Engine Hydro-locked! What???

[Jimmy Buoy]

Sharing info on CSR has helped me plenty - time for me to share my experience in hopes that it will help others.

Left the marina the other day. Both Merc 4.3 MPI Bravo III's purring well. Ten minutes later running at 3200RPM I hear a SOLID ALARM and the port engine lowers its RPM without me touching the throttles. I get the boat off plane, go into neutral and stop the engines. What the heck!?!

Inspection of the engine room reveals that the serpentine belt on the port engine came off and was laying on the ER floor. That means no Raw Water pump for about 30 seconds @3200RPM. I place my hand quickly on the top of the exhaust risers - too hot to keep my hand on! Damn. The side of the exhaust manifolds are even hotter so no touch! Grab my tool box and quickly reinstall the belt but decide NOT to start up the boat right away since it would introduce cool lake water into the really hot cast iron exhaust manifolds and didn't want to risk cracking the casts. Anchored and enjoyed the beautiful day for a bit!

Two hours later, I went to start the engine. The crank only turned an inch or so and abruptly stopped. Battery voltage was 14vts so it made me suspicious that something was stopping it from rotating. I decided to start pulling plugs starting with #2. It looked suspiciously wet. #4 was dry and #6 when removed released a stream of uncomfortably hot water (about 1/2 a cup). Never had that happen. Removed #1, 3 and 5 on the other head and they were all dry. Spun the starter and water sprayed out of the #2 and #6 plug holes but seemed to be lessening.

Tucked my tail between my legs and putted back to the dock on the stb engine. Sprayed WD40 into all the cylinders there and spun it again just to try and protect the internals from rust.

I'm thinking Head Gasket or Cracked Head (from overheating) and am ready to pull the boat and start working to remove the "wet head" but decide to go and buy a compression tester first just to see what I'm working with here.

Any ideas???

 

[Espos4]

What about this:

Fog it, put the plugs back in and see if it runs.

Pull the plugs again and check for water.

 

[Jimmy Buoy]

What about this:

Fog it, put the plugs back in and see if it runs.

Pull the plugs again and check for water.

Good idea, but just concerned that I might hydrolock the engine again if there is more water intrusion and if that happens after it starts, the torque could damage connecting rods or bearings. A compression test first won't hurt. If compression looks good the plugs will go back in and see how she goes!

 

[Scott215]

I agree,spin without plugs. Fog it
Re install plugs and see if the engine will start. Then check heads. Probably head gasket. Just see if it still runs

 

[Little Ducky]

Source out a rebuilt or new engine to get a cost and then while you are tearing into yours to diagnose the damage you will have a educated value of how much you want to spend on the old lump compared to just remove and replace.

If anyone was paying for labor to rip down an old lump to rebuild it the money can go quite quickly...... if you are able to DIY you have to think how much is your time worth?

 

[Strecker25]

Maybe the hydrolock was from water rushing up the exhaust? How quickly did it come off plane?

 

[Yendor]

Maybe the hydrolock was from water rushing up the exhaust? How quickly did it come off plane?

While this could/would be the best case scenario, wouldn't it be odd for 2 cylinders on the same side to exhibit symptoms while none on the other bank did? I would think the stated results would rule out that likelihood, with the odds favoring a head gasket as Scott opined.

 

[Jimmy Buoy]

OK - got a compression tester and happy to report that all cylinders are close to the same PSI. Only problem is that the new gauge (cheaper Chinese from a discount supply co) must be poorly calibrated. PSI as follows...
Cylinders #1,2,3,4,5,6 are 220, 230, 225, 229, 212, 230 lbs. Not likely to be that high compression, but with them all near the same reading I ruled out a bad head gasket & decided to put the plugs back in and fire her up (checked condition of engine oil first - perfect).

She stumbled a bit for 5 seconds (probably burning off remaining moisture and WD40) then ran like a champ!

Both my engines are relatively new remanufactured long blocks (only 80hrs) replaced by the previous owner. The other parts would have come off the original engines which had 300 hours.

Think I determined why the belt skipped off in the first place. The alternator pulley was loose and wobbling since the nut had become loose enough to be turned by hand (with the belt off). It's back on and torqued with an electric impact wrench.

