2006 Mariner 115 EFI - Low fuel pressure.

[Damien.]

Hi Guys,

I am completely out of ideas here and just testing the water to see if others have had a similar issue.

We have a 2006 Mariner 115 EFI in the shop at the moment, which is suffering from low fuel pressure. Under load the boat will not even climb to 4k RPM. After a short while, the boat will loose power and the RPM will drop to 2k-3k. At idle and out of the water she runs fine. Sometimes it stalls when shifting into forward gear.

I have inspected and re-fitted fuel lines, changed filters, run my own tank on the engine and even replaced the high pressure pump but no joy. Really wishing that someone has seen this before !

Thanks.

[Downhilldai]

I had a similar problem on an F50 EFi, where the fuel connector at the front of the motor had cracked alongside the small square holes where the fuel passes through, causing air to be drawn into the fuel line by the low pressure pump. This in turn caused a reduced delivery to the VST. By fiddling with the fuel hose connector, I could make a good seal to the fitting, but once the boat was bouncing about at sea, the problem recurred.

May be worth a look.

[Damien.]

Thanks for the suggestion DHD.

Unfortunately if there is a leak, its somewhere deeper in the system.

To eliminate connections etc, I hooked my own fuel line directly to the low pressure pump.

[Downhilldai]

Originally Posted by Damien.

To eliminate connections etc, I hooked my own fuel line directly to the low pressure pump.

Yes, that's what I did on mine.

When you say 'suffering from low fuel pressure', do you mean on the low or high pressure side? I made the assumption that the pressure at the outlet of the low pressure pump is ok?

[jambo]

Hi far be for me to advise a engineer but have you though of the diaphram, I had a similar problem with my 1997 V6 150 last year. Got started but would not go passed 4rpm on the run and would drop down to 2-3rpm.
Hope it helps.

[Damien.]

Its low on the high pressure rail.

and,

The diaphram inside of the low pressure pump has been serviced by myself.

I have a feeling I may have found part of the problem, worn injector seals. Part ordered, will let you guys know the result. Keep the suggestions coming though !

[outboardtech]

Hi Damien , have you sorted your issue out yet??? OK if NOT then Im sure I can be of help to you. When you say low fuel pressure ??? what is the fuel pressure on the valve on top of the rail.Should be 40psi or so. Ok my next step with LOW fuel pressure would be to test the fuel pressure regulator ( this keeps the fuel pressure constant and stabelizes it) I have replaced a few of these babies in the past with low fuel pressure. Or dirt gets inside them. Check this first and let me know. Cheers

[Damien.]

Hi.

I think its sorted, the boat is booked for a water test next week.

Fuel pressure on the rail is now 40psi and shoots up to approx 70 psi when return hose is clamped on the regulator.

I noticed a small pressure leak on the injector seals, whapped on a new set and it seems to be behaving.

I will update soon.

Thanks.

[dirtbox]

Being the main engineer for Quadra Boats i thought you would have been able to sort this one out!!

[Razorbill RIBs]

Originally Posted by dirtbox

Being the main engineer for Quadra Boats i thought you would have been able to sort this one out!!

First post.....

I don't understand , read the OP again!....Surely that's why we use forums like this....wealth of knowledge /assistance etc....can't see anything wrong with asking....