3.0GS water intrusion with unclear failure mode

[mnjjansen]

Hi all,



My Glastron 175SE got refitted with an 3.0L GM motor built up from several components of my former engine (GSMBYMCE) as I had severe water intrusion. Essentially we only recovered the electrical harness, had the carb rebuild and replaced all the casting and internals by basically new components. The oldest part had 8 hours usage before I used it for three weeks on holiday.

Nevertheless after 3 weeks of daily usage I detected my so feared white emulsion in the flame arrestor coming out the carb, which I pulled because I had some increased backfiring. The same day I also experienced the engine would start difficult. So I knew, I am in trouble .... again. See some pictures in the attachments.

We pulled the head, much water in the exhaust and some in the rear cylinder (corroded). Just got there, minor corrossion. Oil had a visible but very minor green apperance.

The first time we I had water in, former engine, the gasket was shot between the exhaust manifold and cylinder head. My engines cylinders looked like peanut butter. Obvious case. This time we didn't have a clue as the gaskets didn't shown failure. My mechanic is checking the head if it's still straight and well, that's it. Just put it back together. I'm still concerned. Some observations :

* I am rather certain I didn't suck in water from the exhaust due to waves, sudden stops, rear weight. The riser is significantly above water level. My engine still has the flapper valve installed in the exhaust, we checked and it works fine. That said, nowadays it doesn't get installed (to avoid engine overheating due to valve failure), and actually in my case it makes me think it actually decreased the risk on intake water through the exhaust. I intend to keep 'm in.
* I had regular backfires since I got the boat back after the essentially new engine was installed (the 3 weeks with daily usage). As I had the carb rebuilt this rather pissed me off you can recon. Now I think it already took in some water from the beginning, small amounts at a time.
* Performance wise great those 3 weeks, actually got me 67km/hr @ 4650 rpm WOT which is hitting the top range for my combination. Even the last day but my last 30 minutes he fall back to 4.300 rpm. At home flushing : I have a problem.
* I had a thermstat issue during those 3 weeks, it kept CLOSE and the engine didn't overheat but kept cold for a while. Once I replaced the termstat the engine nicely came on specified temp. between 80-90 degrees celcius. Couple of days after I placed the new thermstat the water intake issue came up. I see no correlation, but what do I know.
* The last 2 days, difficult starting. Crank about 5 times before it went. And then it came up slowly, "like one cylinder didn't join the game" I think afterwards, still I thought I had a carb issue until I found the white stuff in the flame arrestor. Carb. looked clean, but the hose going to the valve cover pulled I saw white stuff on the tule which is actually placed right above the trouble cylinder we found out later after pulling the head.
* When we pulled the head the head gasket didn't show leaks (nor did any other gasket). It did show in the middle a kind of hardening, kind of a glass look, brittle and tough to remove. Though the cylinder and surrounding material at that spot was fine this intriges me. While I thought the engine had been running cold for a while, this might indicate it actually (also) got too warm at an instance ?

Now, I have the Clymer manual which doesn't tell me anything seriously about troubleshooting and which has been declared less then toiletpaper here on the forum I looked around further and found the VP service bulletin considering the flapper valves and more interesting, a Mercruiser service bulletin "gasoline engines and water intrusion". I added the link (below ?).

This article gave me the impression that it might be bad ignition on my rear cylinder and then act as a compressor sucking in the water ? The mechanic I am working with said the chance on this is really, really small. I guess he's right, I didn't have a severe drop out of performance, only the last hour.... but I had backfiring going on for a while.

I started with saying that the mechanical engine parts are basically new. Actually that's a point of concern as casting manufacturing processes are not the most reliable ones. So new castings with cracks doesn't suprise me. The engine block has 8 hours, the exhaust manifold and riser are brand new. So, these need to be tested. My mechanic does this with boiling water... I think it should be air tested (low pressure, LEAK testing ) and or (hydro)tested (LEAK and STRENGTH) with acetone due to viscosity. Hot water ? No clue. Guys. advise here ?

So, still work in progress. Nevertheless, you seeing the observations you might recommend me to look at certain other aspects.

Actually I am doing this to support my mechanic which is a self made man here. Good guy, service focused but he's puzzled as well. I am not a mechanic for sure though I likeD the subject .... the first time ... We consider this a project we do both but in this case he's bearing the warranty. We need to get this tackled because I start losing confidence in just 3.0L GM based engines which I know is not justified considering them being around longer then I am. If I had put in a brand new motor, well in the Netherlands that doesn't come cheap (11-12k euro build-in), so far I paid 3.5k euro so from that point of perspective I can handle the current burden certainly. Help appreciated !

Best regards,
Martijn

ps. the link shows different then supposed. It's this https://www.manifoldwarehouse.com/mes/news/Mercruiser_SB_Water_Ingestion.pdf

 

[Assassin3F]

Your head gasket is brand new correct? It looks a little chewed up on the right hand side...also not sure if the scorch marks on the left are oil or char.

That looks like an overheated gasket to me...the reason it is only on one side? There are two cooling system "zones" or paths in the engine one runs:
from the raw water pump=> to the thermostat housing => then straight to exhaust below the riser.

The other raw water pump=> to the thermostat housing =>circulating pump=>Block=>Head=> thermostat housing=>manifold=>riser=>exhaust.

That second loop only goes to the 'manifold=>exhaust' when the T-Stat OPENS (when the engine warms up). If it does not open at operating temp then your engine will keep on heating up the exhaust manifold while dry until you eat some gaskets...then the water in the jackets will start to boil off and/or over pressurize the jacket and/or run dry and then really seriously overheat melt gaskets etc..

T-STAT stays open then the exhaust is constantly cooled by water and it takes longer to get to operating temp but no biggie...
T-STAT stays closed...bad ju-ju.

NOTE: this will not show up on your dash board temperature gauge. The temp gauge is in the thermostat housing if the T-stat is closed no water enters the exhaust manifold, and no water means no water temperature measurement at the gauge. The Temp sender will eventually start showing an elevated temperature...by then your gasket is smoked and the manifold starts heating up the block which damages the head gasket on the right side first and begins showing up on the temp gauge.

My theory is: The Exhaust manifold ran dry and over heated with the t-stat closed; you fried the manifold gasket, and scorched one side of the head gasket, probably the exhaust elbow gasket as well but unsure. The thermostat housing heated up enough that you knew you had a problem but not enough to show you the full extent of the problem.

Assuming my theory is right

...if it is then all of the below are possible true:
the manifold gasket may be smoked
the exhaust elbow gasket is smoked
Head gasket may or may not be reusable with those scorch marks...

Less likely problems...
valve cover gasket may be smoked or not,
oil pan gasket possibly smoked or not,
circ pump gasket smoked but probably not.

Of these the first three could all potentially lead to the top of the engine filling with water during operation or while sitting. Once you fixed the T-Stat, it opened at operating temp and filled the manifold with the now damaged gasket(s) and it filled up with cooling water.

Additional Notes: When you first get an engine reassembled it makes a lot of sense to run it easy for about 10 hours or so for the parts to wear in...operators manuals will specify a 20 hour break-in period. It is smart to baby an engine for the first bit of time and to service it (change fluids filters etc.) before driving-it-like-you-stole-it

When you reassemble the exhaust with the replacement gasket consider filling the exhaust jacket by disconneting hte hose at the thermostat housing and pouring some water inside. This will help keep the manifold cool the first time you start it up when it is dry and prevent any heat damage to your brand new gasket. Once it has been run in the water or on a hose long enough to open the T-stat the manifold will keep water inside until you winterize it again

Also, the top end of the range for my 3.0L is 4200-4600. This is generally pretty stable across models...if you were rolling at 4650 then you were (possibly) running over the red-line at WOT...not saying that was the main factor since it is only marginally over red-line, but you need to note it...I would probably check a manual to make sure that is within the specified range for your current block...might also want to consider a cooler t-stat but that is more along the lines of an "abundance of caution."

That water you had the boat in looks awesome wish I had been there last weekend.

 

[Assassin3F]

One other note for you...

The cooling water in the block flows from front to rear before entering the head and cycling back to the t-stat housing...by the time it gets to the rear most cylinder in the engine it is already pretty hot...for this reason an overheat condition effects the aft most cylinder first and most.

Just checked you picture down into the manifold...that photo shows the restrictor plate for the exhaust elbow mounted with the opening to the outside of the manifold correct? It is difficult to tell the orientation of the plate in that photo. The VP cooling system diagram shows the opening to the engine block side of the elbow where it will then recycle to the manifold.



