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Johnson 140TL Burnt Piston?

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  • Johnson 140TL Burnt Piston?

    Hi everyone,
    I purchased a boat today with a Johnson 140TL on it. The PO told me that his brother went out on it about 6 months ago, and didnt charge the batteries. Said he ran it and it started skipping real bad. Managed to get to the dock and trailer the boat. He then says he took it to a marine mechanic that told him that he had a burned piston and it would have to be rebuilt. He told him that it would be cheaper to buy another motor. He sold me the boat and motor for 2000 dollars. I figured I could part out the motor if I had to and the boat was worth more than I paid for all of it. So I decided to take a look at the pistons to see how bad they are. I do not know enough to determine, but they move freely and look ok to me. The cyc look clean, and have oil on them. I rubbed each of them and didnt notice any scars at all. What I did find that looked weird was both of the fuel pumps looked melted. I also noticed that one of the coil packs was broken. PO also said that there was low compression in one of the cyc. I will be getting a compression tester tomorrow. This motor is the VRO. I am not that versed in these type motors. Please take a look at these pics and tell me what you think, and what would do this to the fuel pumps.
    https://plus.google.com/photos/11762...Pif1suy__e69QE

  • #2
    Re: Johnson 140TL Burnt Piston?

    Those aren't the fuel pumps as they are the theromostats and are bad. Also looks like you have a scuffed cyl. Would recommend an OEM Factory Service Manual. Lots of info if you plan on doing your own work.

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    • #3
      Re: Johnson 140TL Burnt Piston?

      Thermostats huh. Well I wasnt sure to begin with to be honest. The rubber gasket threw me off. What would make the melt like that though? Also with a scuffed cyl what is the best way to handle that? That would explain the low compression stated by PO I would think. I am thinking that VRO thing didnt work for some reason and he ran it without oil in the gas. I am going to remove the vro part. I dont want that to happen to me. So you for sure do not see a burnt piston right?

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      • #4
        Re: Johnson 140TL Burnt Piston?

        If the VRO was bad it would have damaged all the cyl's. A lean running carb could scuff a cyl. Was this mtr run in salt water???

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        • #5
          Re: Johnson 140TL Burnt Piston?

          No the motor and boat were purchased in Seneca SC, and I live in Easley SC. Mostly run on Hartwell Lake. I looked on this site for thermostats last night, but could only find gaskets. The gaskets I found didnt seem to match up to the ones in the pic I took. I kinda thought the same thing about the VRO not working myself. I think I see the scuff mark you are talking about. It isnt deep. I ran my finger across it. Is there a way to fix it without taking out the piston?

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          • #6
            Re: Johnson 140TL Burnt Piston?

            Originally posted by dadtodc View Post
            No the motor and boat were purchased in Seneca SC, and I live in Easley SC. Mostly run on Hartwell Lake. I looked on this site for thermostats last night, but could only find gaskets. The gaskets I found didnt seem to match up to the ones in the pic I took. I kinda thought the same thing about the VRO not working myself. I think I see the scuff mark you are talking about. It isnt deep. I ran my finger across it. Is there a way to fix it without taking out the piston?
            i just bought a boat from seneca sc its clemson colored lol good luck on ur problem

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            • #7
              Re: Johnson 140TL Burnt Piston?

              I think it's safe to say it overheated bad if the thermostats melted. That accounts for your scored up cylinder. Let's see what the compression is on all 4 before you decide what you want to do with it. Running the motor through muck and sand could have clogged up water passages, although what we can see in the pics look quite clean, or it could have a worn out water pump impeller (which is in the lower unit). To be on the safe it is common to replace the $20 or so rubber impeller every season or two but some time on this forum turns up a lot of people who don't.

              All of that rust on the surfaces of the cylinder sleeves is going to be a clue. Either the head gaskets were loose and/or battered, or overheating warped everything out of line and the gaskets stopped gasketing.

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              • #8
                Re: Johnson 140TL Burnt Piston?

                Ok, thanks a ton! I will report back with the compression test asap.

                Comment


                • #9
                  Re: Johnson 140TL Burnt Piston?

                  Okay,
                  So I tried to do a compression test. I must not be doing it right. This is the first time I have ever done one. I took all plugs out and borrowed a compression tester from a local autoparts store. Let me start by saying that i took the heads off yesterday as you all know, and there are no thermostats in the heads because I took them out. So back to the compression test! I couldnt even get the needle to move on the gauge. Not one cyl. So I am guessing that since I took the heads off, and put back with the same gaskets is why. Or maybe because the thermostats are out. Or maybe Im a freaking idiot and cant seem to do this simple task. I did check that scuff out once more, and it definately looks scuffed in one cyl. I scrapped my fingernail across all and it doesnt snag my nail, but I can feel the grooves . Is there a way to fix this ?

