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Mercury optimax 115 2007 Help starts 1-2 secs then cuts off

Bigbuoy01

New member
Hi
boat at dealer who has tried many options
so the boat fires and starts for approx 1-2 seconds then cuts out, turn the key and starts 1-2 sec then cuts out etc etc
whats been checked
batteries 1000 cca
fuel and tanks on boat and put new fuel tank and fuel from dealer
air pressure checked
fuel pressure checked
changed all spark plugs (after this initial new install it ran longer, turned off but again then would not start.
engine controls kill cord etc and ignition switch were bypassed so we know it must be the engine only not external
best weekend weather in the uk for months so not happy
anyone got any thoughts please
 
Since it at least fires - I'd suspect it's starving for gas or too much gas. Try pumping the primer when it starts and see if that helps (i.e. fuel pump/fuel obstruction). Jets WAY off - gets enough gas to start but may be too much to keep it running. Dealer probably tried these but thought I'd try to help.
 
Since it at least fires - I'd suspect it's starving for gas or too much gas. Try pumping the primer when it starts and see if that helps (i.e. fuel pump/fuel obstruction). Jets WAY off - gets enough gas to start but may be too much to keep it running. Dealer probably tried these but thought I'd try to help.
DFI and fuel and air pressures all checked out fine.......cheers
 
Dealer is getting in a engine brain ? And a crank shaft sensor to try both
any experts out there
We are here. This is just a difficult issue to troubleshoot through a keyboard. I would look at the Belt tensioner first....If the belt slips for a half second, the engine will shut down.

If you loose the 5v reference the engine will shut down

Get a remote key harness and hook it straight to the engine and retest,.

If it has smartcraft or any gauges, disconnect them and retest.

The fuel sender hooked to the 5 volt reference ground can cause many many issues.

Like I said, hard to diagnose through the keyboard.
 
Cheers chris
dealer tried all those points mentioned.....basically my engine with his fuel tank and controls so it has to be on the engine nothing external. Today Mercury gave him a engine brain ? and the crank sensor to try off another engine and it's not one of these either.
 
Not sure what test equipment used or pressures but confirmed within parameters for this optimax.
This fault is so consistent I've turn key immediately starts then it's like the key is turned off.....no misfiring etc
not sure if I can video and attach to this forum but will try tomorrow
 
Get yourself a couple of cheap fuel pressure gauges and hook them to the air and fuel rails. Start the engine and pay attention to the air. Let me know what you find.

I shorted direct injector can take the engine down
 
I think you are losing air pressure after cranking and the system is shutting down. How can they tell you everything is within spec if the engine dies after cranking and initial start?

On an Optimax the direct injectors(air injectors) all go open during cranking to push the air pressure up in the air rail using cylinder compression to close down the fuel regulator to push the fuel pressure up to 90 or 100 psi...

After the initial start the direct injectors close, the air compressor takes over and the direct injectors cycle with the fuel injectors.

If the shop where you have your boat at takes off the belt and hooks regulated to 80psi shop air to the air rail and the engine runs your problem is the air compressor...possible bad reeds in the compressor.
 
I've added two videos to show how the engine sounds whilst I try to start it.
one when I release the key as you would normally and the second keeping the key turned and not releasing
 
Hi chris
sorted !!!
Barrus engineer attended today and spent 4-5 hours checking through everything and finally found the problem.
it was a small rubber tube found in the fuel pump area which had broken/ Split and collapsing. Copied in a picture.
i will look for a drawiing/diagram to identify the said part and let you know.
i appreciate you taking the time to offer guidance
image.jpg
 
Did they have the VST tank apart prior to you having the problem? If yes. The damage was done when the tank was put back together. That is how this happens.


Hi
boat at dealer who has tried many options
so the boat fires and starts for approx 1-2 seconds then cuts out, turn the key and starts 1-2 sec then cuts out etc etc
whats been checked
batteries 1000 cca
fuel and tanks on boat and put new fuel tank and fuel from dealer
air pressure checked
fuel pressure checked
changed all spark plugs (after this initial new install it ran longer, turned off but again then would not start.
engine controls kill cord etc and ignition switch were bypassed so we know it must be the engine only not external
best weekend weather in the uk for months so not happy
anyone got any thoughts please

I guess they did not check the fuel pressure.
 
Last edited:
Got new seal $32 �� does it fit fully down onto the pump top or sit half on the top pump tube to seal into the housing please Chris
 
I would push it into the cover and work the pump into it. Then pull it back apart and check it and do it again. Make sure the rubber does not turn.

Still curious how the first shop checked your fuel pressure and said it was good.
 
Ok so part fitted today. Engine started and ticked over nicely for 5 mins with 110 psi on the fuel rail (which I see myself) But it cut off! Starts again fine runs between 2-5 mins and cuts off. All the time the rail pressure is held even when it's cut off
Local dealer been trying all day with Barrus on the phone and still no fix!
Barrus sending their man over to us again Tuesday with VST
 
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