5.7 mercruiser water ontop piston - Boating Forum

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5.7 mercruiser water ontop piston

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  • 5.7 mercruiser water ontop piston

    hey everyone! I have a 1998 25 foot cruiser with a 5.7 mercruiser, the other day went for a sail everything was fine, the next day went to start the boat and it was hydrolocked, pulled all the plugs out and the first cylinder on the right side of the engine had water, but not water in the oil, i took it out for a sail it ran fine i could shut the engine for a couple minutes and it would start right back up no problems, when I came in I drained the block and went home, next day came back engine started fine went out for the day but this time if I shut the engine down for even 10 seconds it would lock up but if I held the key it would eventually turn over and start, did this a couple times as it stalled a couple times while I was out, just from changing gears, (always had a habit of that) but now it seemed as tho the cylinder was filling quicker, what I have noticed is that is it always the number 1 cylinder filling up, i took the boat home drained the block and ran fresh water threw it and once again it locked up as soon as i shut if off and now I have water in the oil (probably from when I held the key and forced the water passed the piston) I took the high-riser off and it looks perfectly fine inside, doesnt seem to be much rust if any, but the manifold has water sitting in the bottom of it, also the manifold was still full of water in the cooling jackets when I took the high riser off the water was flush with the top of the manifold, now if the manifold was gone wouldnt of this water have run into that number one cyl? Seems to not lock up when I drain the block, it sounds more like a head gasket gone to me now that I know the manifold was holding water and after draining the block and cyl the motor would turn over just fine after sitting for a couple days, but if its the head gasket how did water get to lay in the bottom of the manifold on the exhaust side of it? Seems strange that it is always and only the number one cyl... could this more then likely be a head gasket? The spark plug seems to be a normal colour when I pull it out so it doesn't seem like its burning salt water while its running? Any help would be appreciated thanks everyone!!

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