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87 Mercury Classic 50 won't throttle past 3000 RPM?

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  • 87 Mercury Classic 50 won't throttle past 3000 RPM?

    Bought a 1987 Bass Tracker with an '87 45 HP Mercury on it. Floats were stuck, so I had to have both carbs rebuilt. Took it out for the first time this evening. Went right up on plane, and I was running 5,000 RPM at WOT (about 30 MPH). All of a sudden, the motor bogged down, and died. Started right back up, but now won't throttle past 3,000 RPM in gear and won't plane out. In neutral, it is fine...throttles right up. What do you guys think is going on? Signed...frustrated in Missouri!
    --------------------------------------------------------------------------------------------------------------
    "Three-fourths of the Earth's surface is water, and one-fourth is land. It is quite clear that the good Lord intended us to spend triple the amount of time fishing as taking care of the lawn." ~Chuck Clark

    My New Bass Tracker


  • #2
    Re: 87 Mercury Classic 50 won't throttle past 3000 RPM?

    Pull the spark plugs out and look to see if one or more are sooted and fouled.

    Check for spark on all cyl's.

    One dead cyl, no spark or fouled plug, and the engine will not perform under load, yet will rev freely in neutral.

    Comment



    • #3
      Re: 87 Mercury Classic 50 won't throttle past 3000 RPM?

      I pulled all the plugs and looked at them. The only one that was dry was the bottom one. Other 3 were wet w/ fuel and had a little black sludge pooled in them. Hard to really tell because the plugs are brand new. I took some pics, will post a little later. If the top 3 aren't firing, am I looking at the switch box as the problem. One other thing...my 6 gallon tank only had about 1/2 gallon of gas left in it. I was only out for about 1 hour, and 30 minutes of that was idling back to the ramp. Seems like it's pulling a lot of gas. Also, the bulb was soft when I got it home. Thanks so much for thee help. Aaron.
      --------------------------------------------------------------------------------------------------------------
      "Three-fourths of the Earth's surface is water, and one-fourth is land. It is quite clear that the good Lord intended us to spend triple the amount of time fishing as taking care of the lawn." ~Chuck Clark

      My New Bass Tracker

      Comment



      • #4
        Re: 87 Mercury Classic 50 won't throttle past 3000 RPM?

        Photos of my plugs can be seen at the following addresses:

        http://www.flickr.com/photos/2447998...7618016421208/

        http://www.flickr.com/photos/2447998...7618016421208/

        http://www.flickr.com/photos/2447998...7618016421208/

        http://www.flickr.com/photos/2447998...7618016421208/

        can you guys tell me anything from these photos? thanks again for the help. not sure what i would do without the advice you guys give on here. AC.
        --------------------------------------------------------------------------------------------------------------
        "Three-fourths of the Earth's surface is water, and one-fourth is land. It is quite clear that the good Lord intended us to spend triple the amount of time fishing as taking care of the lawn." ~Chuck Clark

        My New Bass Tracker

        Comment



        • #5
          Re: 87 Mercury Classic 50 won't throttle past 3000 RPM?

          I had the same issue with my Classic fifty and I had a piece of the fuel pump get stuck in the jet of one carb.

          Comment



          • #6
            Re: 87 Mercury Classic 50 won't throttle past 3000 RPM?

            thanks phil. i planned on pulling my fuel pump apart this weekend. maybe i'll find it's torn apart. just not sure at this point. AC.
            --------------------------------------------------------------------------------------------------------------
            "Three-fourths of the Earth's surface is water, and one-fourth is land. It is quite clear that the good Lord intended us to spend triple the amount of time fishing as taking care of the lawn." ~Chuck Clark

            My New Bass Tracker

            Comment



            • #7
              Re: 87 Mercury Classic 50 won't throttle past 3000 RPM?

              thanks for the help, guys. when i had the carbs rebuilt, he didn't replace any of the fuel lines or rebuild the fuel pump. is that something you would recommend (if compression and spark check out ok)?

              i did buy a new merc supply line and tank when i bought the boat, so i should be good there.

              is it possible one of the diaphrams or something let loose in the fuel pump and is clogging a jet on the carb? i really don't want to rebuild those carbs again.

              thanks again for the help. ac.
              --------------------------------------------------------------------------------------------------------------
              "Three-fourths of the Earth's surface is water, and one-fourth is land. It is quite clear that the good Lord intended us to spend triple the amount of time fishing as taking care of the lawn." ~Chuck Clark

              My New Bass Tracker

              Comment



              • #8
                Re: 87 Mercury Classic 50 won't throttle past 3000 RPM?

                Yep.

                I just went through my entire fuel system. Not sure if this is your problem but it solved mine.

                Search "Mercury TSB" in this section and find a posted TSB for "fuel starvation"

                Merc has a revised 'alcohol safe' fuel pump (for E10 gas) The valves are different. The revised pump's part # is 21-857005A1. It was 30 bucks at the dealer, I found mine on Ebay for 8.99 'buy it now'

                You also need an alcohol friendly prime bulb/hose. Old primers have shuttle valves which can come apart with the gas we use today. New ones have metal check balls and springs. The hose should have 'alcohol safe' printed on it.

                You should also use the silver tipped Merc inlet needles in the carb's. If your carbs were rebuilt with an aftermarket kit, the inlet needles could stick.

                *******

                After I replaced all that I still ended up with issues like you are having. The fuel line that runs to the fuel pump inside the engine compartment started to fall apart. I found debris from the hose in the carbs (AGAIN) so I took the fuel system apart (carbs included) replaced the fuel hose in the engine compartment, cleaned everything out again and found rubber pieces in my main jets and in the carb bowl.

                Once everything had a final cleaning, she ran like a raped ape.

                Its a pain in the butt but not expensive. The fuel hose was $3, fuel pump kit $10, inlet needles $8, fuel filter $10.

                Good luck

                Comment



                • #9
                  Re: 87 Mercury Classic 50 won't throttle past 3000 RPM?

                  do you guys think i might have a bad stator? i have a good outboard multimeter, i guess i could do some testing over the weekend. however, i don't want to test if this doesn't sound like a bad stator.

                  i'm planning on rebuilding the fuel pump and replacing fuel lines on friday. i'll let everyone know results. thanks, ac.
                  --------------------------------------------------------------------------------------------------------------
                  "Three-fourths of the Earth's surface is water, and one-fourth is land. It is quite clear that the good Lord intended us to spend triple the amount of time fishing as taking care of the lawn." ~Chuck Clark

                  My New Bass Tracker

                  Comment



                  • #10
                    Re: 87 Mercury Classic 50 won't throttle past 3000 RPM?

                    Don't get ahead of your self....replace the fuel parts first,and then post back with the results.

                    Comment



                    • #11
                      Re: 87 Mercury Classic 50 won't throttle past 3000 RPM?

                      I had the same problem on a 1982 50hp. Had the carbs apart a bunch of times except I never unscrewed the fuel nozzel inside the bowl. It had a little hunk of something in it that let enough gas in to idle and run at slower speeds, but then starved the engine when it really wanted to drink. Be sure to unscrew the brass fuel jet inside the bowl and make sure it is clear.

                      Comment



                      • #12
                        Re: 87 Mercury Classic 50 won't throttle past 3000 RPM?

                        This is similar to a problem I had with my 88 Merc Classic 50. I acquired the boat and motor from a friend for free, he told me it ran, but that the motor was underpowered for the boat...its a Tyee4.9 so I figured to myself that there was just something major wrong with the motor, since it only went 6 mph. Several things are like your problem......the first thing that we had done was the exhaust system was full of carbon from years of useage...I would look into that for sure. Next, after the carbon was out, it ran at 25 mph, for a month, then start to power down, and then kick in and run good, then power down.......that was the power pack, pretty easy to replace if you have any mechanical ability...just look at the old part and the new and compare as you go.
                        Hope that was helpful.....after replacing and cleaning those two things, the motor runs great. Could be carbs too, but we put in new kits and that didn't effect the motor at all.

                        Comment



                        • #13
                          Re: 87 Mercury Classic 50 won't throttle past 3000 RPM?

                          I just replaced the stator on mine yesterday.......but with the stator bad, it wouldn't start at all...I think if you are running still at 3000 it's not the stator.

                          Comment



                          • #14
                            Re: 87 Mercury Classic 50 won't throttle past 3000 RPM?

                            thanks cjames. i'll look into the exhaust. specifically, which part of the exhaust system needs the cleaning? one other thing...is the power pack the same as the switch box? thanks again, ac.
                            --------------------------------------------------------------------------------------------------------------
                            "Three-fourths of the Earth's surface is water, and one-fourth is land. It is quite clear that the good Lord intended us to spend triple the amount of time fishing as taking care of the lawn." ~Chuck Clark

                            My New Bass Tracker

                            Comment



                            • #15
                              Re: 87 Mercury Classic 50 won't throttle past 3000 RPM?

                              I finally fixed my classic 50
                              My motor wouldn’t tach up over 3000 RPMs
                              At first i had the ethanol blues,” so I cleaned my carbs, put in new fuel pump, new fuel cell, new lines
                              Motor ran good for about 10 min
                              Took everything apart 2 more times checking everything
                              Come to find out the 2 screws on my throttle actuator had stripped out, preventing full throttle
                              Mercury no longer makes the upper and lower throttle actuator, so I helicaled the screws,
                              Took a little bit to adjust throttle actuator, but I got it and it runs great
                              Be careful what you touch, I found out the hard way that 2 different problems produced the same 3000 RPM results

                              Comment

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