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.

 

[Pmt133]

So I picked up the engine and we probed the area @tpenfield circled above under pressure and got nothing... I was poking around with a screwdriver prior to taking some of those photos... it is possible that is a smear from that....

Anyway, I assembled the engine yesterday and test ran it. Seemed fine. I plan on today to pull the manifolds after it sat and see if there is any moisture. I also converted the engine over to the earlier check ball style hot manifold setup... Being it is a Gen I drive it seems there have been enough reports of issues with the cold manifold setup and mild overheating that I don't want to take a chance. Now everything temp wise is even.

Now my other question.... The serial number range for my engine calls for a 160F thermostat. The warm manifold setup seems to have always used the 140F. The engine has a thunderbolt 5 ignition setup. Does the ignition module use coolant temp for anything? There is a secondary temp sensor that runs to the module... is that just for the alarm? Also... I know under heat you can get some salt crystallization and I would think more so with a 160 thermostat... Should I stick with the 160 I have in it now or swap to a 140?

And all this is pending there is no moisture in the exhaust... otherwise I will be calling the machine shop back.

 

[Lou C]

Well I have never owned a Mercruiser so I can't say why it would be that you'd have overheating with a cold manifold set up, unless Merc's thermostat housing was different flow wise from OMC/Volvo's. My engine originally had the V6 batwings, ran 3 sets of those, at the last replacement I had to convert over to the 2 piece, in all this time (21 years) I never had overheating from the exhaust, or hot exhaust problems, only impeller or other cooling issues. I would THINK that you should have less of a chance of overheating with cold manifolds because you have a constant flow of cool water straight thru the system. So much so that my manifolds run at only about 100* at idle, they might hit 140* max after coming off plane, but never hotter than that.
Whereas with hot manifolds, they don't get water flow till your stat opens, in that case they will always be hotter than 140, I'd guess. I guess we have to see what the other Merc experts here say!
Here's how the OMC/Volvo stat housing flows, this was used on all GM V-6 and V-8s from the 80s, all the way up to the Volvo buy out of OMC and they used the same design till the exhaust changed when the Cat converters were mandated.

 

[Scott06]

So I picked up the engine and we probed the area @tpenfield circled above under pressure and got nothing... I was poking around with a screwdriver prior to taking some of those photos... it is possible that is a smear from that....

Anyway, I assembled the engine yesterday and test ran it. Seemed fine. I plan on today to pull the manifolds after it sat and see if there is any moisture. I also converted the engine over to the earlier check ball style hot manifold setup... Being it is a Gen I drive it seems there have been enough reports of issues with the cold manifold setup and mild overheating that I don't want to take a chance. Now everything temp wise is even.

Now my other question.... The serial number range for my engine calls for a 160F thermostat. The warm manifold setup seems to have always used the 140F. The engine has a thunderbolt 5 ignition setup. Does the ignition module use coolant temp for anything? There is a secondary temp sensor that runs to the module... is that just for the alarm? Also... I know under heat you can get some salt crystallization and I would think more so with a 160 thermostat... Should I stick with the 160 I have in it now or swap to a 140?

And all this is pending there is no moisture in the exhaust... otherwise I will be calling the machine shop back.

The 140 was to help reduce salt and scale crystallization. I believe the 160 was done to improve emissions. I have a warm manifold that was factory with a 160 stat runs about 170-175

I am I fresh so no real scale issue

Personally I would stick w the 160 and use salt away or similar flushing

The warm manifold overheating is only if the check balls allow too much incoming cooling water to bypass the engine block and go directly to the elbows and overboard

 

[Lou C]

I have heard about that crystallization issue, and posted up pix of my old heads, and as far as I am concerned it doesn't happen in my salt water at least for cast iron.
It's not salt, salt dissolves in water, it is calcium as far as I know.
So just for that reason I would not fear using a 160 stat.
Here's the pic, these were used in salt water, moored in salt water for approx 15 years, only replaced due to overheat damage and cooling passages getting eroded by salt, not clogged by deposits. That little bit of white stuff is prob calcium in the cooling passage that dead ended at the rear joint with the intake manifold.

 

[Pmt133]

Well I have never owned a Mercruiser so I can't say why it would be that you'd have overheating with a cold manifold set up, unless Merc's thermostat housing was different flow wise from OMC/Volvo's. My engine originally had the V6 batwings, ran 3 sets of those, at the last replacement I had to convert over to the 2 piece, in all this time (21 years) I never had overheating from the exhaust, or hot exhaust problems, only impeller or other cooling issues. I would THINK that you should have less of a chance of overheating with cold manifolds because you have a constant flow of cool water straight thru the system. So much so that my manifolds run at only about 100* at idle, they might hit 140* max after coming off plane, but never hotter than that.
Whereas with hot manifolds, they don't get water flow till your stat opens, in that case they will always be hotter than 140, I'd guess. I guess we have to see what the other Merc experts here say!
Here's how the OMC/Volvo stat housing flows, this was used on all GM V-6 and V-8s from the 80s, all the way up to the Volvo buy out of OMC and they used the same design till the exhaust changed when the Cat converters were mandated.
View attachment 399019

So on the Alpha, the older ones had lower volume from the water pump. When the Gen II came around, the thermostat housing was redesigned for the cold setup. Thermostat closed, all water goes to manifolds. Thermostat open some goes into the block. The issue becomes that since the manifolds are so free flowing, not enough gets to the block as it just dumps out the manifolds. The check balls allow some water to hit the elbows but once the thermostat opens forces water through the block and through the manifold and restricted elbow gasket... or at least that's what it seems like... There was a thread where bond discussed it but the only one I can find is where he mentions overheating here. Seems to be isolated to a gen 1 issue though and there are more than one thread where people had to use the check ball setup. I don't know.

