Hydrolocked Engine

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mcarrigan

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Have a 5.7GS with OMC outdrive with carbs and electric fuel pump. Been having a stalling problem where the engine just seems to cut off. Doesn't sputter or anything. Almost like someone turned off the ignition. Starts right back up when cranked. Over the weekend it also ran for 3 or 4 seconds after the ignition was turned off. Took boat out and anchored on Tuesday and when I went to leave just heard a horrible grinding noise.

Got back to dock on one engine and figured out it was hydrolocked. Removed plugs, cranked it and seems to be running fine again except for the stalling. Couple questions, anything I should do since the engine had water in it or should it be fine if it's running without any noises? Any suggestions on figuring out the stalling issue or what caused the hydrolock. I read where the running after ignition is turned off can cause the hyrdolock.
 
If it "runs on" or "diesels" when you shut down, increases chances of sucking water into the heads via the exhaust. I know MerC uses Exhaust Flappers in an attempt to allow exhaust discharge OUT but no water back UP/IN. Volvo used to, but recommended removing them, and I don't know about OMC. Last hydrolocked Volvo I saw, was anchored stern facing a light chop and passing boat wakes.

Glad you're in Fresh Water, but still, what does the Oil look like? How old are your Manifolds and Risers? I'd at least change oil if I had the slightest thought water forced past the rings. Since water doesn't compress, and you tried to compress it with the starter, two worries come to the surface: 1. Could have blown the Head Gasket. 2. And this one's real but hard to believe. The torque of the Starter against a stuck engine can stretch the Starter Mounting Bolts. So get a socket wrench under there and make sure they're tight.

If it IS a failure in a Riser or Manifold, it's often at the Wet Joint where the two meet, and the water you find will be in a middle cylinder like 4, 6, 3 or 5.
 
The boat is a 98 and the manifolds and risers are original. Boat has always been in fresh water and only has about 650 hours. I checked the oil and it looked clean. I only ran the engine for about 5 minutes after getting rid of the water.
 
There are many with more experience than I have in this area. From what you're saying, if it was mine, I'd check the starter bolts. I'd run it a few times and inspect the dipstick AND inside the Valve Covers where the Filler Cap comes out. Carefully, looking for moisture. Pull the spark plugs and make sure they look clean enough, that you can tell if they get either gunked up, OR, very clean all of a sudden. Very clean could mean water getting vaporized by combustion and steam cleaning the piston top and head/valve/plug areas.

I'm lucky to get three seasons on a set of MerC manifolds here in our salt water. I know fresh water RWC V8's go a long time on an exhaust "set". That said, you're coming up on 20 seasons. Something other than the exhaust system may have caused this hydrolock. I still think, though, that the years you've got, are getting you to time-to-replace.
 
You dont tell us how you know it was hydro locked? Water out of plug holes? water in oil? some very clean plugs?
 
Lots of water out of one cylinder when spark plug removed. Quite a bit more came out as I cranked it.
 
Did you check the oil ? Any water ? You have very little time to save the engine once salt water gets in. 24 hours... 36 tops. A good way to do it is to pour diesel in the cylinders as it soaks in better than oil. If you had salt water in the oil drain it. Fill with diesel, crank... drain repeat and then with oil
 
Luckily (given the boat's actually in signature location) it's fresh water. There's a chance that a head is damaged. Chevy used "light weight" heads starting a number of years ago. Easier to rust through. We need Charlie to explain those heads.
 
Light weight heads can be id by by the bottom edge of the head, has a 'scalloped' edge. The heavy heads, 'straight bottom edge', went out about '74...but my memory ain't too good these days.

The grinding noise may be a tooth or two on the flywheel ring gear broke off. The ring gear is easy to replace but hard to get to.

intermittent starting is usually bad ground or connection to ground wire. Usually one of the heavy gauge black wires. Check ground wire at battery and follow it to the ground on the block. check that the starter bolts are tight as they are the ground for the starter. Check the red (batt) connection on the side of the starter but disconnect ground at batt first or you may get fireworks.

