Strange Scenario - Water in cylinders - hydrolocked

[arob]

Hey all, i am in need of some advice...

i bought a 98 formula 34pc with mercruiser 7.4 LX and B3's in the fall, had it winterized before it was transported to my marina, and it sat there all winter. I put the boat in the water yesterday for the first time and had some issues. The boat fired up and ran great, at first. Shortly after leaving the dock, the starboard engine started to heat up. I shut it down at 190 degrees, and idled on the other engine over to my slip at the marina. I went out and bought another water pump impeller and replaced it the same day (the old one was toast)...no big deal. it was about 2 hours from the time it ran to the slip, and the time i got the water pump replaced and tried to restart.

now the odd part...when i went to start the motor again, it turned 1/4 turn and locked up. i pulled all 8 sparkplugs and it turned over fine, but it shot water out of most of the cylinders. it came from both sides of the motor. it was a significant amount of water, and obviously enough to hydrolock the motor. all 8 cylinders are moving, as i tested by putting my finger over the spark plug hole, that doesn't verify that it doesn't have a bent rod, but at least it didn't break one. this is a problem to investigate later, but i need to find where the water came from. sidenote, is the starter motor on a 7.4 strong enough to bend a rod?

I'm thinking that it has to come from either intake manifold or exhaust manifold. There is no water in the oil, so the only way water can get to the cylinders without getting in the oil is either the intake or exhaust manifolds. i took the port manifold and riser off and inspected. i can't seem to find anything obvious where it may be cracked. i filled the manifold full of water and let it sit on the dock for a few hours and it did not leak down. next, i wanted to test the riser, but i don't know how i can seal the riser to be able to see if it leaks at all. any ideas how to seal the angled end where the boot goes to the y-pipe? Also, what is the small hole (maybe 1/4") at the top of the riser (on the inside)? it is almost in the center of the riser exhaust port.

so my preliminary theory goes like this...There was pink antifreeze still in the outlet line from the old raw water pump when i pulled it to replace the impeller. obviously it hadn't moved much water through the engine. i'm thinking the water pump was inadequate in the fall for when the marina winterized the engine, and didn't pump antifreeze all the way through the motor as it should. also another interesting observation is that when i pulled the thermostat housing, there was water below the thermostat. The motor had been run for a few minutes, but since there was still antifreeze in the outlet from the raw water pump, it hadn't moved any through the motor while running. if there was water below the thermostat, that means it was in there all winter...right? Also the fact that there was even a thermostat in the motor after being winterized is a mystery to me too. i always pulled my thermostats when i winterize to make sure antifreeze goes all the way through the motors.


anybody have any other ideas where the water could come from or any other things i can do to test? maybe some of you can verify or refute my theories as well? the boat was surveyed and sea trialed in the fall before buying it, and everything was fine with both engines. the only thing that happened after survey and sea trial was they were winterized by the marina where i bought it.

 

[Justin Kennedy]

Head gasket?

 

[NHGuy]

First off. Welcome to the forum!
My 88 5.7 did that when the exhaust manifold cracked leaked cooling water into the exhaust. But I only had it on one side.
The reason they run wrong and heat up is because the water displaces air that would be in the combustion chamber thereby raising the compression and causing detonation.

I'd also check compression just in case. But there's a good chance it's from the exhaust.

 

[arob]

Head gasket?

i thought the same thing at first, but both sides? i find it hard to believe both are bad at the same time. Water was in both left and right banks of the motor.

 

[arob]

First off. Welcome to the forum!
My 88 5.7 did that when the exhaust manifold cracked leaked cooling water into the exhaust. But I only had it on one side.
The reason they run wrong and heat up is because the water displaces air that would be in the combustion chamber thereby raising the compression and causing detonation.

the impeller was completely gone, so i know that played a major role in the heating up. i can see what you're saying when running with some water though. the whole "water in both sides" is what has me wondering. and the fact that there was antifreeze still in the impeller outlet after running a few minutes tells me that no water moved in that engine for the short time it ran. also there was all water in the manifolds, risers, and below the thermostat, telling me that there was no antifreeze in them all winter.

is there any other explanation here that i'm missing or maybe a part of the cooling system i misunderstand?

 

[NHGuy]

In a bigger boat like yours the engines are set low as compared to the water line. Do your risers go above the level of water outside the boat? If not the water can fill up your engines.
Did the boat get surveyed before you bought it?
It's also possible that when you tried to restart the engine some of the water might have gotten shoved out into the intake manifold and made it's way to the other side.

 

[NHGuy]

Since there is a chance that water stayed in there all winter you ought to check for a cracked block too. :grumpy::grumpy:

 

[arob]

yea im probably going to have to pull the intake at least to check for any cracks, but thats still no guarantee that there isn't a crack somewhere else. the engines and exhausts are stock, so i would hope they would be designed to be above the water line. the risers come almost to the top of the engine compartment, so i would estimate the top of the riser is at least a foot above the water line. there is no thru hull exhaust, so i wouldn't think flappers would be an issue.

the boat was surveyed prior to buying it and it ran fine. we started and stopped the engine many times and never had any issues. it even started on saturday easily after sitting all winter and ran fine until it started to heat up. the heating up was definitely caused by the bad water pump impeller. the only people who touched it since it was surveyed was the marina who wintereized it.

do you think i have a case with the surveyor or the marina? i know the surveyor was a 2nd generation, certified, and insured guy, but honestly i don't think he missed anything. considering the boat ran fine on sea trial and didn't overheat, what more can he do? i think my gripe is with the marina who winterized it (if you ask me). what do you think?

