- Your online store for all types of marine engines and boat parts.
Monday - Friday
9:00 AM - 5:00 PM EST
Click for TOLL-FREE Number
Secure Online Payments
Special $9.95 Flat Rate Shipping
(800) 209-9624 | Home | Contact | Shipping | Returns | Cart View your shopping cart.
Search by Part Number
Enter engine/drive part number.
Original & matching parts for sale.
Manuals & Accessories
Shop by description, item number
or manufacturer's model number.
Why shop with us? Check our reviews! Why Us & Reviews   Boat Repair Forum Boat Repair Forum   Boat Video Gallery Video Gallery
Get instant online access to repair manuals for your Mercury / Mariner outboard. Online Manuals
Order printed Mercury / Mariner service manuals — shipped to your door! Printed Manuals
Use engine diagrams to find & order parts for your Mercury / Mariner engine. Engine Diagrams
Find parts quickly with Mercury application guides. Quick Parts Guide
Results 1 to 12 of 12
  1. #1

    Default Mercury 25hp 2stroke

    Need some help please.
    I can get my motor to start if putting fuel directly into the intake manifold (i think that's what it is called) but it quickly burns the fuel. The gas is fresh and appears to be getting to the carburetor. I've had it running about a month ago but took forever to get it started. At that time once started it ran fine. Can it be something other that the carburetor?

  2. #2
    Join Date
    May 2007
    Inverary, Ontario, Canada - The Great White North Eh!

    Default Re: Mercury 25hp 2stroke

    Yes, it can be many things in the fuel system leading to the carb.

    The tank - vent could be closed/plugged, pick-up could be clogged, fitting could be faulty.

    Hose to the motor - air leak, collapsed, poor fitting, bad primer bulb, bad connector at the motor.

    At the motor - bad/collapsed fuel line, clogged fuel filter, clogged fuel pump, cracked/torn fuel pump diaphram, bad/collapsed line from fuel pump to the carb.

    Carb - dirty or clogged, damaged jet, perforated float.

    Start at the tank and move forward. When you have exhausted all other possibilities, pull, disassemble, clean and rebuild the carb...

    A "professional" is someone who gets paid for their work - it doesn't necessarily mean they are good at it :)

  3. #3

    Default Re: Mercury 25hp 2stroke

    Appreciate the help. I've got fuel running good to the carburetor. I've taken apart the carburetor best I could and hopefully put it back properly. No luck. I hooked it up to the fuel line before putting it back on and tried priming the bulb thinking I would see the fuel coming out the holes, but none. Not sure if there is a proper way to check it before putting it back on the boat. Carb looks clean , nothing obvious.

  4. #4
    Join Date
    Sep 2003
    New Tripoli, PA, USA!

    Default Re: Mercury 25hp 2stroke

    Is the throttle (trigger coil) moving when you open the "choke" (enrichener, actually)? That thin wire attached to the flimsey plastic choke deal is supposed to move the throttle to a higher idle speed at full choke.


  5. #5

    Default Re: Mercury 25hp 2stroke

    The throttle is working. Not sure about the choke. If I keeping putting gas/oil straight into the intake manifold , bypassing the carb , it will continue to run until gone. The mixture does not get past the fuel injector/ carb. Wish I were more mechanically inclined.

  6. #6
    Join Date
    Aug 2006
    SW Ohio, USA

    Default Re: Mercury 25hp 2stroke

    and tried priming the bulb
    Does it get firm when squeezed?
    Fix minor things (replace wear items for preventative maintenance.) that cause major problems before they break.

  7. #7
    Join Date
    Sep 2007

    Default Re: Mercury 25hp 2stroke

    Hmmm. The carb was full of gas when you opened it?
    Set the adjustment to 1-1/4 turns out? Slot screw on the front. That sets the idle fuel mixture.
    Last edited by timebandit; 08-27-2012 at 04:32 PM.

  8. #8
    Join Date
    Oct 2011
    Rocky Mountains

    Default Re: Mercury 25hp 2stroke

    If you are sure you have fuel in the bowl, then it could only be a clogged jet or the adjustment screw is set very wrong. If you have the adjustment screw in all the way tight, no fuel can get through the carb to the engine. Should be set all the way in softly and then backed out 1 1/4 turn to start. If there isn't much fuel in the bowl then you need to check to make sure the float is set correctly. You should be able to attach a clean hose to the carb and blow in it when it is in the normal upright position. When you turn it upside down you should not be able to blow through the hose anymore. If you cannot blow through the hose then the float is not opening enough to allow fuel into the bowl and thus through the carb to the engine.
    Last edited by thebubba; 08-27-2012 at 05:53 PM.

  9. #9

    Default Re: Mercury 25hp 2stroke

    thanks for the suggestions. the bulb is firm and does move gas through. i haven't done anything with the adjustment screw, didn't know what it was til now. before taking apart the carb i dumped most of the gast out by turning it upside down. i took off the bottom part next, can't remember if there was alot of fuel. thanks for the tip on testing the float, i'll give it another try tonight. thanks again.

  10. #10

    Default Re: Mercury 25hp 2stroke

    okay, fuel now seems to be in the carb and sort of working. i believe it was a clogged jet as fuel is definately in the bowl now. i made the changes to the adjustment screw and now know what to do with that. now not sure about positioning of the float. I realized the valve inlet was just sitting in the bowl. put that back. probably simple question, but does the lever float sit above the float, rather than hang down? thanks

  11. #11

    Default Re: Mercury 25hp 2stroke

    Got it fixed. thank you all for your help. had to be in the carb. running great now.

  12. #12
    Join Date
    Oct 2011
    Rocky Mountains

    Default Re: Mercury 25hp 2stroke

    Glad you were able to fix it. enjoy that motor.

Similar Threads

  1. Upgrade 2stroke 25hp to 33hp
    By roy_e in forum Nissan Tohatsu Outboard Forum
    Replies: 6
    Last Post: 05-31-2010, 09:22 AM
  2. 1998 25HP 2STROKE
    By sgt45auto in forum Yamaha Outboard Forum
    Replies: 1
    Last Post: 10-21-2009, 10:46 PM
  3. Mercury 99 2Stroke
    By lutziputz in forum Mercury Mariner Outboard Archive
    Replies: 3
    Last Post: 06-04-2009, 10:01 AM
  4. Outboard motor help 2stroke 25hp Evinrude
    By 2001fz1 in forum Johnson Evinrude Outboard Archive
    Replies: 11
    Last Post: 06-28-2006, 08:18 PM
  5. 99 mercury 2stroke
    By Michael Strudwick in forum Outboard motors archive 2000-2004
    Replies: 1
    Last Post: 02-27-2003, 01:01 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts