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Power Loss/Surging 2000 Mercury 125hp

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  • Power Loss/Surging 2000 Mercury 125hp

    Like many people, I have a boat and haven't familiarized myself with engine diagnostics. I would like some pointers on where to start checking. My problem is a familiar one as others on this forum. Engine runs fine but loses power some time after throttle up. It can run for 15 minutes at cruising speeds before losing power or can lose power in a very short amount of time. The amount of time is getting shorter and the engine is now beginning to surge at higher rpms. It can clear itself up and run full throttle again without touching anything, but won't last long and act up again. The engine runs fine with muffs on and idles fine in the water, just having problems at higher RPMS. I am thinking fuel delivery or ignition. I have a manual and will read it for help too. People with experience are a better source of help than a manual in my opinion. Any help would be appreciated and probably keep me from being stranded when on the water testing it out. Thanks.

  • #2
    Re: Power Loss/Surging 2000 Mercury 125hp

    Next time it happens have someone squeeze the primer bulb. If it clears then you are having a fuel deliver problem like clogged filter or fuel tank vent clogging.
    Ignition troubleshooting

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    • #3
      Re: Power Loss/Surging 2000 Mercury 125hp

      Thanks for the reply. I forgot to mention that I have a two stroke four cylinder engine. I am going to replace the water separator fuel filter today and inline fuel filter on the motor. They are inexpensive and I am not familiar enough with this boat to know what to look for. I don't want to replace parts for no reason, but since these are cheap and easy it could only improve my situation. I will do more research before replacing anything else. I just need to find out if it is fuel delivery or electrical. I am reading that engines can have somewhat similar symptoms with either type of issue. As I said, I am not familiar enough with this engine to recognize a specific type of issue/cause, but I am going to learn with the help of others. DIY is the only way to go with any vehicle and being self sufficient = not getting stuck on the water and paying unnecessary cost. I have read about peoples experiences with some mechanics replacing unnecessary parts and charging high fees. This is not a road that I am willing to go down. Thanks again for the suggestion. If anyone else has any other ideas and diagnostic steps for a
      beginner. Please let me know.

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      • #4
        Re: Power Loss/Surging 2000 Mercury 125hp

        I have had many bad experiences with boat mechanics. I learned much about boat motors through the school of hard knocks. I sued one and won. I should have sued more of them but they successfully fast talked me. Lessons learned. It's been my experience that most of the people in the boat biz are crooks.
        Ignition troubleshooting

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        • #5
          Re: Power Loss/Surging 2000 Mercury 125hp

          I have replaced water/fuel separator and the fuel filter at the engine. The separator looked good and the fuel filter was had a lot of debris. They were pretty large pieces of some contaminate from the tank I guess. I don't know if it was enough to cause my issue or not, but will find out this weekend. I also did a compression check on all four cylinders and they all measured 125 on the guage. I am very happy at the compression results. I didn't have the opportunity to do a check before buying and was convinced when I saw the condition of the boat (exceptional) and ran the engine.

          I have visually inspected plugs and plug wires, all electrical connections that I could find. I removed the front cover on carbs and visually inspected the ports with the throttle wide open using a flashlight (clean cylinders). As I stated in previous posts, the engine idles smooth and runs smooth at all RPMs unil it acts up then loses power at higher RPMs and will surge some. The first time I ran it at cruising speed to WOT for at least 20 minutes before a little loss of power. Every time after that, the power loss is more dramatic with more surging, but I can run her for at least 15 minutes at crusing speed before she acts up. That may change the next few times I use it, but I am not convinced yet that I need to pursue ignition diagnostics. I will do that next if I find there is plenty of fuel at the carbs when it is acting up.

          I just got the boat from the previous owner and have only had it for two weeks. The engine only has 130 hours on it and is the original one. The boat, motor and trailer are immaculate condition. You cannot find a spot of grime, rust or corrosion of any type anywhere. It ran well the first day and the second day started acting up. Although I have just begun diagnosing this problem, I am really leaning toward fuel or fuel delivery as the cause. The previous owner rarely used it, but always winterized and rigorously kept up the yearly maintenance. He has never had to pay for a single repair and has kept it in a garage.

          I plan on running all of the old gas out this weekend and filling with mid grade. If I still have problems while in the water I will take the front cover off the carbs and watch the fuel intake to see if enough fuel is making it to all four. I will probably try squeezing the primer bulb while it is acting up as recommended and observing. Can you think of anything else I should be trying while on the water testing it out?

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          • #6
            Did you ever get this figured out? My '05 125 EXLPTO exhibiting identical symptoms in a similar situation.

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            • #7
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              Originally posted by Mattchismo View Post
              Did you ever get this figured out? My '05 125 EXLPTO exhibiting identical symptoms in a similar situation.
              Please start a new topic. No one in this one has been around for a long time and the topic is considered dead. Please let it sleep. Thanks.
              BOAT SPECS FORUM HELP STARCRAFT FORUM SHOP iboats
              Please, no PM's (Private Messages) regarding boat/engine problems.
              That is what the forums are for.
              Only forum/moderator issues will be answered in PM's.

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