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New to me LT1 with Fuel Dilution / Milky Oil

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  • #31
    Looking forward to your engine build.
    Attached Files

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    • #32
      Now for the fun part you will need to remove every all traces of that old head gasket and run a tap in each head bolt hole to remove the old thread sealant. In a perfect world you would brake the engine all the way down and inspect all of it. The LT1 has a strong lower end if it had good oil pressure and not making any noise I would do the head gaskets and let it bump.
      I would be more concerned as to why it over heated in the first place. I would replace the impeller and both of the thermostats on GP.

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      • #33
        In the process of cleaning and tapping tonight....what a PIA.

        Why it was overheating is also a question on my mind. When I went to check the thermostats, I found both missing and ordered the right ones. I'm wondering if the PO sucked up something and damaged the impeller....boat could have started to run hot so he pulled them both. Who knows. Tomorrow, I'm going to take a look at the impeller and check the trans cooler screens.

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        • #34
          I presume you are going to a machine shop for head work, etc. When you get the heads clean (really clean) ask the shop to do a dye penetrate test for cracks. Magnaflux test will not work on aluminum. I wouldn't put it back together without knowing there are no cracks, relying a non-destructive test, aside from a visual examination. Easy and inexpensive.

          .
          93 190
          (safe click)

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          • #35
            Originally posted by SeeJayGee View Post
            In the process of cleaning and tapping tonight....what a PIA.

            Why it was overheating is also a question on my mind. When I went to check the thermostats, I found both missing and ordered the right ones. I'm wondering if the PO sucked up something and damaged the impeller....boat could have started to run hot so he pulled them both. Who knows. Tomorrow, I'm going to take a look at the impeller and check the trans cooler screens.
            There is a cooling mod that is required for LT-1's. The t-stats and subsequent cooling components make up what appears to be a relatively temperamental cooling system, IE, really easy to overheat if the mod is not done. There is a sticky thread on this topic, where mastercraft made a service bulletin about it. It goes over drilling the appropriate t-stats and rerouting some plumbing that interfaces with the heads. If not done, you can experience aerated flow and excessive steam within the heads, causing the temp to spike.

            https://teamtalk.mastercraft.com/for...-system-issues

            This may have already been done on your boat, but just FYI. I'm not an expert on this or anything, but I was reading it as I just also bought an LT-1 205 and I do not think this mod was completed on my boat.

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            • #36
              Originally posted by Huckelfin View Post

              There is a cooling mod that is required for LT-1's. The t-stats and subsequent cooling components make up what appears to be a relatively temperamental cooling system, IE, really easy to overheat if the mod is not done. There is a sticky thread on this topic, where mastercraft made a service bulletin about it. It goes over drilling the appropriate t-stats and rerouting some plumbing that interfaces with the heads. If not done, you can experience aerated flow and excessive steam within the heads, causing the temp to spike.

              https://teamtalk.mastercraft.com/for...-system-issues

              This may have already been done on your boat, but just FYI. I'm not an expert on this or anything, but I was reading it as I just also bought an LT-1 205 and I do not think this mod was completed on my boat.
              At first glance, I'll need to make this update too.

              Congrats on the "new" boat!

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              • #37
                During the rebuild of my LT1 it also showed evidence of over heating after a full break down of the engine this is what I found was causing the problem. Over time small shards of old water pump impeller blades were plugging almost all of the 1/4 inch metering holes in the head gaskets. They also were plugging the steam pipe fittings. I had to remove all the freeze plugs to get to the ones that were wedged between the cylinders in the block. I think this is a LT1 problem due to the reverse cooling flow and the age of the engine. I am looking into some type of strainer could be placed on output of the sea water pump to stop this slow degrading of the water flow threw the engine.

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                • #38
                  new impeller every year should alleviate the issue going forward. You may want to do a leak down test after you get it all put together to make sure you don't have any more surprises later. GOod luck with your effort, summer may get here yet...

