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1995 Merc 115 slowly loosing power

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  • 1995 Merc 115 slowly loosing power

    My 1995 Mercury 115 performed well for many years and really isn't performing too badly right now. It seems to be losing power. When new, it would get to 53 mph but the last few years it's dropped to 48 and now 45. It starts ok but will flood easily if you're not careful. The hole shot is decent but the throttle from 2/3 to full adds no additional speed, it just stays at 45 but seems to be using more gas.

    I took it to a Mercury mechanic but he said he couldn't find anything wrong. He took it to the lake and said it started and ran just fine. I'm surprised he didn't at least do a compression test. The motor is 20 years old but I go out on only about 3 trips a year, a week each. I use fuel stabilizer and the Mercury fuel treatment. The only other indicator is that at lows speeds it runs a little rough. I don't drain the carbs at the end of the season but I figure the stabilizer prevents varnish.

    My thinking is that it's the carbs, 1 or all 4, need new kits. It if were the power packs I think there would be more roughness, particularly at low speeds.

    Thoughts? Suggestions?

  • #2
    I was going to say compression test too but your comment nixed that idea. Let's start with a cheap solution. Go to WW or any auto parts store and buy about 3 red label/white colored pint cans of Sea Foam engine treatment. The can says mix 1 oz per gallon of gas or pre mix if you are a pre mixer but for your situation, I'd put the whole 16 oz to 6 gallons of gas. Go through the 3 cans, about $25 and come back on here with the results and we will take it from there. If my hunch is right that will be the end of it and then you can keep it in your fuel at the 1 oz per gallon rate and kiss problems goodbye. Now how do you suppose I know that? I learned it on here right after I first joined and by golly they were right. It works.
    Last edited by Texasmark; October 6th, 2015, 09:49 PM. Reason: Spelling
    If you are new to boating or have a new boat, a knowledgeable friend could show you how to operate your boat and save you a lot of grief, maybe some money, and maybe your life.

    Comment


    • #3
      I agree, I don't think it's compression. Although it's 20 years old, it's had very light use. When I was working I didn't have much time to take her out more than 2-3 times a season.

      I've been using the Mercury Quickleen treatment and I've not noticed any improvement. The red and white Sea Foam I see is Sea Foam SF-16 Motor Treatment, about $13. I'll order some and go fishing :-) Thanks for the tip.

      Comment


      • #4
        Originally posted by richw46 View Post
        I agree, I don't think it's compression. Although it's 20 years old, it's had very light use. When I was working I didn't have much time to take her out more than 2-3 times a season.

        I've been using the Mercury Quickleen treatment and I've not noticed any improvement. The red and white Sea Foam I see is Sea Foam SF-16 Motor Treatment, about $13. I'll order some and go fishing :-) Thanks for the tip.
        I figured your rings were all stove up and weren't sealing properly due to carbon and gummed up residual oil and maybe some varnish in the carb from the last fuel that was in it clogging your ports somewhat. SF will clean all that up over time.

        I don't know about the SF-16.....whether it's what I am referring to or not. $13 is way too much to pay for it. Course I only know of two of their products and the second is an aerosol which recently changed the label coloring and added some green highlights. Anyway it's worth a try.
        If you are new to boating or have a new boat, a knowledgeable friend could show you how to operate your boat and save you a lot of grief, maybe some money, and maybe your life.

        Comment


        • #5
          Originally posted by Texasmark View Post


          I don't know about the SF-16.....whether it's what I am referring to or not. $13 is way too much to pay for it. Course I only know of two of their products and the second is an aerosol which recently changed the label coloring and added some green highlights. Anyway it's worth a try.
          SF-16 is just the product code; Sea Foam 16 oz. They had the gallon size too. I checked at the Wal-Mart site and they were $13.03. The way you described it, red and white can, it sounds the same. The description on the can is similar to what you are describing and there isn't any other Sea Foam product like it at Amazon. Here's the link: http://www.amazon.com/gp/product/B00...ilpage_o00_s01
          .

          Comment


          • #6
            Yes it seems to be what I get. Don't order it, go to any auto parts store....Autozone, O'Reilly's carry it to name a couple I use. WW is the cheapest. These other guys get $8 and change.
            If you are new to boating or have a new boat, a knowledgeable friend could show you how to operate your boat and save you a lot of grief, maybe some money, and maybe your life.

            Comment


            • #7
              OK, two years have come and gone. I've been putting the Sea Foam in the fuel, but at the label rate of 1 oz. per gallon, not the full can in 6 gallons. I've gone through about 8 cans in the last 2 years. I don't see any difference in performance. It runs about the same as the last few years. It's a little difficult to get it started first time down at the lake, if it hasn't been started in a while. When I'm on a trip, first thing in the morning it needs to be cranked for about 5-12 seconds before starting. After that it starts right away nearly every time. However, after running close to full throttle for maybe 10-15 minutes, then slowing, sometimes it will stall and die. I've done Sea Foam and Mercury Quickleen mixed with Sta-bil (blue) most of last season. This season just Sea Foam at 1 oz. per gallon.