Also I don't know much about backfire diagnosis but I would think you might get some pops when you come off of WOT if you were running the engine hot...sudden throttle changes or a hot Head might give you some pre-ignition due to over heat. All of that is pure speculation.

 

[Assassin3F]

One last note: I tried to upload the cooling system diagram but it wouldn't work for me...you can go to the Adults only sticky=>VP info then to #18 and find a service manual for the engine with the diagram.

In your photo it looks like the back of the head gasket is charred and leaking. In another photo it looks like the restrictor plate on your exhaust riser water jacket may be on backwards. According to the cooling system diagram the opening is supposed to be on the engine block side of the riser you may need to check this as it could be the source of the problem...i am not sure.

 

[mnjjansen]

Dear Assassin3F,


Many, many, thanks to you, I totally appreciate you've taken that much effort in supporting me. I've seen your contribution also on another thread of mine, well I only have two, so double thanks. Finally I got a technical correlation between the observations and the eventual failure and your explanation looks much plausible to me, regaining my trust in the overall engine setup. In the meantime the mechanic mentioned that he saw that all cylinders had some water but the last one the most and approx. 1 ltr water from the oil pan. He would send another set of pics which would be informative for this thread also but haven't seen new ones yet. But most important, I'll get your feedback asap to the mechanic for his review, feedback and action. Did you edit something btw as I remember I read (at night I woke up and saw you reply half sleeping) you mentioned about the thermostat mounting in the housing ? That has been done by the dealer, I saw how thin the thermostat valve is in combination with the O-ring mounting. So, they did this for me. That said, it appears the thermostat / -housing is off the old block accidently, failed, and will be replaced as the housing has quite some corrosion (so better house which does also have a new thermostat). I will come back on your other points in more detail after I've gotten the feedback from the mechanic I hopefully can meet today. Thanks !

btw. the water in the Netherlands is always greyish/green with a lot of algae. Not pretty but very nutritious for sea live but here it is a clear salt lake and in a calm bay where it is pretty clear so my son dares to swim in it as now he can see the "killers" coming at him timely, sure my little man. It's called "Het Veerse Meer".

BR,
Martijn

 

[Assassin3F]

I edited it several times last night trying to paste the cooling system diagram into the email and I did have a mention about the supposition of the old thermostat housing being reused...I deleted it cause I wasn't sure if the ultimate problem is the T-stat, the housing, or the manifold water path...I decided that it was probably premature to assume the t-stat housing/t-stat was the cause.

Sorry about the confusion with the edits but I got engrossed while I was running through my manual and it suddenly dawned on me that something looked a little off in your photos.

I would strongly recommend you track down the manual on Boatinfo (there are several with pertinent 3.0L information that have been extremely helpful in diagnosing my own engine problems). Once you have a couple of manuals (you can print them with a free pdf maker so you can refer to them while working on the engine) you will be able to verify your hose setup and part orientation in the manifold.

I have noticed three or four items that need to be checked: 1) make sure all of your hoses are hooked and routed appropriately; 2) Make sure the restrictor plate on your exhaust elbow is oriented in the right manner (you will note when you get the manual that the opening in the plate is supposed to be on the same side of the jacket as return hose to the manifold; 3) make sure your thermostat is correctly installed (it is possible that the T-stat was not your root cause; it is possible that the T-stat siezed because of an overheat condition in the manifold caused by incorrect water flow through the manifold).

Always remember that once the metal surpasses 100 degrees Celsius the water starts to boil and causes atypical water flow due to steam pressure in the water jacket. I think if it were up to me I would swap that T-Stat out for a 160 degree Farenheit model, the engine won't be as efficient but it may buy you a little added insurance...it will also help prevent carb vapor lock with all these different high volatility fuel blends that occasionally cause vapor lock in the fuel line on a hot day.



Confirm that the black staining on your head gasket is a burn mark...if so you should replace that gasket. The water in the oil pan is probably from the water pumping down around the piston or settling down around the piston when engine is off, so you may just have to drain and clean out the mayonaise sludge from the mixture but check the pan gasket on the manifold side of the block and toward the rear of the block for burning or melting, or heat vulcanization/cracking.

