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Need To Fill Corroded Block-to-Head Mating Surfaces on 97 Yam 150 2-stroke

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  • Need To Fill Corroded Block-to-Head Mating Surfaces on 97 Yam 150 2-stroke

    Hello everyone!

    I've got a 97 150hp 2-stroke (S150TXRV) that I've owned since 2004, and it has always been used in a salt-water environment. I personally rebuilt it in 2006 after a 1/8 - 1/4 in hole formed in the block and leaked water on the lower starboard rod-crank bearing, and over time it disintegrated. At the time of rebuild I had a marine mechanic weld the hole, and another area which I believe was the center area of the exhaust on the block mating surface to exhaust cover. I also removed all corrosion and painted the internal surfaces with Rustoleum Rusty Metal Primer. Whether that was a good decision or not I don't know but the motor has lasted this long (400 hours & 13 years since rebuild). All the details of that rebuild are here for anyone interested:

    There's been a variety of maintenance in between.

    Fast forward to present: I am out boating last Saturday, and the motor ran good until I noticed it would no longer keep and idle and keep huffing and puffing (missing).
    I get home, did some troubleshooting, and ended up pulling the port head, and a 3/16 hole was present in the top port head. Wow - I didn't know that could happen:

    I pulled the water jacket off the port head and it was just a mess inside.

    I had pulled the port head a couple times before to clean the passages (just the head-to-block side; shame on me for never pulling the waterjacket in 13 years since the rebuild) due to overheating on the port side. I pulled the starboard head and associated water jacket and it was a mess in there also.

    Here's the part I have a question about: I noticed some corrosion near and into the mating surface on the upper part of the block:
    Picture5: rt.jpg

    I obviously need to fill in these areas. I know that I can likely have a welder come out to my location (boat is on a lift and I do not have a trailer) which will be probably expensive in labor. I also heard that aluminum welding is difficult. I don't know anything about welding. Is a viable alternative to welding to use some sort of epoxy to fill these areas and smooth out by sanding?

    I don't know how much life I have left in this block. I hope it is alot. I am already planning to buy NEW heads at around $280 each, as there are a bunch of used ones on ebay around $100 each but they all have waterjackets on them, and I could be buying the same corroded thing. I want to do a good repair but I also don't want to throw a ton of money into it only to discover 6 months down the road the block is leaking again inside or etc. which would require a repair/build of the powerhead again.

    Is there a special epoxy that can be used? I've looked at:
    Loctite Metal/Concrete Epoxy (apparently not for constantly wet areas)
    JB Weld - Marine Weld

    What do you all suggest - is epoxy a viable solution that will last a few or more years?

    Thank you much for helping me get started on my repair.

    Thank you much.

  • #2
    I have a correction to make to the above post. The link for Picture 5 is incorrect and duplicated with Picture 4.
    Picture 5 is supposed to be this:



    • #3
      if you refuse to take apart and have it welded up and machined back down flat, then clean really well and try some JB marine and cross you fingers.
      see how long it lasts.

      fixing a hole that is completely thru already I would not trust, but only a divot should hold .

      but that is just my opinion, and you should know how much that is worth


      • #4
        When doing such things as you purpose it is hard for anybody to give advice on how long it will last, that's the chance you will have to take.

        It looks like your heads got the worst of it for sure. But if you are going to give it a go with the block i have few suggestions.

        First thing is to get rid of the surface corrosion and see how much pitting you will have to fill. You need a good flat tool that you can attach some adhesive backed sandpaper to. An appropriate size piece of aluminum 6061 T6 sheet say 1/2" thick would work. It needs to be almost the length and width of the surface you want to rework. It needs to be flat, like glass flat. But again what you use is up to you.

        Next you need to grind out the pits with a die grinder and a burr to remove all corroded material... back to clean aluminum.

        Clean it several times with acetone, with white cotton rags, it needs to be super clean.