              Sometimes, first startup for the day, when I'm leaving the dock, at half to 3/4 throttle, it just lugs. It may do this for 10-15 seconds, then it kicks in and it's fine for the rest of the day. I checked the connections at the spark plugs and coils, no dirt or any buildup. Spark plugs look normal, all the same tan color. Factory dielectric grease is still inside the boots on the coils, not so much on the spark plug ends. Plugs were replaced this spring.

              Every time I take it to a Mercury mechanic it comes back with fewer bolts and screws. I really hate taking it anywhere, I feel like they really don't care. One time it had all but one of the carb baffle screws missing. I found them laying in the bottom of the cowling (after I had bought new ones). The last one just took it to the local lake and drove it around. I suspect he just went fishing in it. There was no entry on the repair ticket for any kind of bench testing. I guess I should be happy it's not getting any worse. Maybe I should just accept the performance loss. Shame, it used to be a speedy little boat.

              Comment


              • #8
                So far it appears no one has checked the compression, cleaned the carbs, made sure the timing is advancing correctly, ensured all cylinders have spark all the time, checked the fuel pump, etc.

                ​Start with all that and you'll most likely find the cause.

                Comment


                • #9
                  www.cdielectronics.com will have the guide to check your stator when it gets warm.

                  Comment


                  • #10
                    Originally posted by ondarvr View Post
                    So far it appears no one has checked the compression, cleaned the carbs, made sure the timing is advancing correctly, ensured all cylinders have spark all the time, checked the fuel pump, etc.

                    ​Start with all that and you'll most likely find the cause.
                    I've had it to 2 Authorized Mercury mechanics. They say it's OK. This motor is old but has had light use. The engine doesn't miss or run rough (although it will stall sometimes), it just seems to not have the power once did. I really suspect the carburetors but I'm reluctant to let any more ham-fisted Mercury mechanics touch it. Every time they do, they leave off more bolts.

                    Thanks for your reply. I think I'll just live with it. Maybe it will get worse, enough so that it makes it easier to diagnose.

                    [I found one more Mercury shop about 80 miles from me. They get good reviews on their diagnostics and repairs. I'll call them and see how long the wait is.]
                    Last edited by richw46; September 30th, 2017, 08:11 PM. Reason: Added more detail

                    Comment


                    • #11
                      You said they didn't check compression, they only said it ran OK, which it doesn't, and you said that you didn't trust them. Some of the issues that can cause it to run this way can lead to a destroyed motor, it's not hard to check all this stuff on your own.

                      Comment


                      • #12
                        Originally posted by ondarvr View Post
                        You said they didn't check compression, they only said it ran OK, which it doesn't, and you said that you didn't trust them. Some of the issues that can cause it to run this way can lead to a destroyed motor, it's not hard to check all this stuff on your own.
                        It runs OK in that it starts, idles and accelerates. When new it did 53 mph with just me and my gear. Now, with the same configuration, it does only 46. Other than the loss of speed, an occasional stall when I drop from plane to no wake speed (easily restarts) and slow early morning starts, it runs fine. Why the one mechanic just took it to a lake and ran it for a while I don't know. He said he didn't see anything wrong. That's why I think I'll take it elsewhere and let them do some analysis, like compression testing, check the coils and the switchbox. If all of those test OK then (I would think) it has to be the carbs.I don't have the necessary tools or technical manual which is why I'm hoping this next shop lives up to its reputation.

                        I used to have an old West Bend 9 that had a bad coil. It too started and ran OK, but when I put a timing light on it, one plug had a bright flash, the other was very dim. The motor sounded just fine, which could be what's happening with this Mercury; weak coil. I still have the timing light and water earmuffs for the motor. I can try the same test to see if one is weak.

                        Comment


                        • #13
                          If the carbs are dirty and don't allow it to reach peak RPMs and speed like before, then it can be running lean, which can destroy the motor (may have already). And since this is a 2+2 motor it will start fine if one or both of the two cylinders not used at an idle are damaged, but it won't put out full power at higher RPMs..

                          ​A compression test would be the first thing to do, bad compression means a rebuild, if you don't want to put that kind of money into it then you won't be wasting money checking other things.

                          ​You can borrow a comprssion tester from Autozone, or buy a cheap one, in 15 minutes you'll be able to have a plan for what needs to be done next.

                          Comment


                          • #14
                            OK, I will do a compression test on it, probably this week. It's a 4-cylinder, not 2. I found some advice on how to do the test. One of the steps is to ground the ignition wires to the block during the test. (also to use the water ear muffs). I'm assuming this is to prevent accidental starting, yes? I'll pull the kill switch instead. I found a decent tester on Amazon, it got pretty good reviews.

                            Comment


                            • #15
                              Sign up today
                              2+2 means that at an idle it only runs on 2 cylinders, at around 1800 RPMs the other 2 kick in.

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