2007 Mercury 115EFI Loss of power issue.

[rawleighsmith]

Hello, My name is Lee and I have a 2007 Mercury 115EFI Serial # 1B475550. I'm having a issue with loss of power. When I start it up it runs fine, then when I run it across the lake for about 5 min it just looses power like I'm bringing the throttle back. I bring it back to idle and the whole motor shakes and shuts down. I try to start it back up but it just shakes and shutsdown again. I recently had the main fuel pump replaced about a week ago due to the fuel pressure being low reading about 20PSI which should read about 40PSI. I took it out this weekend and it's still doing the same thing.

Could someone help me out that may know what is going on?

Thanks

Lee

[EuropeanAM]

Lee:

The electric HP fuel pump depends on the lift pump and lift pump float switch, which supply fuel to the system, to maintain a constant flow and volume of fuel in the VST.

If the fuel level in the VST drops, the engine will stumble (and eventually die). This can be a supply problem, a lift pump failure, a high pressure pump failure, or (most common)- a lift pump switch problem.

Might want to look through the following post, as it COULD also be the cause of your problem:

http://www.bbcboards.net/mercury-3-l...tem-first.html

*** NOTE: Ignore references to a primer bulb. YOUR ENGINE DOES NOT USE ONE.

[rawleighsmith]

Thanks for the response.

I had the main pump replaced and it's still doing the same thing. Everything my mechanic has looked at passed all checks. The fuel pressure reads 45 so it's getting the correct pressure to the spray bar/fuel nozzles. Could it be something in the spray bar/ fuel nozzles.

[EuropeanAM]

Lee:

It is possible that there is a problem in the fuel injectors. However, it's far more likely that the problem is fuel SUPPLY to the high pressure fuel pump.

It would be necessary to monitor BOTH output pressure AND the vaccum on the fuel inlet line, AT THE POINT THE ENGINE IS STUMBLING (dying).

My guess is that the float switch in the FSM is failing to function properly... which prevents the LIFT PUMP from drawing fuel INTO the FSM (essentially allowing the engine to run out of fuel).

Essentially the same FSM as was used on the Verado engines... so you might have better luck finding a Verado-Qualified dealer (that's keenly familiar with this FSM and it's diagnosis).

[rawleighsmith]

Thanks again for the response. It really helps out. I talked to my mechanic and he shot it down to a bad Lift pump. Now I'm looking into getting one cheap. I found one online for $197. The part # is 880596T58. Do you know where I could possibly get this pump cheaper or is this a good price. The website is Boats.net. for $197. Let me know if any additional info is needed other than just the part #. I would greatly appreciate any help.

Thanks
Lee

[EuropeanAM]

That's a good price for the pump- PROVIDED that the pump is what you need.

If the float switch is the culprit... you will have wasted that money.

[rawleighsmith]

I talked to my mechanic about the float switch. He said he will look into it and let me know. How would you go about checking the float switch to see if it is bad or not? I'm guessing you would have to change it out and wish for the best. I'm seeing this as a change a part and hope its the fix. What kind of tests or checks can be done to determine if the Lift pump, Float Switch or lets say another thing to look at the (Fuel Presssure Regulator) could be bad. From what I see in the Fuel Module these are all my parts to be concerned about. Thats pretty much everything in the Module. Don I really appreciate all your help on this matter and I hope that we can get this resolved.

Thanks again

Lee

[EuropeanAM]

Lee:

The float switch is a SIMPLE "open/closed" switch. It can be tested with an OHMS meter.

It should be 100% consistent, with no hanging, binding, or irratic operation (whatsoever).

The float switches have been redesigned (several versions) to make them more resistant to ethanol fuels. The REFERENCE HOSE for the fuel pressure regulator has ALSO been redesigned (and I STRONGLY recommend it be replaced, if it has not been).

Latest FLOAT switch: 8M6000359
Latest Reference Hose: 880596A05

[rawleighsmith]

Called my Mech back and he said it was the Float. He ohmed it out and said it was bad. Hopefully this is the fix. I will let you know how it goes. Thanks again Don. talk to ya soon.

[RiverRatMD]

....After this, I'd consider trying a new technician. He sort of sounds like he practices "dartboard diagnostics" ....

Don is one of the true master diagnostic technicians out there. There's a few good one's out there, but not too many.

[rawleighsmith]

You hit that right on the head. That was going to be my next option.

[EuropeanAM]

Glad to hear he performed resistance tests on the float switch.... be sure to report back when that is completed.

Also recommend (as stated above) that the reference hose for the Pressure Regulator (inside the VST) be replaced at the same time. The newer hose is far more ethanol resistant (and the hose SITS in fuel constantly).

[rawleighsmith]

Hey Don wanted to let you know that the float switch was the fix. Took it out Sat and it ran great. I'm gonna find me a new Mechanic next time. What kind of fuel stabilizer do you recommend I add to my fuel? Thanks again for your help.

[EuropeanAM]

Glad to hear that solved the problem.

Mercury QuickCare for everyday use.... Mercury QuickStor for Extended Storage (over 45 days).

[TritonTRXV8]

Glad you were able to get everything worked out. Those kind of problems are always so hard to figure out and drive you nuts. I had the same troubles with my 60 efi merc 2008 model on my bass tracker. I had the same switch replaced TWICE on mine and the main gasket from the engine block to the oil sump TWICE. All done at my dealer by a merc tech. Actually mine had constant problems and i hated it so i traded it in and bought an opti. BEST decision i ever made totally trouble free engine. Has your efi ever had any major oil leaks or made a wierd whistling sound at 2000 rpm? Cuz mine did.