Manifolds (Trying to figure out what I am looking at)

[Lou C]

I'd say so, still I wonder where the moisture came from? Maybe only condensation? I know that Merc did a few things to try to keep the manifolds hotter to prevent condensation from forming in the exhaust.
The tried the warm manifolds set up were the manifolds don't get water flow till the 'stat opens, then when they changed to the dry joint they used a type of flange on the gasket to keep moisture out.
On my engine which uses the OMC/Volvo set up, the manifolds run cool, like at 95-100* at idle and the most they ever get it to is about 135-140*. What OMC and Volvo seemed to have done, is run a higher temp stat, 160 instead of the 140 that older Mercs used, to achieve the same goal.

so thinking back yours has the cold manifold set up, what temp 'stat are you using? if a 140 maybe try a 160 like the later Mercs used.
On and BTW, the business about a lower temp stat being needed in salt, well mine has had only a 160 and in 20 years of salt water use, when I took it apart, there were no clogged cooling passages, just an even coating of typical cast iron rust. Maybe that's true in Florida, or the Gulf coast but here in the cooler waters of the north east, I don't see it being a problem at least for a cast iron raw water cooled inboard.

At the end of this season I'll probably pull my exhaust to check it, if I do I'll post up pix.

 

[Pmt133]

I'd say so, still I wonder where the moisture came from? Maybe only condensation? I know that Merc did a few things to try to keep the manifolds hotter to prevent condensation from forming in the exhaust.
The tried the warm manifolds set up were the manifolds don't get water flow till the 'stat opens, then when they changed to the dry joint they used a type of flange on the gasket to keep moisture out.
On my engine which uses the OMC/Volvo set up, the manifolds run cool, like at 95-100* at idle and the most they ever get it to is about 135-140*. What OMC and Volvo seemed to have done, is run a higher temp stat, 160 instead of the 140 that older Mercs used, to achieve the same goal.

so thinking back yours has the cold manifold set up, what temp 'stat are you using? if a 140 maybe try a 160 like the later Mercs used.
On and BTW, the business about a lower temp stat being needed in salt, well mine has had only a 160 and in 20 years of salt water use, when I took it apart, there were no clogged cooling passages, just an even coating of typical cast iron rust. Maybe that's true in Florida, or the Gulf coast but here in the cooler waters of the north east, I don't see it being a problem at least for a cast iron raw water cooled inboard.

At the end of this season I'll probably pull my exhaust to check it, if I do I'll post up pix.

Factory stat is actually a 160 on this engine. I will be switching to the warm manifold setup since this is a gen 1 drive. I didn't have any overheat issues yet but it has been reported enough times I am not taking a chance. I will be retaining the 160 as it seems thunderbolt V uses coolant data for something... I am not sure what though.

 

[Pmt133]

So I just got off the phone with the shop. Everything (including manifolds) was pressure tested, inspected, torn down whatever... And there was nothing to be found. They're equally as confused as I am currently but everything checks out.

Was hoping to feel more confident about their findings but I am still a little uneasy. When I go down to pick it up, probably next Friday, I'll dig a little deeper and grab the cam card to confirm that isn't an issue again too. I can't find my copy with my paper work.

 

[tpenfield]

I took a look at the original pictures you posted and noticed something . . . not sure if it has been discussed or perhaps overlooked.


.
Could this be a crack in the exhaust port area of the cylinder head?

Not sure if has been noticed and/or ruled out.

 

[Lou C]

Good catch Ted! Wonder what would happen if you poked that a bit with a small screwdriver or awl?
When I bought the remanufactured heads for mine I got them from a place here on Long Island called Machine World. 7 years later & no leaks. I think they were like $ 275 each….

 

[Pmt133]

I took a look at the original pictures you posted and noticed something . . . not sure if it has been discussed or perhaps overlooked.

View attachment 397628
.
Could this be a crack in the exhaust port area of the cylinder head?

Not sure if has been noticed and/or ruled out.

Good eye. Cylinder 5 which seemed to be near the worst of it. I am hopeful they did everything right but... I'd feel better if that was a crack as odd as it is to say. I'll have to take a look when I go down. Appreciate it.

Good catch Ted! Wonder what would happen if you poked that a bit with a small screwdriver or awl?
When I bought the remanufactured heads for mine I got them from a place here on Long Island called Machine World. 7 years later & no leaks. I think they were like $ 275 each….

Yeah, heads are cheap and accessible around here too. Hell, new from GM they're like $350 a piece.