But what happened here?? I came off plane quickly, but kept both engines running (with the alarm sounding) until getting into neutral then shut off the port engine first (alarm of course stopped) then the stb was shut down. Checking VVM, the fault recorded was NOT overheat, but LOW WATER PRESSURE. Makes sense with the belt driven raw water pump disabled. I had taken temp readings at the time with an infrared gun at the heads and various points on the exhaust manifolds with non being over 195 degrees with the engine off.

 

[PlayDate]

Sharing info on CSR has helped me plenty - time for me to share my experience in hopes that it will help others.

Left the marina the other day. Both Merc 4.3 MPI Bravo III's purring well. Ten minutes later running at 3200RPM I hear a SOLID ALARM and the port engine lowers its RPM without me touching the throttles. I get the boat off plane, go into neutral and stop the engines. What the heck!?!

Inspection of the engine room reveals that the serpentine belt on the port engine came off and was laying on the ER floor. That means no Raw Water pump for about 30 seconds @3200RPM. I place my hand quickly on the top of the exhaust risers - too hot to keep my hand on! Damn. The side of the exhaust manifolds are even hotter so no touch! Grab my tool box and quickly reinstall the belt but decide NOT to start up the boat right away since it would introduce cool lake water into the really hot cast iron exhaust manifolds and didn't want to risk cracking the casts. Anchored and enjoyed the beautiful day for a bit!

Two hours later, I went to start the engine. The crank only turned an inch or so and abruptly stopped. Battery voltage was 14vts so it made me suspicious that something was stopping it from rotating. I decided to start pulling plugs starting with #2. It looked suspiciously wet. #4 was dry and #6 when removed released a stream of uncomfortably hot water (about 1/2 a cup). Never had that happen. Removed #1, 3 and 5 on the other head and they were all dry. Spun the starter and water sprayed out of the #2 and #6 plug holes but seemed to be lessening.

Tucked my tail between my legs and putted back to the dock on the stb engine. Sprayed WD40 into all the cylinders there and spun it again just to try and protect the internals from rust.

I'm thinking Head Gasket or Cracked Head (from overheating) and am ready to pull the boat and start working to remove the "wet head" but decide to go and buy a compression tester first just to see what I'm working with here.

Any ideas???

I thought your boat has closed cooling......(antifreeze in the block) if that is the case it isn't a head gasket or a cracked head. You would know that pretty quickly by the depletion of the coolant. Even raw water will turn the engine oil into chocolate milk pretty quickly with a head gasket, cracked block or head.

Also.....I'm a little fuzzy on exactly what was the sequence of events. So both engines are cruising.....one goes into alarm and drops to idle. Was the alarm for oil pressure or temperature? The fact that it was still running without the belt is also interesting. It won't run hydrolocked but it would overheat.....so where did the water come from?

The only practical explanation is a one time event when you stopped and water pushed against the exhaust system after you shut the engine down creating a reversion event. In that case ......hopefully no harm except for the water scare.

The bigger mystery to the sequence is the belt coming off in the first place. That troubles me. Serpentine belts usually don't come off unless the tensioner fails or one of the rotating assemblies seizes up and throws the belt.

As others have mentioned.....taking the abundance of caution approach....I would do:

1) Compression Check
2) Remove the belt and turn each of the accessories by hand.
3) If all checks out ....re tension the belt and fire it up.

I suspect....something is amiss with a belt driven accessory so keep an eye on it because if that is the case....it will happen again.


edit:

Looks like you solved it.....

 

[Jimmy Buoy]

I thought your boat has closed cooling......(antifreeze in the block) if that is the case it isn't a head gasket or a cracked head. You would know that pretty quickly by the depletion of the coolant. Even raw water will turn the engine oil into chocolate milk pretty quickly with a head gasket, cracked block or head.

Also.....I'm a little fuzzy on exactly what was the sequence of events. So both engines are cruising.....one goes into alarm and drops to idle. Was the alarm for oil pressure or temperature? The fact that it was still running without the belt is also interesting. It won't run hydrolocked but it would overheat.....so where did the water come from?

The only practical explanation is a one time event when you stopped and water pushed against the exhaust system after you shut the engine down creating a reversion event. In that case ......hopefully no harm except for the water scare.

The bigger mystery to the sequence is the belt coming off in the first place. That troubles me. Serpentine belts usually don't come off unless the tensioner fails or one of the rotating assemblies seizes up and throws the belt.

