Major problem with 5.7

[justlakinit]

OK...long story short.
1996 5.7 carb motor pre vortec
I have had this boat for approx. 10 years.
Motor went bad approx. 4 yrs ago. When I took the motor apart, it all looked to be in great shape except it had burned a hole in the head between the inner cylinders and the block at the mating surface where the head meets the block.
I replaced with a brand new reman. long block.
Motor worked fine for almost two seasons....then crack in the head and possible crack in the cylinder wall between the inner cylinders again. This time on the opposite side of the last failure.
I replaced the motor again from another vendor and almost two seasons later I am suspecting the same issue again.
I checked the oil a few weeks ago and it looked a little suspect, so I drained it to get a better look at it. It looked a little suspect, but not milky.
I went to pour new oil in the motor and when I pulled the value cap to put the oil it, it looked like a milk shake in there.
I just pulled all the plugs and they all look normal, no water came out of the cylinders, etc.
Getting ready to run a compression test put expect that it will show all cylinders similar.

Additional history:
New exhaust manifolds
new water pump
Completely rebuilt impeller including housing
Boat never got over 185 degrees on the temp gauge.

1st question
I think the boat is getting enough water to satisfy the temp gauge, but I think at high speeds the boat is not getting enough water to cool the block and it is getting hot spots around the center cylinders.
Is this possible?
It can't be a motor issues since this is my third one.
What could be causing this?

2nd question
How can the oil in my valve covers look like a milk shake and the oil in my oil pan look only slightly discolored?

Thanks for the help

 

[alldodge]

OK...long story short.
1996 5.7 carb motor pre vortec
I have had this boat for approx. 10 years.
Motor went bad approx. 4 yrs ago. When I took the motor apart, it all looked to be in great shape except it had burned a hole in the head between the inner cylinders and the block at the mating surface where the head meets the block.
I replaced with a brand new reman. long block.
Motor worked fine for almost two seasons....then crack in the head and possible crack in the cylinder wall between the inner cylinders again. This time on the opposite side of the last failure.
I replaced the motor again from another vendor and almost two seasons later I am suspecting the same issue again.
I checked the oil a few weeks ago and it looked a little suspect, so I drained it to get a better look at it. It looked a little suspect, but not milky.
I went to pour new oil in the motor and when I pulled the value cap to put the oil it, it looked like a milk shake in there.
I just pulled all the plugs and they all look normal, no water came out of the cylinders, etc.
Getting ready to run a compression test put expect that it will show all cylinders similar.

Additional history:
New exhaust manifolds
new water pump
Completely rebuilt impeller including housing
Boat never got over 185 degrees on the temp gauge.

1st question
I think the boat is getting enough water to satisfy the temp gauge, but I think at high speeds the boat is not getting enough water to cool the block and it is getting hot spots around the center cylinders.
Is this possible?
It can't be a motor issues since this is my third one.
What could be causing this?

Your probably in the right area. If your gauge is accurate and you are running at 185, and you have an open cooling system, then the first guess would be hot spots. Do you have open or closed cooling, and what temp thermostat is in it?

2nd question
How can the oil in my valve covers look like a milk shake and the oil in my oil pan look only slightly discolored?

Thanks for the help

I don't see that happening unless you just so happened to notice it when it was first starting. Your engine is running hot in and area and there is a crack. Steam comes out and mixes with the oil. There is not yet enough to make a mess in the pan, and it could be getting wiped clean enough not to notice when the stick goes in and out.

Do you have an alpha or bravo drive, guessing alpha?
Got any pics of your engine hose routing?

 

[Scott Danforth]

the first issue is fire slotting. it happens when the head gasket goes and if not corrected quickly, the slots that you have witnessed occured.

I would assume that the crack is between the center two cylinders? without a picture, I am speculating.

a bit of moisture is common unless the oil gets over 212 to vaporize it. however I think you are closer to the right track.

185 is not high for the motor considering GM runs these at 230F in cars and trucks (for emission redux). However if you do not have adequate flow, or you have sediment in the block, that is another issue. did you verify the block temperature with an IR thermometer?

I am going to assume fresh water cooled.

what brand of manifolds? stock mercruisers? GLM? Barr? Osco?

