Merc keeps hydrolocking

[jdubslopro]

Ok, normally I would attribute this problem to a bad riser gasket/bad manifold. But I've pulled them both and doesn't look like there's any water getting past the gaskets. But for some reason ALL the cylinders get water in them. Oil is clear. Pull the plugs, clear the water out, starts and runs fine, doesn't get any more water in there.
I just started having this problem in the past month, every time I ran the motor before it hasn't locked up. It has done this on 4 occasions out of the last 6 times running it. It's usually after it sits for a day or two. It happened once when in the water, and the rest of the times it's happened on the hose.

Engine is a rebuilt 5.7 mpi mated to Alpha one raw water cooled, standard manifolds and elbows (no additional risers). Water temp is consistent 160* on the gauge when it's up to temp, oil pressure is ~40 at idle.

The first time it happened was when dropping it into the water, so I assumed that my issue was from dropping it in too quickly and water was forced through the drive into the manifolds and into the cylinders, but now it's also doing it on the hose.

 

[Bt Doctur]

Re: Merc keeps hydrolocking

Sounds like leaking manifolds. drain everything, pull the risers, fill manifold up to riser joint and wait. You will see water droplets begin to from at the bottom. lookin down the exaust port.look near the casting rib. might take a few minutes but they will appear.

 

[jdubslopro]

Re: Merc keeps hydrolocking

Thanks for the advice. I was considering draining the manifolds next time I run it, and if it continues to hydrolock then it probably isn't manifolds. Yours seems like a better way to see for sure.

 

[tpenfield]

Re: Merc keeps hydrolocking

Intake manifold would be worth a check.

 

[jdubslopro]

Re: Merc keeps hydrolocking

Intake looked good (just pulled the motor last week and put in a new head gasket) sealed it all up and put it back together. I'm on my way outside to double-check the manifolds.

 

[Don S]

Re: Merc keeps hydrolocking

Not the manifolds where they go on the head. The gaskets between the manifold and the elbow is your problem. Or the manifolds, elbows themselves.

 

[jdubslopro]

Re: Merc keeps hydrolocking

I did as Bt Doctur advised and it appeared as though there were water droplets forming in the walls of the manifold. There is a possibility that it had just spilled over the edge from filling the manifold, but I'm just going to replace the entire manifold/riser assemblies. Usually a bad intake mani/gasket will leak water into the oil, which hasn't been a problem (although I now have a small amount of water in the oil presumably from seeping past the rings/valves after hydrolock condition, after I just changed the oil -again- last week). If it was getting into the oil from the intake/gasket the oil level would continue to rise and get worse as it circulates water, this doesn't appear to happen. Oil on the dipstick is clean and at an appropriate level.

 

[jdubslopro]

Re: Merc keeps hydrolocking

Update:
Ran the engine, drained the manifolds Wednesday, left the drain plugs out. Went to turn it over today (saturday) and it was hydrolocked again. So I think it's safe to assume that the manifolds/risers are not the cause of this issue. I made this attempt RIGHT before I was about to head out to pick up a brand new set of manifolds/risers, and have since decided to try to locate the source of water intrusion. Is there any "test" I can do to try and pinpoint the issue? I don't know anyone that can do a leakdown test, and I'm not sure that a pressure test on the coolant system is really going to be too helpful considering it's an open cooling system.

 

[Don S]

Re: Merc keeps hydrolocking

Not buying it yet not being the exhaust yet, disconnect the water hoses going to the exhaust manifolds and elbows and aim them to the bilge. Then start it up again with muffs. but only run it for about 10 or 15 seconds to make sure there is water to everything else.
Shut it off and let it set for a while and see if it's still hydrolocked.

What is the Merc SN of your engine?

 

[tpenfield]

Re: Merc keeps hydrolocking

The only other "test" that I can think of would be a cooling system pressure check . . . It is a bit tricky with an open cooling system, but you should be able to hear if/where there is a leak.

 

[NHGuy]

Re: Merc keeps hydrolocking

What cam is in the rebuilt motor? Not some hot lumpy car cam right? Cause if it's a sexy sounding car cam you might be getting reversion water in the combustion chambers.
It's still worth another shot at the manifold water leak test too, just to be certain.
I have a way you can isolate and pressure test the engine cooling system but for the life of me I can't think of a reason to do it.
Hydrolock after a shutdown is usually exhaust.