        Overfill all pits and let whatever epoxy filler you chose cure completely. Knock off the high spots with a smooth file and then back to sanding it with your homemade cylinder block resurfacing tool. If you still have low spots, rough them up with some sandpaper, clean again and add more filler. Repeat until you have everything flat.

        JB weld makes high temp epoxy filler..I would use that.

        Will it hold and how long will it last...I don't know.

        Good Luck and send some pictures of your progress.


        • #5
          Thank you 99yam40 and Panasonic for your very informative responses. You give me hope!

          Panasonic, I looked for high temp JB Weld on this page:
          but I don't see anything advertising high temp. I fall back to JB Marine weld:
          though it does not indicate temp. What do you think?

          I understand what you are suggesting - use the sandpaper on an absolutely flat block to sand down the high areas of the expoy on the mating surface; what grain sandpaper do you recommend, and just curious - will the sandpaper potentially remove some aluminum if I am not careful? Are you suggesting that the flat block I use should be a little bigger than the head mating surface as to evenly sand the entire surface, or can it be small to just cover and overlap the area that i am filling which isn't very big - Maybe a flat block a couple inches by a couple inches would be appropriate?

          For clarity, I am reposting what I posted earlier (without the errant picture). These are the two areas on the block side I must fill:
          Picture 5:
          Picture 6

          Thank you all so much for your advice. I appreciate it.


          • #6
            OK I guess my response has to be approved. I'll wait!!


            • #7
              Google jb weld high heat or extreme heat. Regular JB can stand 500F degrees or something like that.

              Can you post a picture of the whole mating surface of the block?
              Approximately how big is that surface...length x width?
              Is there more pits then you show in those pictures?


              • #8
                I found the JB weld high temp epoxy filler:
                Do I really need high temp to 2400F? I mean I'm thinking the block conceivably might be 300-500F, or not even - the seawater passes right through this area. It mentions nothing of water immersion. Not really sure here.

                Here are the whole mating surfaces of the block:
                Picture 7 Port Mating Surface:
                Picture 8: Starboard Mating Surface:

                I don't see anymore pits than the top part around the thermostat area. I think I am a bit lucky in that regard...


                • #9
                  I'd clean everything up real good as they corrosion usually goes deeper than what the eye can see.

                  Especially with the welder coming, you wan him to fill critical spots...

                  Once he's set up, moving from one crevice to another isn't a big deal.

                  SUPER cleanliness is the key.

                  There was a thread about soaking the head, etc in a chemical (forgot what it was-someone may know), but it worked very well.

                  *My neighbor gave me an old mercury 6 cylinder decades ago with a 1/4 hole between the combustion chamber and water jacket (no separate cylinder head).
                  I cleaned out the hole (now 3/4" at the widest point), made a custom aluminum plug and had it welded back in there. I couldn't access the INSIDE of the combustion chamber W/O a complete tear down (and didn't). Motor ran good after that, bought another hull and sold em..
                  1997 Angler 204, Center Console powered by a 2006 Yamaha F150TXR


                  • #10
                    Maybe time to consider new/newer motor?....that corrosion may just keep returning...


                    • #11
                      Yeah I am not ready to drop that kind of money. I want to make this run longer.

                      I wonder if anyone ever tried to do this with epoxy as opposed to welding, and been successful...


