Broken Valve ?? Questions ?? Valve Head Broken Where It Connects To Stem

[jan9898]

New 454 Big Block with just about 45 hours on it, thru hull exhaust. This new engine was installed after freeze damage from the original motor.

Was running at about 50mph last year with the new engine when the alarm went off and simultaneously the engine shut down completely, this happened about 1 mile after a 30 minute no wake zone. I tell this becasue the boat was running in the water without stopping for atleast and hour before it shut-off

I Got towed in etc. Checked the dipstick, the oil level was very high and smelled of gas.

Returned the boat and engine back to the marine shop. They pulled the engine, the first mechanic said I must have sucked something in, fried the impeller and the engine overheated. Second mechanic said we need to pull the exhaust and possibly heads and see what happened.

Pull the exhaust off, looked with a flashlight into cylinder 8, the head of the valve was broken off from the stem and the stem banged-up the top of the piston. The spark plug head was completely sheared off.

Couple days go by and I was curious about the impeller so I returned to the marine shop and I pulled the raw water pump and lines. I found-a bunch of pieces of broken impeller in the pump housing and in the water line. The actual impeller itself was in perfect condition. The impeller chunks I found must have been left in the line from the old engine and when the mechanic installed the new engine, he never flushed out the lines.

Anyway some more time passes.

The mechanic calls me and said he discovered water that got in the engine from the exhaust and it was the water that caused the valve to break. He discovered that one of the gates on my right exhaust tip that is meant to prevent wake water from backing into the engine was missing, he advised that there was allot more water in the right side were the gate was missing and the right side was the side with the failing cylinder 8

(So)

Mechanic: Is blaming water through exhaust as the cause of the valve failure

Me/I: Believe the engine overheated from the cooling lines being obstructed with impeller chunks and the overheating caused the valve to fail.


Finally getting to the actual question.

1st-------------Is it even possible for water through the exhaust to create valve damage like this as the mechanic is saying???


2nd-----------------If the mechanic is right and water got in through the exhaust causing valve failure, what are the signs to look for????


3rd-----------------If I?m right and the engine overheating caused the valve failure, what are the signs to look for????

 

[Silvertip]

Re: Broken Valve ?? Questions ?? Valve Head Broken Where It Connects To Stem

Water can indeed, and very likely, is the cause of the failure and not the impeller debris. With the gate (flapper) missing water can be sucked backwards into the engine. You cannot see this happening. This is why folks who intend to install high performance camshafts in their engines are advised not to do it. Performance cams make this an even greater possibility. Overheating can "tulip" a valve and it can also contribute to the broken valve. But since the flapper was missing there was nothing to stop reversion (backward flow of water into the engine). Overheating would have sounded the alarm and had you been watching the gauges the rise in engine temp would have been noticed.

 

[Bondo]

Re: Broken Valve ?? Questions ?? Valve Head Broken Where It Connects To Stem

Ayuh,... I have more questions, instead of an answer already....

Like, was there in fact Gas in the oil,..?? you said it Smelled like it....
Where is the fuelpump mounted on this motor,..??

The fact that the Alarm went off, would lead me to believe it's not the missing shutter...
If the missing shutter caused reversion,...
I'd expect to see rust tracks all through that manifold on that side...

 

[jan9898]

Re: Broken Valve ?? Questions ?? Valve Head Broken Where It Connects To Stem

Thanks for both of your replies.

I'm not an engine expert so you must excuse my descriptions; the fuel pump was/is located on the front left side of the engine near the pulleys and belts. I will try to get some pictures uploaded here.
Since it does not seem to be simple to answer let me provide some more information here about what went on during the break-in period of this motor leading up to this event.

During the first water test of the new motor, the temp. Alarm sounded about 3 times over a 4 hour period. The boat ran great with no temperature issues for about an hour then the alarm went off, I shut it down let it cool off. I fired it back up after about 20 minutes or so and went to head back in, as I was headed back in I noticed the temperature was fine so I decided to run the boat for a little longer and after about another hour the alarm came on. This same situation happened one more time. I was fishing and moving to different spots, there was no consistency to the alarm going on, it seemed to occur these three times at random. To elaborate, the first time the alarm came on it was after running non-stop for about 30 minutes. The second time it came on was after sitting for about 40 minutes, the alarm came on 3 minutes after starting the boat.

Took it back to the mechanic, he removed the thermostat and checked it. He said it was absolutely the right thermostat and didn?t know why it over-heated those 3 times. He took a brand new thermostat out of the box, drilled one small hole into it, and re-installed it in the boat.

The alarm never came on again until the day the engine failed completely. One thing I did notice though is that the temperature gauge would constantly shoot up to operating temperature then cool down real fast, it would repeat this up and down over and over, basically the engine was never running at one consistent temperature, but it was never getting hot enough to sound the alarm. I shared this with the mechanics and was told that as long as it wasn?t overheating, it is okay.

The boat ran like this for about 45 more hours until the day it shut-down completely.

Back to the day it broke down???????.I had been running the boat for at least an hour without cutting it off before the engine failed. In my opinion flapper or not, it seems un-likely that water could make its way back in through the exhaust when the engine is running. These are large stainless marine exhaust system with a good riser and straight through the hull, I would think it be difficult for water to migrate back with that amount of exhaust gasses and raw water exiting the hull when the motor is running. I CAN see water migration occurring when the engine is not running and the damage occurring when you fire it up but you would think that an hour?s worth of running which was mostly at idle would have blown any moisture right out.

I also left out one thing, when I got towed back in, a mechanic was on the dock, not the guy who did the engine work. He pulled the dipstick, smelled it, said I had gas in the oil and said seems like a bad fuel pump. I shared this with the mechanics that did the engine work but they dismissed it as the cause of the failure.

