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Hydro-lock, Cylinders full of water-gctid383890

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    Hydro-lock, Cylinders full of water-gctid383890

    Well guys I have a question. All the threads on here containing info on Hydro-lock seams to be from the engine overheating, cracked heads or blown gaskets. I was idleing away from shore ramping up speed and trimming the tilt down at the same time when the boat stumbled and sputtered and died. With the radio on and everything else going on I didn't really hear what it sounded like, but the result ended with the engine full of water. IMO I believe the engine is pretty sound and ussually runs pretty good. I did have my mech. take the gear case off this spring and lube it up for maintenance. He believes that when it stumbled and died it diesled , ran backwards and sucked the water from the risers into the cylinders. I guess I can understand that. My question is, is there anything from reassembling the gear case like a gasket out of place or not sealed that might of had a hand in this? I'm trying to think of everything to keep it from happening again. I got the water out went through two oil changes and it ran just fine for about 30 minutes at the pier. But I have to say, I will be a little nervouse going out the next time without any insight on what might of happened.

    Thanks for any input.


    A SBC 5.7L does not typically diesel unless it has been very hot. If it did become hot and diesel, and were to reverse direction, you will have pulled water in against hot valves. This where damage may occur in addition to the Hydro-Locking.

    You'll want to do some extensive testing, IMO.

    Rick E. (aka RicardoMarine) Gresham, Oregon
    2850 Bounty Sedan Flybridge model
    Twin 280 HP 5.7's w/ Closed Cooling
    Volvo Penta DuoProp Drives
    Kohler 4 CZ Gen Set

    Please, no PMs. Ask your questions on forum.


      I'd say there are some much more obvious areas that a water ingestion would have happened than just idling along too. If it died, and was hydro-locked at idle, I'd be looking at that cooling loop first. There are lots of ways for water to get in. Riser inspection would be where I'd start.

      Is the motor raw water cooled?
      Custom CNC Design And Dash Panels


      1980 CHB Europa 42 Trawler- "Honey Badger"


        In answer to your original question about the work on the gear case, I would say generally no, there is nothing done down there that would result in water ingestion to the upper engine. The reasoning on dieseling sounds plausible as you were at low RPM and the boat stumbled. I presume you have a dist and not elec ignition?

        If you have all the water out now, I think you should run a compression test, and maybe a leakdown test to insure you have no bent valve, or leaky head gaskets.


          Your boat is an 87. Is it still powered with an OMC?

          I had the exact same issue several years ago. The boat stumbled and died. The resulting back wash, as the boat came to a stop, caused water to get past a stuck flapper. The result was hydro lock on the port side.

          The flapper is in the exhaust system just down stream from the riser. It's a rubber coated plate that is supposed to close and prevent a back wash. Mine was stuck open.

          Hope this helps.



            I do agree I have a feeling theres more going on here than meets the eye here. I am going to do a compression test. What other testing might I do or have done? I really don't believe the engine deisled when it stalled but I'm not sure, and since there was water in both banks I can't believe both heads are cracked or would leak in water for as well as it does run, but who knows. I guess we'll be testing what ever I can think of testing. We'll let you know. I have this skiff remodled better than new consmetically, I guess it's time to work on the engine.


              The easiest test would be to pull the bellows on th "Y" pipe and check the flapper on the side that hydro locked. I had the same thing happen 3 years ago but it started as an over heating problem at idle and took me 2 years to track down.

              300SD all options sold.


                Well, I would really like to find a cause to the hydro-lock situation. I hate to think it was a freak thing that just happened. I'm not sure where the flappers are, I see many, diagrams of the water route and such in the manual but it doesn't show where the flappers are actually located. I did a compression test tonight, ran the boat for 15 minutes and the temp never exceded 170. The port side riser was a bit cooler than the starboard side but I could still rest my hand on either for a while. The results of the test were -

                170 170

                170 160

                160 165

                170 170

                from what I read these aren't bad numbers, but if any one has any other advise on any other tests please let me know. It's time to get this thing right.

                I've done a ton of resurch on here and am overwhelmed with info.

                Thanks to all,



                  Do you have "log style" manifolds with risers on the ends or the center style manifolds and risers?


                    Mine hydro locked 2 years ago and it was not hot. Bad fuel caused it to diesel. Pumped the water out and has had 100 hrs put on it since. I did break a tooth of the ring gear and some of you know what that means(motor out to fix a $20.00 part. Keep an eye on it.



                      I believe my risers are on the end towards the rear, not in the middle.

                      I can believe if it diesled, it could be water in the gas. How do i check that and pump it out as you say you did? I put a new filter on as well, but every spring I question the gas quality.


                        I think the old log style manifolds and risers are much more susceptible to ingesting water caused by a variety of situations. If you were just getting up on plane, the stern of the boat was deep in the water. A quick stop might drive water back in, regardless of the flappers, and especially if the engine was still turning, even if just for a second.. Those cylinders are acting like a reverse. I screwed up my first engine in a similar way. An ignition wire came off the key switch when I was running at cruise speed, came to a sudden stop, and I had water ingestion in #8 that broke one lifter rod and bent the $hit out of the other. I know that when I replaced that engine with the Vortec, I had water ingestion twice, both times my fault. The old engine had a Rochester carb on it which required 4 pumps on the throttle to start. The new Holley was a different story. I was at the slip and went to start the new engine with 4 pumps. It turned over and backfired, which sucked water into the cylinders. That carb takes two pumps, and two only! I screwed up another time starting it in a similar fashion, and I have been extremely careful starting ever since with no further problems. The place we hang out at in the summer has a lot of heavy boat traffic going by during the day, and many times my boat has been stern-to the wakes. In this case, the flappers always seemed to have worked properly with no water intrusion as the engine was not turning. Just my observations and expensive lessons! You have good compression, so it's likely you're ok, however take it out and see if you can get WOT out of it. Let us know what happened. I don't think water in the gas would cause dieseling, but timing/an ignition problem would. Be sure to check/have that checked.