Mercruiser 4.3 LX Gen+, Hydrolock, no water in oil.

[needarp]

Hello all,

I have a boat with a 4.3 Mercruiser LX Gen+ with Edelbrock Performer 2114 intake manifold, Edelbrock 1409 4 barrel carburetor, and a Delco EST ignition system. Also have GLM 2 piece exhaust riser/manifolds. All engine upgrades installed less than 50 hours ago. Stock Mercruiser intake manifold was replaced just before the upgrades due to cracking from last owner's lack of winterization.
The boat began acting up last summer. Boat would run great for a few minutes then bog down and shut off. Motor would restart immediately, run again for a few minutes, and then bog down and shut off again. I changed plugs, wires, distributor cap, and I thought this eliminated the issue. Only used the boat briefly though after so now I'm not sure.
This spring the same issue showed up again the first time I took the boat out. I thought I had an ignition pickup coil issue so I pulled the distributor, replaced the coil, and re-timed the engine. Took the boat out yesterday and the engine ran like new for about 10 minutes and then bogged and shut off again.
This time the engine hydro locked. I pulled the spark plugs and cranked the engine, got a bit of water out of cylinder 1, a stream out of cylinder 2, and a bit out of cylinder 4. Zero water in the oil.
Since I had water in cylinders on both sides of the block I thought it unlikely to have a double head gasket failure. I compression tested the engine cold this morning (afraid to start it up) and compression was 170+ on all 6 cylinders.
I pulled the intake manifold thinking it must be the culprit but the Edelbrock 2114 only uses the front water passage and it appears to be completely separated from the intake ports so I don't see how a cracked intake manifold could be the culprit.
The exhaust manifolds/risers were obviously drained with winterization and probably have under 30 hours on them since new. Does it seem reasonable to have a failure on both sides at the same time?
I'm at a loss and would appreciate any ideas you all might have.

PS- I've included a photo of the Edelbrock 2114 intake manifold. You can see that cylinders 1, 2, and 4 are near the water passage. Is there any chance that failed intake manifold gaskets could cause this issue?

 

[Lou C]

If the gasket for the intake failed at the water passages it is more likely to put water right into the cam valley and into the oil. Water in the cyls might more likely have come from the exhaust system, do you have wet joint exhausts or dry joint? If wet joint it isn't that uncommon for those gaskets to leak. If you can remove the manifold and elbow as a unit (after draining the water out) and look in the exhaust ports that match up with the cyl head ports, see if you see evidence of rust trails there. Might just need new gaskets/checking flatness of sealing surfaces.

 

[itsathepete]

Hydrolock may be due to engine shutting off unexpectedly. Was it at significantly higher rpm than idle when it happened?

 

[needarp]

Hydrolock may be due to engine shutting off unexpectedly. Was it at significantly higher rpm than idle when it happened?

Hydrolock may be due to engine shutting off unexpectedly. Was it at significantly higher rpm than idle when it happened?

We were cruising at over 70% throttle when it bogged and shut off.

 

[needarp]

If the gasket for the intake failed at the water passages it is more likely to put water right into the cam valley and into the oil. Water in the cyls might more likely have come from the exhaust system, do you have wet joint exhausts or dry joint? If wet joint it isn't that uncommon for those gaskets to leak. If you can remove the manifold and elbow as a unit (after draining the water out) and look in the exhaust ports that match up with the cyl head ports, see if you see evidence of rust trails there. Might just need new gaskets/checking flatness of sealing surfaces.

I have the GLM 58222 setup, so wet joint. That's a great idea, thanks!

 

[Lou C]

Sometimes what can happen is if the engine dies at higher than idle speed it can actually suck water back into the engine due to the vacuum developed in the exhaust system. Given what you just said, it is more likely that, (engine dying at above idle speed) than leaky exhaust. If it were leaky exhaust it would more likely hydrolock after sitting a while, not when running. When running the pressure of the exhaust will push water out that may be leaking in. Do you see any rust trails from the joint between the manifold and elbows?

 

[Rick Stephens]

Zero water in the oil.

Note that if you get water in the cylinders it is damn unlikely that none gets into the oil. If you are judging if water is not present by virtue of the dipstick, it won't show on a dipstick until enough oil is emulsified with the water to turn it to cream.

I have the same motor setup as you do. If I had water in cylinders while running I would suspect intake as well. Only other alternative is a cracked head on that side. Exhaust water ingress only occur when you stop the boat, they will not fill cylinders while running along..

 

[Lou C]

Remove the oil fill cap and look inside.
what a blown head gasket does....
first sign of this though was difficulty starting and rough running
found water in cyl #2 and just a bit in #1
upon dis-assembly found both head gaskets blown right near a water passage near each cylinder
water in the oil takes a while to show up on the dipstick

 

[Rick Stephens]

Remove the oil fill cap and look inside.
what a blown head gasket does....
first sign of this though was difficulty starting and rough running
found water in cyl #2 and just a bit in #1
upon dis-assembly found both head gaskets blown right near a water passage near each cylinder
water in the oil takes a while to show up on the dipstick

View attachment 365901

Just thinking here, have you ever heard of a blown head gasket hydro-locking a running motor? Seems unlikely. And the first symptom of that major of a gasket leak would be overheating.... This should be easy to find with a pressure test of the cooling system.

