Ok Merc guys can you shed light on this....

[Lou C]

I was responding to someone who posted up on the hull truth about water in cyls on a Merc 5.0, the owner found that his intake was leaking apparently from a fitting that has a copper tube that connects the intake to the exhaust elbow. Leaking from the inside of the intake, into the cyls on that side. What is the purpose of this tube, is it to circulate hot water under the carb base, or is it exhaust gas?

https://www.thehulltruth.com/boating-forum/1378142-mercruiser-5-0-tks-vortec-water-cylinders-hydrolock.html

I was guessing it was water routed from the area under the 'stat housing, to under the carb base, then up that tube and out the exhaust, but what do I know lol?!
Never saw this before.....

 

[Fun Times]

Hey Lou, are you able to read the comments in the following Mercruiser Facebook group titled What is this flexible metal tube called or where can I order it? I broke it. as some of the posts tends to go over that emissions tube pretty good too,

https://m.facebook.com/groups/6004819312865734/permalink/25493089926945382/?mibextid=wwXIfr

I didn’t fully study the THT thread but I think I saw he pulled the intake and tube off then poured water down the tube and it leaked out the manifold…. I’d think the intake gasket would keep it from leaking into the engine if installed.

 

[Scott06]

I was responding to someone who posted up on the hull truth about water in cyls on a Merc 5.0, the owner found that his intake was leaking apparently from a fitting that has a copper tube that connects the intake to the exhaust elbow. Leaking from the inside of the intake, into the cyls on that side. What is the purpose of this tube, is it to circulate hot water under the carb base, or is it exhaust gas?

https://www.thehulltruth.com/boating-forum/1378142-mercruiser-5-0-tks-vortec-water-cylinders-hydrolock.html

I was guessing it was water routed from the area under the 'stat housing, to under the carb base, then up that tube and out the exhaust, but what do I know lol?!
Never saw this before.....

yes its to heat under the carb for atomization as the vortec head has no exhaust crossover. I am not 100% sure if it takes exhaust gas or water- but thought it was exhaust not water. Definitely doesnt not circulate, assume it gets warm by being connected pathway.

I would think he has a bad intake given that and it must have water in it not exhaust gas.

the aftermarket 4 bbl intakes like I got on my engine from michigan motorz in 2015 do not have this, but both the factory 2 bbl and reman 4 bbls seem to have this in the parts diagram

I'll look in my manual tonight and see if it explains WTF is going on.

he could plug it on both exhaust and intake and run the engine to see if the hydrolock goes away.

 

[Lou C]

I was able to read some of the comments in the Facebook thread and the responder felt it was exhaust gas, which also makes sense, perhaps Merc felt that not having the exhaust cross over in the Vortec design would cause poor fuel atomization in cooler temps. Now the fact that pouring water down the tube had it leaking out of the manifold, really does suggest that some part of it rusted through but that's odd because there was never supposed to be water anyplace other than the cross over under the 'stat housing, correct?

 

[Lou C]

OK thinking about this, it appears that (and someone on the hull truth did suggest this) that the tube that goes from the starboard side exhaust manifold to the intake is some kind of crude EGR system to satisfy some emission standard. So it should be only exhaust gas in that tube running from the manifold to the intake. What may have happened is that the fitting that screws into the exhaust manifold (which should extend into the exhaust gas passage) may have corroded due to salt water use and salt water from the cooling passage is mixing in with the exhaust gas and winding up in the base of the intake manifold, and then it winds up in the cylinders.

 

[Scott06]

OK thinking about this, it appears that (and someone on the hull truth did suggest this) that the tube that goes from the starboard side exhaust manifold to the intake is some kind of crude EGR system to satisfy some emission standard. So it should be only exhaust gas in that tube running from the manifold to the intake. What may have happened is that the fitting that screws into the exhaust manifold (which should extend into the exhaust gas passage) may have corroded due to salt water use and salt water from the cooling passage is mixing in with the exhaust gas and winding up in the base of the intake manifold, and then it winds up in the cylinders.

that may be I couldn't find anything in my PDF engine manual about it.

Was thinking maybe Muc might see it and know