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

[Pmt133]

So I'll preface this with the following:

• Engine is a fresh rebuild, see my other thread for that journey
• Manifold and elbows are brand new Mercruiser
• I checked all sealing surfaces for straightness prior to installing
• This is what happened on the old engine it seems though those had a confirmed gasket leak, I haven't tested these yet now.
• The block and heads were magnafluxed and pressure tested when assembled to find leaks... So it seems isolated but coincidental.

So I am getting ready to pull the engine. Since I have spare gaskets I pulled the manifold/elbows as one piece to make lifting it out easier. Came to fine water in the manifold side of cylinder 5. I was hoping it was from jarring it around removing it but... I drained them and more importantly they were filled with -50 marine non-toxic antifreeze... this liquid was clear not pink. Looking at the photos below it would seem this was happening while running. Seems like an awful lot for condensation too. Am I looking at cracked head and or manifold leak? Based on the pattern this didn't just happen either... Seems to have been occurring since it was rebuilt.

I sprayed and wiped the valves and ports with WD for now to stop it from getting worse. I am working for the next 7 days straight so after that I will try to start poking around. Here are some photos of the port side manifold and head ports, they are paired to each other.










Am I on the right track or should I turn to the long-block itself too?

 

[Scott Danforth]

you have water in the exhaust.

can be from any of the following:
improper timing causing reversion
improper cam causing reversion
leaking manifold to riser joint causing water to run back in
not enough SWL to riser height from factory
too heavy a boat (water logged) causing the boat to sit lower
cracked cylinder head (should have been caught by machinist)
rusted thru cylinder head (should have been caught by machinist)

a 30 second run of the motor will be enough to prevent rusting. just find the source of your water ingress

 

[Pmt133]

you have water in the exhaust.

can be from any of the following:
improper timing causing reversion
improper cam causing reversion
leaking manifold to riser joint causing water to run back in
not enough SWL to riser height from factory
too heavy a boat (water logged) causing the boat to sit lower
cracked cylinder head (should have been caught by machinist)
rusted thru cylinder head (should have been caught by machinist)

a 30 second run of the motor will be enough to prevent rusting. just find the source of your water ingress

I thought about it last night and I'm going to rule out 1-5 for the following reasons:
Timing would show on both banks which it doesn't
Same goes for the cam and more importantly I have the paperwork, it's the correct marine grind for that serial number. Or well... what superceded to it.
The riser joint is odd because it was water. I filled the manifold/riser up with antifreeze a month ago. So it should be pink not clear like it is I would think. And it should've leaked down some just sitting... however I will have to test that.
The riser height again... I'd think I'd see it on both sides not just isolated to one. And more importantly the boat hasn't been in the water in over two months. I winterized it about a month ago. So that water that's in there happened on land running on the trailer.

I'm starting to suspect the heads. It would explain the light vapor I get from the PCV breathers. Though it's not some crazy amount and I'm not picking up anything in the oil. I'm just trying to figure out how it passed a pressure test and inspection during rebuild. That's a lot of water still in there for running on the trailer about 10 minutes before fogging and winterizing but anything is possible.

I have checking and testing to do.

 

[Scott Danforth]

pink antifreeze will turn clear

 

[Pmt133]

I've actually never seen that happen but I will take your word on it. I'll start with the manifolds then.

 

[Lou C]

The manifolds are new Mercruiser but did you check sealing surfaces for flatness & level with a straight edge & feeler gauges? This is especially important with wet joint exhaust. I’d go back & do that. See what Merc’s spec is.

 

[Pmt133]

The manifolds are new Mercruiser but did you check sealing surfaces for flatness & level with a straight edge & feeler gauges? This is especially important with wet joint exhaust. I’d go back & do that. See what Merc’s spec is.

Yeah. They were flat. I don't remember what feeler I was able to slide under (why I didn't mention it further in post 1) but it was near the thinnest I have. But a spec of dirt on a gasket could do it... I'm going to leak check then pull apart and check flatness when I'm off work next week.

 

[QBhoy]

Hi. Is that an engine from a truck or car ? Is it possible that you’re taking water in, as a result of a not suitable cam behaviour?

 

[Pmt133]

Hi. Is that an engine from a truck or car ? Is it possible that you’re taking water in, as a result of a not suitable cam behaviour?

It's a mercruiser that was re-manufactured prior to my buying it used and then I had my shop re-rebuild it because it had water damage. I might lean that way but I'm only seeing it on one and only one bank and I have the receipt for the rebuild and the part number is the correct grind for a marine application. But with the splatter how it is is sure looks like reversion doesn't it....