 

[Lou C]

Just thinking here, have you ever heard of a blown head gasket hydro-locking a running motor? Seems unlikely. And the first symptom of that major of a gasket leak would be overheating.... This should be easy to find with a pressure test of the cooling system.

agreed that would be very rare, on mine it didn't hydrolock it, just a small amount of water would seep in when it sat for a day or so.
I was able to see the exhaust gas getting into the water exiting the stat housing via the hoses that feed the manifolds.
If I checked for water right after shutting it off there was none. Let it sit a day and just a bit would get pumped out of #2 and a mist out of #1.
I think the OP's motor hydrolocked from stalling at high rpm, given what was reported.
Under certain conditions you can get vacuum in the exhaust and V/P actually fitted vaccum break valves to the exhaust elbows to reduce the chance of reversion on the Vortec 4.3s. They were not necessary on the pre-Vortecs but the cam specs changed enough that they thought that was needed. Don't think Merc agreed though....

 

[needarp]

So I pulled the exhaust manifold and riser on 2-4-6 side of the motor where i had water in 2 cylinders. No evidence of gasket failure, although I am attaching photos for more expert eyes. What I did find, however, floored me. See anything missing in the last photo?

 

[Lou C]

Well yeah no flappers!!! that could explain it! wonder if this boat had a past overheat that melted em, or if they just fell off.
In the second pic of the manifold its hard to tell but I think I see a bit of rust in the center exhaust gas section but that could be from water rushing up the Y pipe and elbow when the engine stalled.

 

[needarp]

Note that if you get water in the cylinders it is damn unlikely that none gets into the oil. If you are judging if water is not present by virtue of the dipstick, it won't show on a dipstick until enough oil is emulsified with the water to turn it to cream.

I have the same motor setup as you do. If I had water in cylinders while running I would suspect intake as well. Only other alternative is a cracked head on that side. Exhaust water ingress only occur when you stop the boat, they will not fill cylinders while running along..

But if water pushed up the exhaust after the engine died at 35 mph due to the absence of exhaust flappers I may have no water in oil, correct? Changing oil either way, just wrapping my brain around this all.

 

[Lou C]

It does get into the oil via the cyls. Mine had mayo under the valve covers & in the cam valley. This was from just a little water in #2 and #1. The longer it sits there the worse it is. So get it up & running ASAP

 

[Rick Stephens]

Water will pass by the rings into the oil

 

[needarp]

It does get into the oil via the cyls. Mine had mayo under the valve covers & in the cam valley. This was from just a little water in #2 and #1. The longer it sits there the worse it is. So get it up & running ASAP

Oil is out. Re-gasketing and new flappers as soon as I can get them. Hopefully back on the water by the weekend to figure out the ignition issue.

 

[MarcelSydney]

Not sure what years yours is, but I have a 4.3L that was doing similar (turning off randomly, usually under heavy load). It has an electric fuel pump.
Turns out it was the oil pressure switch (which i worked out from a number of different users on this forum). Check the terminals aren't corroded, or the switch isn't busted. You can jump the wires together after you're boats running to test it. If it doesnt shut off, might be it. Apparently the oil pressure switch runs the fuel pump while the engine is running and cuts the fuel pump off if oil pressure drops. It's on the port side of my engine near the oil filter.

This could explain your engine shutting off. The rest of their posts (like the flappers) could be why water got in there, that's above my pay grade!

 

[needarp]

Not sure what years yours is, but I have a 4.3L that was doing similar (turning off randomly, usually under heavy load). It has an electric fuel pump.
Turns out it was the oil pressure switch (which i worked out from a number of different users on this forum). Check the terminals aren't corroded, or the switch isn't busted. You can jump the wires together after you're boats running to test it. If it doesnt shut off, might be it. Apparently the oil pressure switch runs the fuel pump while the engine is running and cuts the fuel pump off if oil pressure drops. It's on the port side of my engine near the oil filter.

This could explain your engine shutting off. The rest of their posts (like the flappers) could be why water got in there, that's above my pay grade!

Good call! I'll give this a try once the boat is back together.

 

[needarp]

Not sure what years yours is, but I have a 4.3L that was doing similar (turning off randomly, usually under heavy load). It has an electric fuel pump.
Turns out it was the oil pressure switch (which i worked out from a number of different users on this forum). Check the terminals aren't corroded, or the switch isn't busted. You can jump the wires together after you're boats running to test it. If it doesnt shut off, might be it. Apparently the oil pressure switch runs the fuel pump while the engine is running and cuts the fuel pump off if oil pressure drops. It's on the port side of my engine near the oil filter.

This could explain your engine shutting off. The rest of their posts (like the flappers) could be why water got in there, that's above my pay grade!

You nailed it! Bypassed the oil pressure switch and the boat runs perfectly! Thanks for the help.

 

[MarcelSydney]

You nailed it! Bypassed the oil pressure switch and the boat runs perfectly! Thanks for the help.

Ripper! Great to hear.