 

[Bondo]

OK...long story short.
1996 5.7 carb motor pre vortec
I have had this boat for approx. 10 years.
Motor went bad approx. 4 yrs ago. When I took the motor apart, it all looked to be in great shape except it had burned a hole in the head between the inner cylinders and the block at the mating surface where the head meets the block.
I replaced with a brand new reman. long block.
Motor worked fine for almost two seasons....then crack in the head and possible crack in the cylinder wall between the inner cylinders again. This time on the opposite side of the last failure.
I replaced the motor again from another vendor and almost two seasons later I am suspecting the same issue again.
I checked the oil a few weeks ago and it looked a little suspect, so I drained it to get a better look at it. It looked a little suspect, but not milky.
I went to pour new oil in the motor and when I pulled the value cap to put the oil it, it looked like a milk shake in there.
I just pulled all the plugs and they all look normal, no water came out of the cylinders, etc.
Getting ready to run a compression test put expect that it will show all cylinders similar.

Additional history:
New exhaust manifolds
new water pump
Completely rebuilt impeller including housing
Boat never got over 185 degrees on the temp gauge.

1st question
I think the boat is getting enough water to satisfy the temp gauge, but I think at high speeds the boat is not getting enough water to cool the block and it is getting hot spots around the center cylinders.
Is this possible?
It can't be a motor issues since this is my third one.
What could be causing this?

2nd question
How can the oil in my valve covers look like a milk shake and the oil in my oil pan look only slightly discolored?

Thanks for the help

Ayuh,.... Welcome Aboard,..... Have ya ever tried checkin' the spark plug Color, for proper carb tune, 'n fuel delivery,..??
I ask because with yer story, I suspect Detonation is killin' yer motors,...

How often ya changin' the Impeller, 185° sounds Hot to me for a raw water cooled motor,...
Mine rarely to never gets above 165/ 170°, 'n that's with the hammer down, Hard,...

I'm guessin' the sludge in yer valve covers is condensation,....
The valve covers are pretty much the coolest surface in the oilin' system, so that's where the condensate forms,...
Moisture is a by-product of a internal combustion motor,....
When I check my oil, 'n look things over, before goin' out, there's sludge in the valve covers,...
When I return to my dock, they're clean, til the next time I look,...
Most of the moisture has steamed off, but it'll reform by the next trip out,...

 

[justlakinit]

Your probably in the right area. If your gauge is accurate and you are running at 185, and you have an open cooling system, then the first guess would be hot spots. Do you have open or closed cooling, and what temp thermostat is in it?


I don't see that happening unless you just so happened to notice it when it was first starting. Your engine is running hot in and area and there is a crack. Steam comes out and mixes with the oil. There is not yet enough to make a mess in the pan, and it could be getting wiped clean enough not to notice when the stick goes in and out

open cooling
I am not positive, but I think I put a 160 thermo in the last time.
I started becoming suspect of a problem when I notice it taking my boat a long time to reach temp, and then the temp gauge would drop down very quickly when I stopped running and went back down to idle, then would creep back up to around 180 again. This just started happening.
I guess the question is why or how am I getting hot spots???

 

[justlakinit]

Ayuh,.... Welcome Aboard,..... Have ya ever tried checkin' the spark plug Color, for proper carb tune, 'n fuel delivery,..??
I ask because with yer story, I suspect Detonation is killin' yer motors,...

How often ya changin' the Impeller, 185° sounds Hot to me for a raw water cooled motor,...
Mine rarely to never gets above 165/ 170°, 'n that's with the hammer down, Hard,...

I'm guessin' the sludge in yer valve covers is condensation,....
The valve covers are pretty much the coolest surface in the oilin' system, so that's where the condensate forms,...
Moisture is a by-product of a internal combustion motor,....
When I check my oil, 'n look things over, before goin' out, there's sludge in the valve covers,...
When I return to my dock, they're clean, til the next time I look,...
Most of the moisture has steamed off, but it'll reform by the next trip out,...

I just installed a complete rebuild kit (all new housing, etc.) last spring.
Motor usually runs just below 180 on the temp gauge.
Plugs all look pretty identical and normal...I even switched over to a 4 bbl carb on the last motor change.
Motors always run great up until they start doing this. No suet build up around the exhaust, etc.

 

[justlakinit]

the first issue is fire slotting. it happens when the head gasket goes and if not corrected quickly, the slots that you have witnessed occured.

