'98 Mercury 25 Dying at Idle and Chirping

Discussion in 'Outboard Maintenance' started by rkmurphy, Mar 15, 2009.

  1. rkmurphy

    rkmurphy Well-Known Member

    Took her out on her maiden saltwater excursion today.  It runs great but idles horribly and usually requires choke to start back up.  I don't get it...what could the issue be?  I'll start it...it'll choke up and run a little bit then it'll slowly idle rougher and at a lower RPM until it dies.  Then I choke it to start again and it does the same thing.  If I idle it at a higher RPM it's not so bad.  Once I get running it's fine but if I go from idle to full throttle it will either die or hesitate.

    I also noticed a squeaky/chirpy noise after/while I run the crap out of it but it goes away after a while and it didn't do it at all while I was flushing the motor...no clue what this could be either...hopefully nothing serious...anyone have any insight?

    Another thing I thought I'd add...the water peeing out feels pretty darn hot and even steams a bit.
  2. Brett

    Brett > PRO STAFF <

    RK, it's a '98, that makes it an 11 year old motor.
    When was the last time it had a complete tune up?
    Including replacing the impeller and thermostat?
    When was the last time the carb linkage was synched?
    Are those the original plug wires? Are they brittle or cracked?
    Is the timing properly set? Is the spark advance working properly?
    Is the choke linkage set to open and close properly?
    There is a recommended sequence to doing a tune up.
    Failure to follow it and the outboard won't run as well as it should.
    Invest in a OEM shop manual for your motor.
    Complete specs and photos for the tune-up procedure will show you
    everything you need to make your outboard purr, even at low rpm's.

  3. Unclebob

    Unclebob Well-Known Member

    If it was my motor, I'd start at the fuel hose, look for any leaks as you pump the ball as tight as she'll go, all the way to the pump.

    If no leaks or bubbles, the carb would come off and get thoroughly cleaned, (soaked in cleaner overnight) rinsed, gaskets and needle/seat replaced..

    If that made no change, I'd be looking at the fuel pump..
  4. tailchaser

    tailchaser Well-Known Member

    First.. The squeaking is commonly reffered to as a "lean sneeze". If you're mechanically inclined take the carb off and clean it.  Also check all of your fuel lines and connections. Just because they're not leaking fuel doesn't mean they can't draw air through a leak.

    The carb doesn't need to be "synched" it's a single carb. Only motors with multiple carbs need to be synched. Id does, however need to have the correct air fuel mixture, check a manual to get the correct lean/rich screw adjustment, usually 2-3 turns out.

    Clean the carb
    Change the plugs
    Check the compression, if the motor's been run lean too long the steel ring keeper pins in the piston will swell and score the cylinder..

    From the way it sounds, it's definately a fuel problem.  

    If you want, Give me a call, I'll walk u through it.
  5. rkmurphy

    rkmurphy Well-Known Member

    Thanks tailchaser. I brought it in to a mechanic (family friend) for this one. I was heading down the path you suggested until my future father-in-law insisted on having me taking it in on "don't worry about it ($)" circumstances.

    It was only running lean when idling in my driveway for about 1.5 hours total, 40 minutes of cruising and WOT on a lake, and about the same (40 min) in the Venice ICW and right outside the inlet. Should I be concerned with scoring? Or is that not really enough hours put on her to be concerned about anything?
  6. tailchaser

    tailchaser Well-Known Member

    Na, don't worry about it.
    That little time usually doesn't do much damage.. I'm sure the mech. will do a compression test... That'll tell all.. If the cylinders are even and above 100 psi.. No worries..

    I've had a tohatsu 40 that ran hot until it stopped, and it didn't do any major damage..
  7. rkmurphy

    rkmurphy Well-Known Member

    Motor ran great today and, as far as I know, I solved my shift problem (thanks to a suggestion from AFA Marine). Motor ran and cruised great but I still notice a little squeak/chirp (lean sneeze I'm guessing) after running WOT. Should I adjust the carb slightly more on the rich side? Or just add an oz. of oil to the gas? (there's about 5 gal in there right now)
  8. TomFL

    TomFL Well-Known Member

    "Lean" refers to an air/fuel ratio problem (too much air).

    Adding oil changes the fuel/oil mix but won't change the lean condition (air/fuel) appreciably, and not in the direction you want to go. You should ALWAYS be measuring your gas/oil ratio religiously.

    Tune the carb! You want less air, more fuel, aka "richer".

    You can always try your local library, you'd be suprised at how many ooutboard repair manuals they have there, free of charge for you to borrow and learn from.

