2006 Merc 115 4 stroke problems, hope someone knows the answer...

[bigjimmcbob]

4 year old Mercury 115HP 4 stroke

Haven't had any issues with it besides a blown EFI micro controller (left me stranded ).

Always starts immediately, been trolling on Lake O with no issues.

There's < 200 hours on this motor.

 

On her maiden voyage had issues with the fuel line. On 2006? + EFI's there;s no primer bulb, the fuel pump pressurizes the line. We tightened the clamps and all was well.

 

So this year maiden voyage (after 2 nice salmon) it stopped while trolling.

Restarted, 15 min later stalled again.

It had 80L of stabilized gas + 40L of fresh gas/

 

This time on restart, didn't sound right, "putter putter" etc.

At full throttle it was OK, 1/2 throttle OK for a bit, but at idle very bad and stalled often.

Figured we'd better pull up and get back to port.

 

At home, I put the muffs on and hooked it up to an external tank hoping it was bad gas.

I let it burn out the "bad gas".

Hooked it up to a fresh 20L tank.

Noticed the "pressurization" of the new line I had to the external tank had air pockets it in. (It was tight to the external tank)

Same result, putter puttered and stalled often.

I then disconnected the line, and after about 2 min, the motor ran smooth again with no gas tank connected until the gas in the motor ran out.

 

I tried again to hook up the "fresh gas" and again putter puttered with noticeable air in the line.

But again after 2 min the motor ran smooth and all the way until she ran out of gas internally (5-8 min).

 

 

So is this a fuel pump problem or perhaps an issue with the line internal to the motor that is not air tight? It sounds like the motor just isn't getting enough fuel, but its odd that it runs just fine when I disconnect the fuel line!

I've ruled out gas as being bad, so its odd to me it runs good after its not sucking gas from a tank. Does this mean its just consuming fuel that the pump has already sucked and that its now full its OK? I'm going to take it in to my Merc dealer, just don't want to know what might be happening to this motor before I take it there.

 

thanks guys,

Big J.

[DRIFTER_016]

I gather you have an inboard fuel tank, right?

It sounds like a stuck anti siphon valve on your tank or a clogged vent line.

Disconect the vent line at the tank an blow through it or use compressed air to clear it out. If that doesn't fix the issue you can remove the anti siphon valve (usually it is inside the right angle connector on top of the tank(remove the connector). Replace it with a plain (non anti siphon connector) and see if it runs correctly.

Other than that it could be a fuek pump issue.

Edited June 21, 2010 by DRIFTER_016

[DanD]

At full throttle it was OK, 1/2 throttle OK for a bit, but at idle very bad and stalled often.

Figured we'd better pull up and get back to port.

 

but its odd that it runs just fine when I disconnect the fuel line!

I've ruled out gas as being bad, so its odd to me it runs good after its not sucking gas from a tank.

 

 

Not sure how the fuel pressure is regulated or what the fuel pressure should be but with your description the engine may be over fueling at idle?

 

Why I’m thinking this is with the fuel line disconnected it runs ok; you’re slowly starving the engine of fuel until there’s no fuel pressure left and then stalls?

 

Being an electronically controlled system it may not actually be an issue with the fuel system but a sensor telling the computer inaccurate information. Something like an engine temperature sensor for example; if it’s gone a skew and telling the computer the engine is cold; the computer will in-turn dump fuel into the engine. A cold engine needs extra fuel to run correctly but a warm engine will begin to flood out.

 

Just guessing here but when it’s doing its thing “putter putter” does it smell rich (heavy exhaust fumes)?

 

Dan.

[Fish Farmer]

My guess would be your fuel line is sucking air, connection to the motor may have a nick or crack in the O ring. The fuel hose could be getting air. This was a problem with most of my OMC's

Just a thought. Remember, cheapest first.

[bigfish1965]

Inline fuel filter?

And like fish farmer said..cheapest first. Try running off a borrowed portable tank and full line and see what happens. Eliminate all other possibilities and whatever than remains, no matter how unlikely must be the answer.

[bigjimmcbob]

Thanks guys.

Ya I hooked up an external tank, same problem. It's getting air someplace. External hose to tank seems solid.

I think my 115 EFI has 2 pumps, the first pump pressurizes the line, and the second pump moves fuel to the internal reservoir. Seems when the fuel is up there and the first pump shuts down the engine runs OK.

 

I sent her in today just don't have the time to play with it midweek.

 

thanks again

[DanD]

Please let us know how this has worked out and what the issue actually is/was.

A thing like this gets my interest up; what can I say I’m an auto tech and like hearing problems and fixes.

It might apply to something I’m working on the future?

 

Dan.

Edited June 22, 2010 by DanD