. It’s defo a real thing with these type engines. I was so confused one spring launch…when my mpi wouldn’t start at all…despite cranking over fairly healthily. Charged the battery on boost for half an hour…fired right up. Further verified, by another 2 mpi and 1 efi outboard boats launching from the boat yard that day and having similar issues. The starter just takes the juice away from the rest of the system…just won’t play ball with anything other than a really good battery.
Only thing in my mind with yours, might be around thoughts of why it happened to you when the boat should have perhaps been keeping the batteries healthy when running. Perhaps worth keeping an eye on the charge output you are getting from the alternators and making sure you are seeing that at the batteries too.

 

[Scott Danforth]

2. Removed and dumped fuel from fuel filter. Fuel a little orangey but no
sign of water contamination.

Define "orangey"

Sounds like fuel is old and turning to sludge with some contamination

Good fuel should be almost perfectly clear with a very slight amber/blue hue