The 140 was to help reduce salt and scale crystallization. I believe the 160 was done to improve emissions. I have a warm manifold that was factory with a 160 stat runs about 170-175

I am I fresh so no real scale issue

Personally I would stick w the 160 and use salt away or similar flushing

The warm manifold overheating is only if the check balls allow too much incoming cooling water to bypass the engine block and go directly to the elbows and overboard

I was planning on sticking with the 160 and seeing how hot the manifolds and engine gets. If I see 170 or so I won't be too worried. That's what most of the closed cooling half system boats around here run on the manifolds and they last just fine too. Boat isn't we stored so it gets flushed every use anyway. And my ramp is technically on a creek to the river so it gets a decent flush in light brackish at the end of the day anyway lol. I may start doing salt away as well.

 

[Pmt133]

So... I pulled the manifolds off the engine as 1 whole unit to avoid breaking down the riser joint. Every thing was bone dry. No speckled water like last time no rust spots and traces... just a nice lightly sooty manifold port. I'm pretty well convinced that the cold water plus cold manifold setup plus it being only ~30 degrees outside and a relatively short run time caused condensation in the exhaust.

I'm going to continue to monitor and pull the exhaust again after my first sea trial but... for now I'm saying it's plausible it's fixed.

 

[Pmt133]

Haven't pulled the manifolds yet. But so far so good. Been monitoring temps and am seeing ~175F on the manifold and 155F on the elbow. I will probably swap to the 143F thermostat as that is probably pushing it temp wise. But otherwise seems good.

 

[Lou C]

Interesting difference between the Merc and my OMC/Volvo style exhaust. Those run at 95-100* at idle & the hottest they get is about 135/140 after coming off plane. Do you have the warm manifold set up or the cold manifold set up? I’m guessing the former. I recall that Merc came up with that set up to reduce the chance of condensation in the exhaust which can happen esp with extended idling in no wake zones. OMC/Volvo only had the cold set up and I think that’s why most of their engines had a 160 stat; I tried a 140 but the engine took forever to warm up & I did have a bit of condensation in the exhaust….
The only way I found that out was I had to change that dang steering actuator and the only way I could get access was to remove the exhaust on both sides. I was running the 140 stat at the time and had run it earlier that day and was surprised to find a trace of dampness in the exhaust. So after I fixed the actuator I went back to the 160 stat….

 

[cyclops222]

Bad engine rebuilders.

 

[Pmt133]

Interesting difference between the Merc and my OMC/Volvo style exhaust. Those run at 95-100* at idle & the hottest they get is about 135/140 after coming off plane. Do you have the warm manifold set up or the cold manifold set up? I’m guessing the former. I recall that Merc came up with that set up to reduce the chance of condensation in the exhaust which can happen esp with extended idling in no wake zones. OMC/Volvo only had the cold set up and I think that’s why most of their engines had a 160 stat; I tried a 140 but the engine took forever to warm up & I did have a bit of condensation in the exhaust….
The only way I found that out was I had to change that dang steering actuator and the only way I could get access was to remove the exhaust on both sides. I was running the 140 stat at the time and had run it earlier that day and was surprised to find a trace of dampness in the exhaust. So after I fixed the actuator I went back to the 160 stat….

Warm setup, had the cold setup when this happened but per a post from bondo and having a GEN I drive I went to a warm setup. Everything seems to run about the same, block is 160 manifolds 170 elbows get the mixing so they stay cooler. Those temps were in 75 degree water after running 3800 RPM for about 2 hours straight. Seems reasonable and I see no change pushing it.

 

[Lou C]

Hey I just thought of another question for you; you have a remote oil filter mount correct? Did you replace the bypass valve with a higher PSI one to keep the oil from bypassing the filter or is it the standard one (11 psi?). I know some of the truck blocks came with remote oil filter mounts so maybe they came that way. Mine is the original Marine/Industrial unit so I have no idea what they used on those. There isn’t enough access to get under there to replace it so I might just keep using the standard filters for now…

 

[Pmt133]

Hey I just thought of another question for you; you have a remote oil filter mount correct? Did you replace the bypass valve with a higher PSI one to keep the oil from bypassing the filter or is it the standard one (11 psi?). I know some of the truck blocks came with remote oil filter mounts so maybe they came that way. Mine is the original Marine/Industrial unit so I have no idea what they used on those. There isn’t enough access to get under there to replace it so I might just keep using the standard filters for now…

I swapped the bypass valve when I installed mine. It was a lower pressure bypass. I actually have to update the other thread now that photos are back.

 

[Lou C]

Ok thanks
I’ll take a look under there when I change the oil this fall but I don’t think I can bend my 68 year old self into that space well enough to do a good job of it!

 

[Pmt133]

Ok thanks
I’ll take a loom under there when I change the oil this fall but I don’t think I can bend my 68 year old self into that space well enough to do a good job of it!

Mine popped out easy enough with just threading a bolt into it. It would suck to try and tap in the new one installed though. I've done much worse.