As others have mentioned.....taking the abundance of caution approach....I would do:

1) Compression Check
2) Remove the belt and turn each of the accessories by hand.
3) If all checks out ....re tension the belt and fire it up.

I suspect....something is amiss with a belt driven accessory so keep an eye on it because if that is the case....it will happen again.


edit:

Looks like you solved it.....

Thanks John. Sorry - should have clarified Raw Water Cooling (No Antifreeze).

Sequence of events were as follows... Started the engines cold, ran them for a few minutes at the dock, then idled while leaving the marina. Once in open water got up and on plane then backed off the throttles to the normal cruise RPM of 3200 and synced engines. After about 10 minutes a solid alarm sounded, I felt the boat immediately slow, and the engines sounded immediately out of sync, as I throttled down to come off plane I scanned the gauges and noticed that the port engine's RPM's had dropped below 1500 even before pulling the throttles back that far. Once off plane and the following sea had passed I pulled the controls to neutral and shut down the port engine. This all happened within about 30 seconds. The alarm stopped once I turned off the port engine which verified it as being the alarm source. I then shut down the stb and started to investigate in the ER.

I later thought to check my Vessel View Mobile app to see if it recorded the fault - it did. "CRITICAL - WATER PRESSURE, Stop engine and check for plugged water inlet. If condition persists return to port"

You're right about the accessory pulley being the problem. As mentioned - the alternator pulley was able to be moved inward or outward on its shaft about 1/4" with the nut backing off. Torqued back on now!

Still not sold on water pushing against the transom flooding the engine since both engines were still running and in gear at idle when the following sea caught up to the boat.

 

[Jimmy Buoy]

Ok - I think this explains what happened with my engine. Interesting!

 

[PlayDate]

Ok - I think this explains what happened with my engine. Interesting!

How is your exhaust routed on the Formula?

 

[Scott215]

That is a great example of what can happen. Love it

 

[Yendor]

That's great news, Very happy for you.
Lends credence and more proof for the old axiom "Keep the Faith".

This is good news for anybody that's paying attention,
in that, the bar has been raised for 'best case scenario'.

 

[Jimmy Buoy]

How is your exhaust routed on the Formula?

Exhaust exits the risers, down into the Y-Pipe, past the flappers and out via the transom assembly but also through the prop hub when higher RPMs. No thru-hulls on this boat - nice and quiet! Plus it's V6's so no V8 rumble anyway.

 

[Jimmy Buoy]

That's great news, Very happy for you.
Lends credence and more proof for the old axiom "Keep the Faith".

This is good news for anybody that's paying attention,
in that, the bar has been raised for 'best case scenario'.

Thanks! Just trying to spread the word in case something similar happens to another member! I came close to tearing down the engine in my driveway. That would have been a huge error!!

 

[Scott215]

It makes a lot of sense. Hopefully never have to go through that

 

[aerobat77]

Thanks! Just trying to spread the word in case something similar happens to another member! I came close to tearing down the engine in my driveway. That would have been a huge error!!

I would monitor the situation optimistic but not yet open the champagne . Its still odd to me you hydrolocked just 2 cylinders on one bank with this explanation.

Not calling for bad luck but you might have a very minor crack that opens only at high load / longer run on plane and does not show up at compression testing and a short test run.

Just monitor if anything really stays fine .

 

[Scott215]

Just keep a really good eye on temp

 

[Jimmy Buoy]

I would monitor the situation optimistic but not yet open the champagne . Its still odd to me you hydrolocked just 2 cylinders on one bank with this explanation.

Not calling for bad luck but you might have a very minor crack that opens only at high load / longer run on plane and does not show up at compression testing and a short test run.

Just monitor if anything really stays fine .

Thanks for the comment, and yes time will tell if all is good. I'll take the win for now but definately will watch the engine's vitals for the near future. VVM is great for this!

I only believe on cylinder #6 had enough water to hydrolock the engine. The other one was #2 that seemed to have some moisture on the plug but no appreciable amount of water (just some vapour part of which was gasoline) shot out as the engine was spun to clear any standing water.

Hope to take her out for a run tomorrow to either rebuild trust or reveal a bigger issue (hopefully the former).