                      • #12
                        Good pictures.
                        This is an example of how corrosion "takes off".
                        In a new engine all the surfaces would have been "factory painted" upon fresh clean new aluminium. It would take some time for this surface to be breached by corrosion. The problem then arises as what to do when the corroded part has been cleaned away. It has been often mentioned that meticulous cleaning followed by a quality zinc chromate paint application should always be done, and then be mindful that this will not last as long as the original I.e. you now have a liability to maintain that "injury", so shorter inspection times are needed.
                        This is now a problem as aluminium is porous and corrosion goes deep and weakens the structure (as we see before us). From the pictures it is obvious this motor had been apart before and cleaned etc.; exponential corrosion thus followed. One good point though is the bolts were able to be removed at this time without breakages.
                        Now you are going to replace the heads and waterjackets, they are beyond repair. If you are purchasing secondhand you are obviously going to have the waterjackets removed.
                        Looking at the block, the passages around the cylinders are remarkably clean. For that reason I would invest in getting it welded properly. This will at least provide hard structure; although considerable porousity may still remain. If you were to use JB Weld definitely go for the highest temperature, may seem not needed, but higher temperature resistance may suggest a more stronger or durable product.
                        Extreme cleaning, as suggested, and proper "painting" of surfaces in contact with water is essential, you may look into that separately if using second hand parts.


                        • #13
                          Up to you on the JB weld, I would go for the high heat to be on the safe side.

                          "Are you suggesting that the flat block I use should be a little bigger than the head mating surface as to evenly sand the entire surface, or can it be small to just cover and overlap the area that i am filling which isn't very big"

                          hat I am suggesting is to lightly abrade the "whole" surface to clean up all the surface corrosion now that you have it apart and keep it as flat as possible. Then fill the voids, knock down the high spots with a file or small sanding block till almost flush with the surrounding good surface THEN using the larger sanding tool to finish.

                          To keep the surface flat you need a large flat plate of some sort, I would have it at least as wide and maybe half the length or more of the block and take long strokes from one end to the other. 220 then 400 sandpaper would be fine. You will remove very, very little material.

                          Think of it this way. On a smaller engines it is easy, say a 9.9 HP the cylinder head is small enough that if it needs to be flattened because it warped, you can glue sandpaper to a known flat surface (that is bigger the head) and sand it back flat by moving the head on the stationary plate. You can even do the block this way. Its right in the service manual for your engine for the cylinder head.

                          Now that is not possible for you situation as the block is still assembled, and it is too big, so a good size flat plate will have to do and not so big that you cant handle it properly.

                          You are putting "new" heads on this block so I would take the time and do this repair as carefully as possible and hope that your results will be sufficient. As already mentioned the proper way would be to remove the block, have it welded and machined back perfectly flat. They would take a skim off the whole surface.

                          You luckily still have original material left at the worst spot, the corrosion did not bridge right across.

                          You need to address how to keep those cylinder bores clean from the debris you are going to create as well... Block.jpg


                          • #14
                            Bigger picture....

                            block 2.jpg


                            • #15
                              I am very grateful for each of your informative responses Zenoahphobic, Panasonic, Townsends, Robert.

                              Zenoahphobic- Thank you for that explanation regarding paint protection & corrosion. Back in '06 when I rebuilt it I painted all water passage surfaces with brown Rustoleum Rusty Metal Primer (good or bad, right or wrong but certainly not zinc based as you mentioned.). I still see that primer in some places; I guess it helped to "some" degree.

                              Panasonic - Thank you for the explanation of preparing the block mating surface. I can clearly visualize what you have taken the time to explain.

                              These pictures are after I took the wirebrush, vacuum cleaner, and compressed air to each of the areas surrounding the cylinder bores. Even though before the cleaning, they weren't all that bad. The heads were much worse. It seems much of the gook accumulates in the heads and waterjackets, vs. the block. This is also after I wirebrushed the mating surfaces.

                              I will keep much of the debris from the cylinder bore ports using wadded up papertowel, depending on piston stroke, and will use a vacuum afterward.

                              You've convinced me on the high-temp JB weld if I go with epoxy.

                              I'll see if my old marine welder from '06 is still around and willing to come onsite for a reasonable charge, but I'm not too optimistic about that.

                              I see that in my first post there was a broken link that referenced my 2006 rebuild of this powerhead.
                              Here is the correct unbroken link for reference:

                              How do my sacrificial anodes look? As I recall they looked similar when I installed them in 2006, that is to say they currently look hardly sacrificed.