 

[mnjjansen]

Dear Assassin3F and rest,


I will certainly try to obtain extra manual information. My mechanic certainly has quite some which he is using for his own repair/overhaul activities.
Your notes to check.
1) certainly, the 3.0GSMBYMCE is quite straight forward with no specific add-ons (open cooling).
2) We will check this absolutely.
3) Good point. Indeed we assume an overheated condition. A new thermstat has been installed by a Volvo Penta workshop and works as you know and I agree with your view that the now working thermstat in combination with the gaskets damaged due to an overheated situation at a certain moment earlier lead to the final failure stage with significant water intrusion.
-) changing the thermstat spec is something to consider, I now intend to rebuild in full intended configuration first, see how it performs. It might be quite possible that the 4650rpm might be a (Faria) gauge positive offset. So let's see what the rebuild brings here and be gentle, which I did, and take time for breaking in.

That all said, the engine has been completely disassembled. And now a big surprise. The crank shaft showed small rusty discolorations on locations that were not custom for him, the mechanic. So he started looking further and (together with a Merc Dealer he knows) they came to the conclusion that the casting part of the oil gallery is failing in the block, thus likely a very fine "hair"crack. According the Merc Dealer this is a known problem and now it comes, which can occur in newly delivered blocks. My block had 8 hours on it. That's kind of scary, meaning a replacement block can have this flaw in it from day 1. The Merc dealer stated they simply replace if they assume the problem is arising from aforementioned. They do not have a Service Bulletin on this casting process flaw.

He showed the rejected block to me and tried to explain the techniques behind the flaw, but honestly got a bit lost there. He also mentioned the white slurrie spit out at a certain location alo pinpointing to the mentioned flaw. I believe he pointed at a small tube which is integral part of the block (with a flat 90 degrees noseflap) correlating to this. Unfortunately I didn't take pictures from that. Perhaps you guys have an idea what's this is all about. Anyhow, the engine block has been replaced already. Luckily the cylinder head is ok. Valves /-seats properly, pistons, rods, oil pan, etc. and all mechanical parts are double checked. I have proper trust in the rebuilding process itself, it's "non proven'' parts I am concerned about and thus needs short interval inspection.

Once it's done I emphasized on some serious test runnning and checking before acceptance. Also the measurements, temp, oil pressure, etc. must be on-spec or no trust. Before season ending I must have evidence the engine is KEEPING functioning properly, then winterize with the absolute certainty not one drip of water is in the engine to start with, especially not in my oil to avoid an issue becomes disaster over time.

Anyhow, I'll keep monitoring the engine rebuild in the first place and if something pops up, I let you know. And if one of you knows a bit more of that oil galery casting flaw that might be very, very, interesting.

 

[mnjjansen]

Dear Assassing3F,

To you special thanks, amazing the effort you have put in for me, going through manuals for me and being out there experiencing/visualizing my engine issue, Totally appreciated and awesome. These boats are our passion and it does get to you when things go bad. I immediately printed your feedback and took a half day off heading to the workshop without appointment and jumped in. Thanks !

BR,
Martijn

 

[Assassin3F]

On the casting process...what I know about casting in general is not specific to engines. But for most part casting they make a mold out of some malleable material in many cases they use a special type of sand with moisture to make it stick together in a form...then crack the form off the mold and pour in molten metal. When they are done they have to wash out the form material and machine specific locations that they can get at like cylinders and crankshaft mounts etc.

I don't know what modern casting processes use but the flaw in the sand casting process is that when forming you tend to get areas where the sand 'sticks' to the form and gets peeled away. You will also from time to time get areas where the moisture will flash to steam and create a small bubble on the internal areas or can create a region that is both too thin and too brittle for the heat and pressure loads of a functioning engine.

Basically, those flaws are termed 'crystallization' or similar. I guess I heard of this phenomena in other forming processes but I thought modern engine manufacturers had corrected the issue...obviously I was wrong if this is a common problem.

 

[mnjjansen]

Well, that's affirmative. Also the metal mass makes a huge difference, pulling heat away quickly causing crimping and cracks depending on riser and feeder locations. That is common, Point is awareness appearently about known casting process performance at a specific spot and knowing poor castings reach markets. Hopefully my new casting hasn't. We only learn by proper testing! This becomes a liability matter. The mechanic has been straight forward. And in the case of rebuilding or remanufacturing an engine, trust in who's handling your engine does count. Thanks.