 

[jdubslopro]

Re: Merc keeps hydrolocking

Sorry for the delay in response. I ended up getting brand new manis and risers. Lo and behold, it is hydrolocked...again. And there's some definite water mixing in the oil under the intake manifold. The water in the cylinders is clean, no oil, no foam. I cannot for the life of me figure out where the water is coming in. I have the motor out again, pulled one of the heads due to a warped intake valve that I'm replacing, and still trying to figure out this damn water intrusion. I thought I was possibly rain water coming into the intake, but it's been a LOT of water. And from the time I last drained the cylinders it has not rained, and I have not run the engine. I removed exhaust manifolds, cleared out all the water last Wednesday, left the plugs out, sprayed some fogging oil in each cylinder and didn't crank it afterwards. Today it had water in there again. I am REALLY regretting not having bought a crate engine at this point. Couldn't beat the price I got this setup for...until things like this happen. Luckily I have the tools...

Don, it's 0M011557

 

[jdubslopro]

Re: Merc keeps hydrolocking

Also wanted to add, it is the factory merc cam that came with the motor, and it runs perfect after removing the water, although I had low compression in one cylinder from a bad valve. 180psi in 1345678 90psi in 2. Motor maxed out at 50mph@5,000 rpms with a 1.62 ratio alpha 1 with 19p 4-blade. prop. As you might guess, this is grossly underperforming, my v6 had this same performance. My guess is this setup should be turning over 6000 rpms (obviously I won't allow it, just hypothetically) and my plan is to reprop to a 23p 4 blade.

But I wanted to make the point that whatever water gets in the cylinders takes a while of just sitting without being run. I don't know for sure exactly how long. But 2-3 days seems to be long enough.

 

[jdubslopro]

Re: Merc keeps hydrolocking

I dropped the starboard (even side) head off at the machine shop today. I'm going to have them pressure test it and reseat the new valves (doing the intake and exhaust on #2). They weren't equipped to pressure test the intake manifold, so I will have to devise a way to do that myself.
I just can't see anything having developed a crack or break. I rebuilt this motor in September, installed it in the boat, ran it to seat the rings, shut it off and winterized it. I ran it 4-5 times in the spring trying to get things running properly over the course of a few weeks, and never had a hydrolock issue once. I then brought it to a marine mechanic to troubleshoot the electronic issues I was having, and they day I trailered it home and put it in the water it started having hydrolock issues.

 

[chimmike]

Re: Merc keeps hydrolocking

depending on the cooling jackets, it could be possible to have a leaky headgasket without oil/water mixing. I just had this issue on my car....lifting the cylinder head from too much boost. Coolant was burning away like crazy but no mixing with oil.

 

[jdubslopro]

Re: Merc keeps hydrolocking

Got the word back from the machine shop. Pressure test results came back showing a good head no cracks and even mating surface. Figured this would be the case. Guess its up to me to test the intake. I'm ruling out bad cylinders at the moment...can't imagine there would be multiple failures at once.

 

[Glastron3.0GLP-C]

Re: Merc keeps hydrolocking

ALL the cylinders get water in them.

Bad cylinder head gasket or cracked cylinder head or cylinder are automatically out of the question if ALL cylinders get water. Chances all cylinder are leaking is 1 in a million. You shouldn't touch the head based on this symptom.

starts and runs fine, doesn't get any more water in there

Very clear that water is not coming from cylinder in operation.
So have you checked these possible causes from Bulletin No. 2001-13:
1.Ignition misfire (fouled spark plug).
2.Engine run-on (dieseling).
3.Extended idling before shutting the engine off.
4.Doing ‘throttle chops’
5.Missing internal shutters in exhaust tips

 

[jdubslopro]

Re: Merc keeps hydrolocking

Yes I have checked all those I have had that bulletin open on my phone for a week. It's not from a poor running condition, something about when it sits.

 

[Glastron3.0GLP-C]

Re: Merc keeps hydrolocking

Is the temperature of the manifold above 120? Check with a infrared gun or your hand. If running cold condensation collects in them and run back from the exhaust valves to the cylinder.
Another test:I would lose the manifold 1/4 inch from the head and see if any water is dripping afterwards. This will end the manifold leak discussion.

 

[jdubslopro]

Re: Merc keeps hydrolocking

Temp on the gauge sits right around 160 once it warms up. Exhaust manis are warm but not burning hot. I'm waiting on another head gasket, head bolts, and intake mani gaskets to put this together for the...I think 3rd time.
There is enough water to fill a cylinder and put some water in others, so I doubt it's condensation.