I would assume that the crack is between the center two cylinders? without a picture, I am speculating.

a bit of moisture is common unless the oil gets over 212 to vaporize it. however I think you are closer to the right track.

185 is not high for the motor considering GM runs these at 230F in cars and trucks (for emission redux). However if you do not have adequate flow, or you have sediment in the block, that is another issue. did you verify the block temperature with an IR thermometer?

I am going to assume fresh water cooled.

what brand of manifolds? stock mercruisers? GLM? Barr? Osco?

The cracks in the past have been between the center cylinders.
I have not verified block temp this year, but did test in last summer with an IR and nothing unordinary.
Fresh water cooled
new exhaust manifolds are GLM

 

[justlakinit]

Your probably in the right area. If your gauge is accurate and you are running at 185, and you have an open cooling system, then the first guess would be hot spots. Do you have open or closed cooling, and what temp thermostat is in it?



I don't see that happening unless you just so happened to notice it when it was first starting. Your engine is running hot in and area and there is a crack. Steam comes out and mixes with the oil. There is not yet enough to make a mess in the pan, and it could be getting wiped clean enough not to notice when the stick goes in and out

Running the alpha
what type of pics would you like to see on the hoses?

 

[alldodge]

Running the alpha
what type of pics would you like to see on the hoses?

Thermostat hose routing. I'm wondering if it is not that the thermostat is not installed properly, that the hose routing to the manifolds might be an issue. As you know something is killing the engines and I think it's in the cooling system currently.

 

[justlakinit]

No Title

pretty simple hose routing. One inlet hose goes to thermo, one comes out of thermo to water pump, other two go back to the exhaust manifolds.

 

[JaCrispy]

Have you been using the same intake manifold or did the long blocks come with a new one?

 

[Scott Danforth]

try different manifolds next time. GLM stands for Good Luck Marine

in the t-stat housing, do you have the t-stat sitting in the housing ontop of the little spacer (plastic or copper)?

 

[justlakinit]

Have you been using the same intake manifold or did the long blocks come with a new one?

On the first replacement motor I used the original 2 bbl intake....motor went out. On the second replacement motor, I switched to a marine 4 bbl intake....same result

 

[justlakinit]

try different manifolds next time. GLM stands for Good Luck Marine

in the t-stat housing, do you have the t-stat sitting in the housing ontop of the little spacer (plastic or copper)?

original motor went out using the original OEM manifolds, so I replaced with the new GLM on the first motor replacement.
The t-stat is sitting on the plastic spacer which was also replaced during the last motor replacement. It can only go in the housing one way.

 

[Bondo]

On the first replacement motor I used the original 2 bbl intake....motor went out. On the second replacement motor, I switched to a marine 4 bbl intake....same result

Ayuh,.... So that leaves the fuel tanks, 'n fuel system original,.....

 

[justlakinit]

pulled the heads the other day. Bad head gasket...burned between the two middle cylinders again on the driver side of the boat. So it appears to be a heat issue. My opinion is that although the temp gauge is reading normal temps, it is not getting enough water to keep the middle cylinder cool enough during faster runs.
Can anyone think of a reason that it is not getting enough water....I have replace the whole impeller (housing and all), along with a new water circulation pump...
I am baffled as to why this keeps happening. Maybe the house from the outdrive feeding the motor is cracked or leaking?
Any suggestions?

 

[Bondo]

pulled the heads the other day. Bad head gasket...burned between the two middle cylinders again on the driver side of the boat. So it appears to be a heat issue. My opinion is that although the temp gauge is reading normal temps, it is not getting enough water to keep the middle cylinder cool enough during faster runs.
Can anyone think of a reason that it is not getting enough water....I have replace the whole impeller (housing and all), along with a new water circulation pump...
I am baffled as to why this keeps happening. Maybe the house from the outdrive feeding the motor is cracked or leaking?
Any suggestions?

Ayuh,...... Detonation,.....

 

[justlakinit]

I have never heard any noise engine that would indicate a detonation problem.

 

[JaCrispy]

Is the waterpump on the engine the correct rotation?

 

[Bondo]

I have never heard any noise engine that would indicate a detonation problem.

Ayuh,.... Ya rarely ever do in a boat,.... Spark plug color diagnosis is a sure-fire tool,....