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  1. #1
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    1994 Mercury 2.5L 200 idleing problems

    This is my first post, have been stalking the forums for some time but cant seem to figure my motor out from previous posts.
    I have a 94 mercury 200 that just doesn't want to idle. Bought the motor off Craigslist, was told it had been sitting around for about 10 years. I did regular maintenance on it including tstat, h2o pump, poppet. The motor fired up but died at low speed when shifting into gear (when in water with prop). I rebuilt the carbs and tried running it on new gas and still had the same problem. I understand these motors like to eat stators so I changed that only to still have the same problem. Compression is not the greatest but I would think it should still be able to idle when put in gear. Right now i have the idle set at 1100 rpm and when I shift it in to gear it either idles at 400 rpm and then stalls or just stalls. Motor runs like a top at higher speed just cant get her to idle.

    Any help would be appreciated.
    Port side all blew 110psi Starboard side blew 120, 130 and 110 from top to bottom. Is it rebuild time?

  2. #2
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    If it is equipped with a idle stabiliser try to disconnect that unit, and then reset all timing Again. fine tune tune the adjustment of the carburators. Asuming that you cleaned the carburators. This unit can cause some unforseen Things, and is only used for adjusting the idle ´when you put it into gear, then it will adjust the ignition timing with some degree if the rpm dropps Down under 500 rpm.
    I recommend to having it run a Little rich at idle, just befor it starts stumbling on too much fuel.
    that did it for my inliner 115hp which had problems with the idle stabilizer.
    Last edited by A164; 04-24-2015 at 03:51 PM.

  3. #3
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    There are some very knowledgeable peeps (I am not one of them) on this forum but sometimes they get lockjaw- so rather than leave you with no suggestions here are mine.....
    The compression is off pretty good at 20 psi- and un-even compression is known for causing bad idle. You noted it has been set up for a long time that may change with some run hours- Since one side is quite even it could be carbon build up on the other side which load lead to un-even and higher compression- worth a try with one of the engine tuners-de-carbonizers- won't hurt. 15 psi is normally consider max variation.
    The engine does have an idler stabilizer- used off ebay these are cheap- certainly worth swapping one of the out to see if it helps-
    Do you think it has ever been apart? Are the carbs correct match? Maybe a few posts will get you some real help.

  4. #4
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    Any fuel coming out of the bowl vents at idle? (little brass tubes in carb throat) Sometimes one float can be a little off and cause slight flooding at idle. jm2cts Carbs and low speed timing check would be my prime suspects.

    83 V-King, 96 Mariner, 200 hp ff block 2.5 w/a 28p choppa
    We gotta clean this liberal mess up, VOTE TRUMP TO MAGA!
    Rebuild thread:
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    http://www.screamandfly.com/showthre...cs.&highlight=
    Videos

  5. #5
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    Thanks for the help guys. I don't think it has been apart before based off a visual inspection. The carbs all look good and it seems like the float bowls are not leaking. I disconnected the idle stabilizer and didn't notice a change. I advanced the timing a little at idle and fattened up the fuel mixture and now it seems a little better but still not good. Am I ok running it for a while like this?

    Maybe it's just time for a rebuild.

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    Somebody will correct me if I am wrong on this (and I often am- I have a wife) I think the sleeve on that block is fairly thin and can probably be bore only once. No worse than your numbers are- I would consider hone and rings if no further damage was noticed when torn down.

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    Quote Originally Posted by Seanj85 View Post
    Thanks for the help guys. I don't think it has been apart before based off a visual inspection. The carbs all look good and it seems like the float bowls are not leaking. I disconnected the idle stabilizer and didn't notice a change. I advanced the timing a little at idle and fattened up the fuel mixture and now it seems a little better but still not good. Am I ok running it for a while like this?

    Maybe it's just time for a rebuild.
    If it has been sitting for 10 years, the piston rings may be stuck in the pistons. So if it do not get better after some time, or using Chemicals to loosen Things up. Then it might be a good idea to open it up and do a repair.

    I whould not ad more advance timing to the engine than in the spec. but rich on fuel is ok.
    I have a Mercury 115hp inliner from 1984 and took the idle stabilizer off. and backed off the timing approx. 2 degree at WOT and also a little (½-1 degree) at primary pickup.
    Then I have 2 number bigger main jets in carb.
    That did the trick for me;-) as I think that the fuel was different then than now.

  8. #8
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    A buddy told me that the reeds in the 2.5l were known to crack. Could this be an issue? would this cause idling problems?

  9. #9
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    Quote Originally Posted by CircleHook View Post
    Somebody will correct me if I am wrong on this (and I often am- I have a wife) I think the sleeve on that block is fairly thin and can probably be bore only once. No worse than your numbers are- I would consider hone and rings if no further damage was noticed when torn down.
    When the time comes to tear down I will definitely check how far out the cylinder walls are and try to only hone where applicable. It has been about 15 years since I rebuilt an outboard (last one being a v4 110 evinrude), have yet to tackle a v6. ::Fingers crossed::

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