It's really pretty hard to get water from the cylinder past the rings. water in the oil usually comes from bad head gasket or cracked head but on occasion, water can get past a loose intake manifold bolt at the rear.
 
The oil looked fine so I don't think the water made it past the rings. If the water did get sucked in due to "dieseling" after the ignition was turned off and not due to a bad head gasket, do you think the engine is OK since water was only in there for a day? Still need to figure out what is causing the stalling and dieseling so I may have a mechanic take a look since I don't want this to happen again while I try to figure it out. Thanks for the info.
 
Well I ran if for a few minutes to in order to change the oil and it sounded fine. However the oil that came out had water in it. Changed the oil and ran it for a minute and could hear a ticking. Looks like it's time to call a mechanic. Now I'm thinking I blew a head gasket.
 
I'm afraid you're right, Blew Something... Hopefully a Gasket, but the mechanic that installed our "357" engine from MerC Reman (essentially a new 350/5.7) said the heads can rust through, near the valves.

If your 5.7 is "pre-vortec" replacing it with a Vortec Engine (essentially a pre-vortec with Vortec Heads and a different Intake Manifold) will be a step up in power. If your engine has a flat tappet cam, newer ones are roller cam, and again, a step up in power.

Since you say "OMC Outdrive" it seems to me you probably have Pre-Vortec with Flat Tappet Camshaft.
 
Do a compression test to see what cylinder is involved
 
It was cylinder 3 that all the water come rushing out of when I removed the spark plugs. At this point unless you think there is still a slim chance it's something minor I'm going to get a mechanic involved. With everyone's help I could probably figure out what's wrong but fixing it would be a different story.
 
Cylinders 03 and 05 are the two on that side of the engine, most likely to get water in them from a failure in the "wet joints" between Manifold and Elbow. Sometimes called Riser or Riser-Elbow. Our Sea Ray also has 3-inch Spacer Blocks, which double the number of wet joints. Any leakage "across" the sealing surface(s) allows water down into the discharge part of the Manifold, and Cylinders 3 and 5 (also 4 and 6 on the other side) are right under that part of the manifold. So those are the most likely to catch water first, from a leak in the wet joints or really any other part of the exhaust system.
 
I may have gotten lucky. Mechanic said he couldn't find anything wrong. I took it out and ran it for 20 minutes and it ran great. Still have to figure out why it hydrolocked in the first place but it doesn't appear to have caused any serious damage. I did experience it continue to run/sputter for about 3 seconds after the key was turned off at the dock. Could that cause water to be sucked in from the exhaust?
 
quote:
I did experience it continue to run/sputter for about 3 seconds after the key was turned off at the dock. Could that cause water to be sucked in from the exhaust?
Click to expand...


Yes! A "dieseling" gas engine can buck itself into reverse rotation. If that's what's going on, then the Exhaust becomes the Intake, and since the Exhaust is in Water, YES, you can pull water into the engine from the Exhaust.
 
quote:
Originally posted by j-d

quote:
I did experience it continue to run/sputter for about 3 seconds after the key was turned off at the dock. Could that cause water to be sucked in from the exhaust?
Click to expand...


Yes! A "dieseling" gas engine can buck itself into reverse rotation. If that's what's going on, then the Exhaust becomes the Intake, and since the Exhaust is in Water, YES, you can pull water into the engine from the Exhaust.

Click to expand...


And in that scenario, the water doesn't have to come from water at the exhaust outlet outside the boat, just from where where it was still being injected into the exhaust stream near the riser outlet to the hose.
 
You can lessen the chance of dieseling by de-carbing the cylinders ( i.e., SeaFoam or similar) to remove hot carbon deposits igniting residual fuel, and also clean the carb throat and make sure the throttle plate closes when engine is turned off. If idle speed screw is set to hold the plate open , likelihood of dieseling is much greater.

Since this type of ignition is not sequentially controlled by the distributor or in all cylinders, it's possible for the engine to actually run backwards momentarily. Not good in boats.
 
Thanks for the information Sandy and j-d. Have to figure out if this is related to the stalling issue which I'm pretty sure is electrical. Engine has never dieseled until recently.
 
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