    Remember, always learn your mistakes on your buddy's motor, then work on yours once you know how not to blow them up. ;) :D

  9. rkmurphy

    rkmurphy Well-Known Member

    Ooooooooooooo! Stupid me! Haha that makes perfect sense! Well I added an ounce of oil but no big deal...I can squirt a little gas in. I'm as precise as possible with my mixture.

    Then I will loosen the air/fuel screw on the carb just a tweak. A SMALL tweak. That should do 'er.

    Thanks for the clarification. I dunno why I mixed it up. No pun intended...
  10. easy

    easy Well-Known Member

    if after richening the carb it still has a chirp i would look at the recirculation system, i have worked on some of these that the recirc system gets clogged and no lubrication is making it up to the upper main bearing under the flywheel so it runs dry and makes a chirping sound. just something to look at.
  11. rkmurphy

    rkmurphy Well-Known Member

    What's the recirculation system? How would I look at that?

    It only chirps after I run WOT, now...if it was a problem like you're describing would it always chirp?
  12. rkmurphy

    rkmurphy Well-Known Member

    I added an ounce of oil (to 5 gal) and richened the mixture (turned the mixture screw counter-clockwise) a 1/8th turn. Hopefully it's simple and this solves it...
  13. rkmurphy

    rkmurphy Well-Known Member

    Ok so I took it to the place I bought it from today and they were great (Bud Banks Marine). We decided the thermostat and impeller needed to be replaced. So I bought the parts and headed home...

    I go to removed the thermostat housing and as I'm torquing the bolts loose (not forcing them) they go loose all of the sudden. I pull the bolts out only to see that the both broke off and are now stuck in my power head. Absolutely wonderful. A simple job turned into something major because of my horribly bad luck. I shot some WD-40 in...I guess I can maybe try to drill them out...but I'm not doing anything until I find out what's the best way to address this...
  14. TomFL

    TomFL Well-Known Member

    I think gramps just went through this on the same motor, you might try PM'ing him to see how he made out as I know he got them out.

  15. Brett

    Brett > PRO STAFF <

  16. rkmurphy

    rkmurphy Well-Known Member

    Took it back to where I bought it (Bud Banks Marine). They're fixing the bolt issue, replacing the thermostat, replacing the water jacket gasket, and replacing the water pump all for $150. He said he felt bad for me.

    Bud is a good guy. Easy going and straight forward. The place is a hole-in-the-wall but seems like a legit place to take any 2-stroke...he's been dealing with them for a long time.

    Edit: I also learned by looking inside the hole where the thermostat was that the motor probably was not ever flushed. The outside of the cylinders looked fine but the opposite wall was corroded...any way to slow or stop this...other than the obvious flushing regularly. As in any chemicals or additives to help flush out the corrosion and condition the walls?
  17. Gramps

    Gramps Living &amp; Dying in 3/4 Time

    RK - The same thing (broken bolt) did happen to my engine. I tried the bolt extractors & penetrating oil, it didn't help. In the end drilled out the old bolt & retapped the hole. So far so good.... It seems there is a way for the salt water to enter the thermostat bolt holes and cause corrosion. I put antiseize & teflon on the bolts to help guard against future problems.
  18. rkmurphy

    rkmurphy Well-Known Member

    My mechanic got it fixed. I'm supposed to pick it up tomorrow. Supposed...

    He said the only thing that's ever made a slight, tiny difference is applying grease to the bolts. He also said that on Mercs he ALWAYS torches the bolts prior to removal. Even as a preventative measure to prevent breaking. He said that the Mercs were constructed differently than Johnson/Evinrude and Yamaha in that the 'Rudes allow more play (un-noticeable to a normal person) in the bolt which allows them to be more easily freed if there is corrosion (when is there not?). Mercs, on the other hand, are constructed very tight so if there is corrosion, they are probably seized up.

    You live and learn I guess...
  19. rkmurphy

    rkmurphy Well-Known Member

    The shop called today and they said the motor still isn't peeing good, despite replacing the impeller. They said the pee stream is still steaming, too.

    Now I'm supposed to pick up a new housing assembly for the water pump. Does this sound right?
  20. Brett

    Brett > PRO STAFF <

    If the impeller housing is distorted or cracked,
    water will leak out before it can get to the block.
    This is called learning about outboards the hard way.
    Old motors develop all sorts of interesting quirks
    and deficiencies. I've learned buying a used boat
    is a good thing, buying a used motor is a gamble.
    A used boat you can see almost all the surfaces
    and check for defects, but a used motor can look
    great from the outside, and have a world of problems
    that will empty your bank account. Learn to do your
    own work RK, or else buy new motors with the
    extended warranty. Otherwise, in the long run,
    new or used, the cost will be the same.