I need to take a photo of the fuel pump and maybe someone can tell me how to check it for failures.

Since nobody here is going to be able to see the engine, it?s going to be difficult to say what caused it, water could have caused the damage but more than likely in my opinion it was overheating or something else.

My though is there should be signs if it was water and different signs from overheating.

1. Bondo you wrote ?I'd expect to see rust tracks all through that manifold on that side...?

I can check for this to see, are there any other things I can look that can help me determine water damage VS overheating.

One last thing, I was running at 50MPH when the engine shut down, as I slowed to a stop the wake came up and smacked the rear of the boat when the engine was completely off. In my opinion this was more than likely when the water came in, also when the motor was pulled, any water sitting down in the exhaust would get in when the engine because of the angle the engine is lifted.

Just my thoughts, the signs and clues should give the answer. If it was water I should be able to tell, if it was overheating or fuel pump, I should be able to determine it. I'll also tell you that this is the difference between who pays for the repairs. Flapper and water causing damage would be on my dime, overheating or fuel pump would be on his.

Thanks guys????.

 

[Bondo]

Re: Broken Valve ?? Questions ?? Valve Head Broken Where It Connects To Stem

This new engine was installed after freeze damage from the original motor.

Ayuh,... Are the manifolds the same 1s that Froze,..??
Have they been checked for Cracks,..??

I see no mention of changing the Impeller,...
That's the very 1st thing to do in Any overheat situation...

the fuel pump was/is located on the front left side of the engine near the pulleys and belts.

That's the foreward starboard side corner...
There's no Left side, 'n We don't care which way yer Lookin' at the motor...
I know the fuel pump is mounted there,...
Just need to know if it's Block mounted, or electric, or belt-driven...

If the fuel pump was failing, it could lead to detonation, which could destroy the valves...
Combined with a lack of water flow, or other overheat condition, Detonation would happen even Sooner...

Rust, from reversion, or cracked manifolds would more likely sieze the valve between trips, not runnin' at speed...

During the first water test of the new motor, the temp. Alarm sounded about 3 times over a 4 hour period.

Btw,... For future references, an Overheat is dealt with THEN, Not later...
"Things" don't happen without reason, 'n Never fix themselves....

 

[HT32BSX115]

Re: Broken Valve ?? Questions ?? Valve Head Broken Where It Connects To Stem

Couple days go by and I was curious about the impeller so I returned to the marine shop and I pulled the raw water pump and lines. I found-a bunch of pieces of broken impeller in the pump housing and in the water line. The actual impeller itself was in perfect condition. The impeller chunks I found must have been left in the line from the old engine and when the mechanic installed the new engine, he never flushed out the lines.

Howdy,


The above problem is the direct cause of your overheating problem. If you have power steering and/or an oil cooler, you'll also find those pieces crammed in the oil cooler.!

If your fuel pump is mounted on the engine and it has failed, then that would very well be the direct cause of fuel in the oil.

Pull the exhaust off, looked with a flashlight into cylinder 8, the head of the valve was broken off from the stem and the stem banged-up the top of the piston. The spark plug head was completely sheared off.

Exhaust valve, right?



I think it unlikely that reversion would cause a valve failure.......I suppose it's possible.......I think detonation could also do it.

Was the rebuild some sort of "trick" engine build with a "trick" cam or was everything original marine type?

 

[jan9898]

Re: Broken Valve ?? Questions ?? Valve Head Broken Where It Connects To Stem

BOND-O
You asked :

Ayuh,... Are the manifolds the same 1s that Froze,..?? ----------------No, the new 454 that was installed to replace the original one that had freeze damage was complete. The new 454 was drop-in ready, all exhaust componets were new stainless marine, they make a decent product.

Have they been checked for Cracks,..?-------------I'm not sure whether they have been checked but being 45 hours old, you think they should be OK.

I see no mention of changing the Impeller,...------------The Impeller housing, and impeller was brand new on the drop-in motor as well as all the components/accessories directly bolted to the motor.

 

[jan9898]

Re: Broken Valve ?? Questions ?? Valve Head Broken Where It Connects To Stem

H232

You asked

Exhaust valve, right?------------------I believe so, it?s the smaller of the two right? I will check again and take pictures. Its the only valve I can really see looking through the exhasut ports. I will say that i see the same 1 in ever cylider hanging down, the only difference is number 8 does not have a head on it.

I think it unlikely that reversion would cause a valve failure.......I suppose it's possible.......I think detonation could also do it.

Was the rebuild some sort of "trick" engine build with a "trick" cam or was everything original marine type? -----------------Not sure about any trick cam, I will check it out. I was told the engine produced about 450 HP so if you can only get that out of a carb/ 454 by using a special cam, then I would say yes it does.

 

[Bondo]

Re: Broken Valve ?? Questions ?? Valve Head Broken Where It Connects To Stem

I see no mention of changing the Impeller,...------------The Impeller housing, and impeller was brand new on the drop-in motor as well as all the components/accessories directly bolted to the motor.

Ayuh,... Which is now 45 hours ago...'n it's Overheating...

 

[HT32BSX115]

Re: Broken Valve ?? Questions ?? Valve Head Broken Where It Connects To Stem

I was told the engine produced about 450 HP

Of course, without a dyno check, anyone could say that.

A stock Mercruiser 454 with a carburetor is rated for somewhere around 330 (crankshaft) HP To get more than that you would need to up the compression ratio and/or use a different camshaft and probably rate the HP at a higher RPM than original. (5000 or more) Certainly do-able. people do it all the time.

If you got it hot and it then detonated under a load, it's very possible that you could "swallow" an exhaust valve.......

Its the only valve I can really see looking through the exhasut ports.

Yup. That's an exhaust valve......