25 horse merc efi 4-stroke losing power

Discussion in 'Outboard Maintenance' started by TomFL, Jan 1, 2009.

  1. TomFL

    TomFL Well-Known Member

    Ran it Xmas day with 2-week old gas, ran like a top as always. Starts first pull, purrs like a kitten and ran strong all day.

    The next morning before heading out put 2 gallons of new fuel in it, put the boat in the water and went 200 yards and the motor lost rpm leaving me to limp home at about 9 mph. No lights or buzzers went off. Dumped the gas out of the under-cowl fuel filter, removed the line from the motor and pumped a bunch of gas from the tank into a clear gatorade bottle and saw no water in either, re-attached the fuel line and started it up, first pull as always. Neither seemed to help.

    Fuel bulb was mildly soft, pumped it while running to see if she would gain rpm but no help.

    Checked vent on gas tank to be sure it's open. Even tried running with one of the screw-off caps open to be sure it was not a vent issue.

    Went home, again dumped the gas out of the under-cowl filter and set aside to let dry, drained the under-cowl reserve fuel tank thing, dumped all the old gas through a water seperating filter but did not see any contaminents. Did not put old fuel back into tank. Re-filled the tank with new gas from another gas station. Went back to the ramp and same problem.

    The motor starts first pull and runs to about 1500 rpms +/- with no issues. It will run full throttle for about 1 minute, then loses power. If you idle for a while and hit it again same issue.

    It will idle all day with no issue. Stay below 1500 rpms and it's fine.

    If it's a fuel starvation issue, wouldn't the bulb be collapsed and the rpm increase if I pump the ball to rock hard?

    Any thoughts before I bring it in? Honestly the EFI isn't as user-friendly as the old carbed 2-strokes!!

    It is under warranty, would prefer to find the issue myself rather than leaving it with a dealer for a few days if it's something simple.

  2. Brett

    Brett > PRO STAFF <

    Sounds like the engine overheat rpm limiter is functioning...

    Quote from merc:

    Engine Guardian will signal that there is a problem and will
    automatically go into a self-protect mode by reducing engine RPM.

  3. TomFL

    TomFL Well-Known Member

    Was a thought of mine as well, but that would mean the buzzer AND the warning light are malfunctioning.

    Pisser pumps like a champ. Water is hot to the touch, maybe a little warmer than I would be used to with a carbed motor, but I'm not sure that's abnormal given this is an efi motor. You can hold your hand under it of course.

  4. Brett

    Brett > PRO STAFF <

    Buzzer and light are part of the secondary circuit?
    Primary circuit is the rpm limiter and is kicking in but not
    activating secondary. Good thing it's under warranty.
    Could have a sticking thermostat that didn't show up
    during the factory test, but is now. Opens partially
    but doesn't allow water to cool the engine enough.
    Symptoms you describe sound like the limiter is doing it's job.
    Possible sensor malfunction could also cause the limiter to kick in.
  5. TomFL

    TomFL Well-Known Member

    At the dealer now......We'll see....

    I will say the LT25 was about 1/3 the size of the next smallest boat at that dealer, but I about had to fend off people asking about it. Sure raises some eyebrows, that little rig.

  6. TomFL

    TomFL Well-Known Member

    Solved. Fuel pump.

  7. noeettica

    noeettica Well-Known Member

    Did they cover the Fuel pump under warrenty ...

    They would NOT cover mine ...

  8. Flyline

    Flyline Won &quot;Do More With Less&quot; Award!

    The dealer have to cover your motor when it's on warrenty and it's their policy to do it. If they dont do it then complain to merc customer service then it will solve the plm. The dealers always smell money for labor.
  9. TomFL

    TomFL Well-Known Member

    Don't know yet, that's why I posted about finding a good parts source online. Apparently there are two fuel pumps on this motor, which would probably be the reason the motor didn't react when I pumped the ball. The hi-pressure pump is the one that went, and they told me "they have to take it apart to look for corrosion, in which case it won't be covered".

    Sounds like I already know what the answer will be.

  10. Flyline

    Flyline Won &quot;Do More With Less&quot; Award!

    they smell money!!! :mad:  that's full of shit
  11. noeettica

    noeettica Well-Known Member

    Here it is the "local" Dealer wanted something like $135.00 for it

    Got it online for like for $52.00

    Seized up tighter than a Drum !

  12. TomFL

    TomFL Well-Known Member

    Yeah, back when I had that 18-horse nissan, the dealer wanted almost $100 just for the male engine fuel fitting. $100 for a fuel fitting!!!!

    I asked them if they were mistaken but no.

    I wound up ordering all 4 fittings (tank and motor) plus a new carb kit for about that with shipping online.

    If the price is somewhat close I will always try to do business locally. But if it's shockingly high, I really just don't know how these businesses will survive with the internet around. Especially considering the economy right now, which forces many to shop around even more.

    We'll see what the local merc dealer says about my fuel pump.