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                  • #39
                    Originally posted by curver900 View Post
                    new impeller every year should alleviate the issue going forward. You may want to do a leak down test after you get it all put together to make sure you don't have any more surprises later. GOod luck with your effort, summer may get here yet...
                    Agreed. I've always found this to be a good "peace of mind" practice. My 35-year-old two-stroke outboard hasn't complained either

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                    • #40
                      Random questions as I'm putting things back together:
                      1. Does anyone know the part numbers for the intake manifold bolts? Mine look a little rough.....
                      2. Should the stern side of the risers be connected to each other via hose or should there be plugs in there?
                      3. Any ideas on where to get cheaper exhaust hoses? Local shops are charging $30+ per foot locally
                      I always forget that taking things apart is the easy part and remembering how to put them back together is the hard part

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                      • #41
                        Originally posted by SeeJayGee View Post
                        Random questions as I'm putting things back together:
                        1. Does anyone know the part numbers for the intake manifold bolts? Mine look a little rough.....
                        2. Should the stern side of the risers be connected to each other via hose or should there be plugs in there?
                        3. Any ideas on where to get cheaper exhaust hoses? Local shops are charging $30+ per foot locally
                        I always forget that taking things apart is the easy part and remembering how to put them back together is the hard part
                        Manifold bolts standard bolts grade 5 or 8 match up the length to long may hit the push rods. Use thread sealant on the bolts.
                        The front 3/4 npt holes connect to 140 thermostat housing in front. The rear 3/4 npt holes (3/4 nylon pipe plug Indmar # 605051 Inboard on line) could also be hooked together with a drain coupling.
                        Exhaust hose Try Shields 200 Go2Marine
                        You should also replace the Riser gaskets (2ea Indmar Riser Hardware and Gasket Kit $4.43 Inboard on line)

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                        • #42
                          Wanted to give an update.....

                          Got things back together and used the heads being off as an opportunity to flip them around to make the cooling fix a bit easier. The engine seems to be running good, but I don't like how hot it's running on the hose. This evening it hit 180 on the temp gauge despite new thermostats. Tmrw, I'll be back flushing the trans cooler (again), replacing the impeller (finally) and depending on how that goes, I'm planning to put the thermostats in the wife's sous vide to ensure they're opening at the right temp.

                          Any other suggestions on the cooling situation. Part of me wants to think that the Fake A Lake just isn't flowing enough water to properly cool....but it shouldn't be hitting 180.

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                          • #43
                            I did a lot of testing on my LT! when I was running it on my test stand after I rebuilt it. Water flow is critical to keep this engine cool. I was pulling the cooling water out of a 5 gallon bucket with the water hose keeping it filled I found at idle the hose could produce more than needed. At 1000 rpm the engine was taking more water than the hose could provide and the water level in the bucket would start dropping. I am not a big fan of the fake a lake. Indmar makes a strainer with a hose connection that works a lot better protects the system from fod.
                            The places to look for restrictions trans cooler I would take the water lines off and do a visual with a light shining threw from the other end should be able to see right threw it.
                            The rise gaskets this is the choke point for water flow in the exhaust the ports need to be clear.
                            The sea water pump not only does the impeller wear out but over tine the housing and cover tend to wear.
                            Thermostats best way to test them is in a pan of water on the stove with a digital cooking thermometer you can see them open and close. You can also test all three of the temp sensors this way with a ohm meter attached to them.

                            The circulation pump what can go wrong here it is driven off the cam shaft if it has locked up it will shear the coupling in side and it might not be turning. The impeller in this pump can also wear out over time they can become crowded and wear down.
                            Last edited by RDahler; 05-15-2022, 10:15 AM.

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                            • #44
                              Sounds like numerous design issues with this powerplant. Glad I don't have one.

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                              • #45
                                Spent some more time wrenching on things this evening and ran the boat on a hose with a bucket. On the first run, the temp crept up steadily to 180. After a shutdown and impeller swap, the temp climbed again to 180 but then started falling back down after giving it some gas. Positive progress!!

                                I suspect it's just not getting enough water to cool itself and am going to try a lake test this week to confirm.

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