                  Comment


                  • #10
                    Re: Johnson 140TL Burnt Piston?

                    I did check that scuff out once more, and it definately looks scuffed in one cyl. I scrapped my fingernail across all and it doesnt snag my nail, but I can feel the grooves . Is there a way to fix this ?
                    That cylinder needs to be bored... A common problem with the small bore 120/140 loopers as it has a bridged port exhaust, and when they get hot the bridge expands and pinches side of piston which may be what happened here. Tear it down and fix it correctly before it gauds up and causes more damage..
                    When in doubt,Trim it out!!!
                    Business Owner & Certifed Technician
                    Boats I own & use
                    20ft Javlin w/250 Junkrude
                    17ft Bullet w/200 Merc (SOLD!!)
                    13ft Allison w/150 I-6
                    17ft Hydra-Sport 175GT
                    15ft Allison w/75 Stinger(project)
                    14 x 48 Drifter with 1100SS Merc

                    Comment


                    • #11
                      Re: Johnson 140TL Burnt Piston?

                      OK thanks for your time assessing this. When you say bore you mean with a honing tool right. That means just replacing rings right. I am fairly handy with most anything. I read this forum a lot and have learned a tremendouse amount. I searched last night on here until around 2am for his to on sound this. Hard to find specific things sometimes.

                      Comment


                      • #12
                        Re: Johnson 140TL Burnt Piston?

                        First of all I would like to thank each of you for the comments. I do not post often, but I read this forum daily. I love to learn this stuff. I will be attempting to dissasembel my motor today. I call a local marine shop that I have done business with in the pass, and we have become friends. He says if I take apart and bring in just the block that he will help me hone it myself. Also I have instructed him to go ahead and order me 2 head gaskets, 1 ring, 2 thermostats, and and impeller. I have been reading a tn of threads on this since it has been suggested. Trying to find pics, videos, or any other alternative. I have found a few, but none that fit my needs. I am handy, and mechanically inclined, but very nervous to take this apart. I really dont know where to start. I know I need a manual. I was hoping to find a breakdown on here with pics for reference. I have looked at the pics, and cyl a number of times and just think it isnt that bad. hahaha I know it has to be fixed though. I will be rebuilding carbs as well. If anyone has any other advice please share it with me. I am open to any other suggestions...

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                        • #13
                          Re: Johnson 140TL Burnt Piston?

                          Okay everyone. I called the local Marine Mechanic and talked to him more in depth about the cylinder. He seems to think we can hone the one cylinder without taking out the pistons. I have searched this forum as well as the web for any mention of this. Is this possible with what I have? He says that we can try this, and it will get the boat to a point to get in the water. He says it will either fix it or give it legs until after the boating season, then if it just gets worst we can then tear down and bore. he says it will not cost much more than taking apart and honing. Any thoughts on this?

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                          • #14
                            Re: Johnson 140TL Burnt Piston?

                            I called the local Marine Mechanic and talked to him more in depth about the cylinder. He seems to think we can hone the one cylinder without taking out the pistons.
                            You need to find someone else in my opinion... There is damage all the way down the side of the piston and rings not just what you see. That cylinder wall if it has grooves will need to be bored oversize,you cannot hone one oversize..(only in a Sunnen machine) You already have aluminum transfer from piston to cylinder wall so compression will be low in that cylinder and it will keep transferring until it locks up or throws a rod depending on rpm.
                            When in doubt,Trim it out!!!
                            Business Owner & Certifed Technician
                            Boats I own & use
                            20ft Javlin w/250 Junkrude
                            17ft Bullet w/200 Merc (SOLD!!)
                            13ft Allison w/150 I-6
                            17ft Hydra-Sport 175GT
                            15ft Allison w/75 Stinger(project)
                            14 x 48 Drifter with 1100SS Merc

                            Comment


                            • #15
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                              Re: Johnson 140TL Burnt Piston?

                              I have decided to go ahead and sleeve the cylinder. I took it to a friend of mine that does this , and owns a marine shop. He has quit doing service work and focuses mainly on sales now. He buys and redoes boats and sells for a profit. I took the whole boat by his place and he says that he would suggest sleeving the bad cylinder, and re-ringing the rest. Also replacing bearings, wrist pins, and all that good internal stuff. He says he doesnt half *** anything. He is going to do it all for 500 dollars with my labor. he says if I breakdown the motor and bring him just the block he will take it and have it sleeved and bored back to factory then hone all cylinders to .20 . Then he will help me reassemble the motor back together and set all the stuff back. I think 500 is a great deal. Any thoughts? Anyone have a guide to breaking down the engine? Thanks for looking!

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