 

[Maclin]

The starter does not have the torque to bend a rod, standard ones anyways. When a rod gets bent or breaks from a hydrolock what happens is one cylinder fires off with the starter and that is when the next cylinder on a compression stroke gets the rod bent. In my opinion, since all cylinders had water in them none could have fire off and the next full compression stroke stopped it. Probably.

 

[jimmbo]

Since the motor had been running the comment of water being in the cylinders all winter makes no sense, Water could have backed up in the exhaust manifolds from backwash when you were returning back to dock using one engine. One cylinder had its exhaust valve open, filled with water and hydro-locked. When you removed the plugs it allowed the engine to spin and drained the remaining water in exhaust manifold into the cylinders as the exhaust valves opened, then expelled the water through the spark plug holes

 

[Bondo]

maybe some of you can verify or refute my theories as well?

Ayuh,...... Welcome Aboard,.... Perplexing problem,..... To test the cracked intake theory,....

Drain, 'n Isolate the block's coolin' passages from everything else, 'n pressurize to 'bout 15psi,....
If the intake is cracked into the plenum, you'll hear air escapin' through the carb,....

Intakes Usually crack into the oil galley,.... on the bottom, rather than inside,......

If ya pull the exhaust manifolds, 'n remove the risers, if ya see any Rust, there was water there,...
Follow the rust tracks,....

All black, 'n no rust, no water there,....

 

[arob]

The starter does not have the torque to bend a rod, standard ones anyways. When a rod gets bent or breaks from a hydrolock what happens is one cylinder fires off with the starter and that is when the next cylinder on a compression stroke gets the rod bent. In my opinion, since all cylinders had water in them none could have fire off and the next full compression stroke stopped it. Probably.

Ok good. I didn't think the starter had the umph to bend one, but wasn't real sure. It definitely didn't fire off a cylinder, it just stopped.

Since the motor had been running the comment of water being in the cylinders all winter makes no sense, Water could have backed up in the exhaust manifolds from backwash when you were returning back to dock using one engine. One cylinder had its exhaust valve open, filled with water and hydro-locked. When you removed the plugs it allowed the engine to spin and drained the remaining water in exhaust manifold into the cylinders as the exhaust valves opened, then expelled the water through the spark plug holes

[/QUOTE]

My comment must have been unclear. I think there was water in the cooling side of the motor all winter, not the cylinders. It fired and ran post-winter, so you are right, there couldn't have been water in the cylinders all winter. I was saying that antifreeze came out of the outlet of the raw water pump, so i know it didn't pump any water into the cooling system...and upon pulling the thermostat housing, there was water in the cooling passages below the thermostat. This is what makes me think there was water in the engine and thus either cracking an intake and/or exhaust manifold.

You have a good point of backwash, but how would that happen? The boat does not have thru hull exhaust. Also, i shut the engine down and idled back to the dock on one engine. I fired the second engine for 30 seconds to a minute when i was right at my slip so i could back into the spot on both engines (its pretty tight at my marina, and the starboard engine is my power steering engine). So it was running up until i pulled the into my slip. is backwash still an issue with through prop/bell housing exhaust? is there still flappers in the y-pipe or elsewhere that may be bad?

You also have a good point of turning over with no plugs and allowing the water into the cylinders that may have been sitting in the manifold. So are you agreeing with me that its most likely a cracked exhaust manifold and/or riser? I did plug off the bottom hose fitting of the port side manifold and filled it with water. it sat for a few hours and never drained down. i haven't however checked the risers. i need to figure out a way to plug them up and fill them with water as well. Any ideas how to plug them up to test?

Ayuh,...... Welcome Aboard,.... Perplexing problem,..... To test the cracked intake theory,....

Drain, 'n Isolate the block's coolin' passages from everything else, 'n pressurize to 'bout 15psi,....
If the intake is cracked into the plenum, you'll hear air escapin' through the carb,....

Intakes Usually crack into the oil galley,.... on the bottom, rather than inside,......

If ya pull the exhaust manifolds, 'n remove the risers, if ya see any Rust, there was water there,...
Follow the rust tracks,....

All black, 'n no rust, no water there,....

good suggestion with following the rust. the port side manifold is all black, the starboard manifold has some rust flakes floating in the water laying in the bottom. if the intake usually cracks into the oil galley, then i would assume i'd probably see water in the oil, which i don't as of yet. it hasn't been run very much, so it could still take on water eventually, but hasn't yet. this is a 454 lx mpi, so are they the same as the carb'ed ones? If i isolate the two hoses that go to the bottom of each of the exhaust manifolds, and plug off the hose at the raw water pump, that should isolate the cooling system, correct? then i can just find a spot to thread in a fitting and put regulated air to it. anything i'm missing?

 

[Twin Spirit]

I just had the same thing happen to one of my MX 6.2 MPI engine. Started up and ran fine for 10 min. Then started running rougher and I noticed the temp started shooting up so I shut it down. When it cooled down I tried restarting it but it locked up. I drained the block and it was still full of pink anti-freeze so I replaced the thermostat. I removed the plugs and all 8 cylinders had water in them. I checked the fuel filter and there was no water in it so my next guess is the fuel cooler letting water into the fuel line . It's the only common component that could add water to all 8 cylinders. I can't think of any other component that would put dirty water into all the cylinders when the block was still full of wintrizing antifreeze.