 

[300sflyer]

This might sound crazy, but one of the byproducts of an internal combustion engine, is water. Have you ever seen dripping water and steam coming from the tailpipe of an automobile? Maybe the same is happening here, and because the manifolds / heads are new, it is showing up as rust on the fresh cast iron inside the manifolds. Just a thought...

 

[Lou C]

You have a good point there; especially on a “cold manifold” system where the manifold/elbow gets water flow all the time. Merc came out with the warm manifold system for this reason where the elbows always get water flow but the manifolds don’t until the stat opens. This keeps the manifolds close to the engine block temp & evaporates any condensation that forms inside the exhaust system.
You can tell if you have the warm mani system if you have separate hoses feeding the elbows & manifolds.
OP which system do you have?
OMC/Volvo always used the simpler cold manifolds system but also used a higher temp 160 stat instead of the 140 used by many Merc engines…..

 

[Pmt133]

It's the cold setup. But it does seem like an awful lot for just condensation and combustion byproducts. And again... why only the one bank of cylinders? I'd almost feel better if both manifolds had water but one is nice sooty black and the other is whats pictured.

I also have the correct 160 degree stat on the engine as well. I believe it is the 3rd design setup?

 

[Lou C]

Yep I think you’re right it would be on both sides if condensation. With it happening on only one side it’s something unique to the exhaust on that side.

 

[300sflyer]

Is one manifold getting more water flow than the other? This can happen if the thermostat housing is partially blocked with rust or other debris.

 

[Pmt133]

I mean a little bit more on the port side (the side in question) but nothing I'd call drastic as far as water flow. Even running hard wide open and doing the feel test by hand they both are warm to the touch but never uncomfortably hot. Like 130-150 on the IR gun with 85 degree water running through them on the bay.

 

[stresspoint]

if i had to take a guess (from seeing this before on a early 5.0 / 307 that sat for some time unused) .
i would be pressure checking the head exhaust port for a corroded area above the valve.
if its not that , then go with a corroded manifold / riser or wet joint leaking.

 

[tank1949]

I thought about it last night and I'm going to rule out 1-5 for the following reasons:
Timing would show on both banks which it doesn't
Same goes for the cam and more importantly I have the paperwork, it's the correct marine grind for that serial number. Or well... what superceded to it.
The riser joint is odd because it was water. I filled the manifold/riser up with antifreeze a month ago. So it should be pink not clear like it is I would think. And it should've leaked down some just sitting... however I will have to test that.
The riser height again... I'd think I'd see it on both sides not just isolated to one. And more importantly the boat hasn't been in the water in over two months. I winterized it about a month ago. So that water that's in there happened on land running on the trailer.

I'm starting to suspect the heads. It would explain the light vapor I get from the PCV breathers. Though it's not some crazy amount and I'm not picking up anything in the oil. I'm just trying to figure out how it passed a pressure test and inspection during rebuild. That's a lot of water still in there for running on the trailer about 10 minutes before fogging and winterizing but anything is possible.

I have checking and testing to do.

Buy some acetone and make a jig or block to seal off ports and pour acetone into both exhaust and then risers. The riser blocks will be the most difficult to build, but if I could fabricate a device, you can too. I suspect y pipe worn shutters are allowing some steam back into head ports. Easy fix!!!

 

[Chris1956]

Gee, I never thought exhaust shutters would let exhaust back into the engine. I had thought they were designed to stop water from entering the engine, when you came to an emergency stop from high speed.

Also, My Mercruiser 4.3LX had broken (and I removed) exhaust shutters for some years. A Merc dealer advised me that they were not necessary, except for paragraph one of this message.

 

[Pmt133]

The shutters are actually brand new... While I don't have experience with it I know of people who did... one more than one occasion I've had people with bad shutters hydro-lock their engine just from being anchored and taking a pounding of waves at the back of the boat with the drive tilted mostly up. The prop hub acted like a funnel... being a deep v and bobbing like a cork in those situations it is pretty easy to happen. Never a problem again after replacing them either... I suppose spacers on the elbow would help as well but I do think there is some reason for them to be there. I don't run bellows, I run the slip exhaust boot on the back so it probably wouldn't be as big an issue.

I'm going to pressure test the block tonight and then Wednesday when I'm off clay off the water ports and pressure test them if the block passes.

 

[Chris1956]

I had the manifold-to-riser joint gasket fail one day in the spring when the boat was on a trailer. This failure hydrolocked the motor.

I removed the spark plugs and blew out the water and squirted oil into the cylinders. Then I pulled the manifold and riser and using a piece of plate glass and some emery paper, trued up the joint. I used some of those thick, silver Quicksilver gaskets on the joint, and never had another issue with it.

I do not think your issue was ever the exhaust shutters. My boat was kept in the saltwater, and faced many storms, w/o any exhaust shutters or water infiltration.