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Axis LS3 melting exhaust manifold


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After riding today on the way back in I was running around 32mph and I smell something burning so I stop and some smoke is coming from the engine bay. I open it up and the starboard side exhaust manifold is melting! While idling it is fine and cruising it seemed to stay at normal temperature. When I opened it up I could see water coming from around the exhaust manifold and the rubber coupling it connects to. The engine is fine and the oil is not milky at all so wtf is going on? Here are some pics of the starboard side compared to port side. Possibly clogged cat?

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Dirty! I would say the raw water isn't being diverted out to your risers correctly... does the rest of the engine cool properly? Is there water in the lines downstream of the thermostat housing?

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See the dealer, there is a calibration update, cross over tube modification and possibly a new heater pump. Should still be under warranty right?

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Dirty! I would say the raw water isn't being diverted out to your risers correctly... does the rest of the engine cool properly? Is there water in the lines downstream of the thermostat housing?

I share the same thoughts. Sounds like not enough cooling water to this manifold. Obviously you do have some or it would be melting under all conditions and not just at WOT. Follow Bobby's advice and post here with the results.

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How exactly does Indmars warranty work? My closest dealer is 2hrs away so oil changes and minor maintenance was always done locally by a "non certified indmar dealer". It's a 2012 with 396hrs.

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Oh and as far as my engine temps they stayed perfectly normal the whole time. I was never given a warning or anything. The smell is what alerted me.

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I can't offer any advice about Indmar's warranty service as I've bought all my boats used. But your exhaust temp is not monitored. Typically the engine temp is monitored at a point close to where the thermostat is in the intake manifold. The temperature there can be much different than in an exhaust manifold.

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How exactly does Indmars warranty work? My closest dealer is 2hrs away so oil changes and minor maintenance was always done locally by a "non certified indmar dealer". It's a 2012 with 396hrs.

It's 3 years from the date of purchase or 5 if you are insured with a Boaters insurance. This was a known concern . Yes, it has to with the amount of water flow to the manifolds. If the update has not been done, this is the first place to start. Mine did it within 20 hrs. Burnt right through the rubber exhaust hoses that attach to the manifolds.

Contact your dealer and ask about the service bulletins related to the ls3 . They should know .

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Is there a way to tell if the cat is damaged? It got hot enough it boiled the paint on the manifold and started to melt the rubber coupling attaching the manifold to the exhaust. Also does anyone have a part number for the water flow kit that indmar put a service bulliten out about? I bought my boat used and my closest dealer treats me like a red headed step child because I didn't purchase from them.

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My only concern is that the boat has almost 400hrs and never had a problem. It has always tried to overheat when first putting jt in but once I open it up a little it is fine the rest of the day. If it's the service bulliten issue wouldn't this have happened a while ago? That's what has me thinking it's something else.

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With regard to checking or cleaning the CAT's.

I had a post a year back searching for reasons why my engine would max out just below the min operating range & posted pics of removing the CAT's.

May help.

http://www.themalibucrew.com/forums/index.php?/topic/46800-2011-rlxi-350-monsoon-replacment-cats/

I ended up removing the manifolds 3 times.

1st time to remove & clean the CATS.

Ended up cleaning the CAT's initially with hot water & dish soap, then used Brake Cleaner, worked a treat, then rinsed again with dish soap to remove any flammable vapors.

Let them dry in the sun & re installed. No noticeable difference.

2nd time, removed the CAT's completely, reinstalled without the CAT's, no noticeable performance difference apart from exhaust sound & smell.

3rd time, reinstalled the CAT's since removal made no performance difference.

The 3 remove & replace experiments were spread over 2 weekends so we could still get a ski in.

Mind you with a center mount removing & reinstalling the manifolds only took about 30 min, removing the CAT's from the manifolds took another 30 min, that Cir-clip is a bugger to remove.

As a thought, check the 02 Sensor post CAT on the heat affected side.

You could swap the post sensors from one side to the other & see if the heat issues moves to the other manifold.

My understanding is the 02 sensor can alter the fuel to attempt to reach an optimal fuel burn, if the sensor is faulty, it could be sending the signal to dump a lot more fuel resulting in the increased heat out that manifold.

I did find awhile back a you tube clip showing how to clean & test the sensor, again brake cleaner worked to clean the sensor.

Edited by Andrew63
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So a little update. I took the water hose off the trans cooler and there was a good bit of junk against the screen. I cleaned it all out then put a garden hose in the outlets hose and flushed it backs towards the pickup on the hull. I hooked everything back up and tried a fake-a-lake for the first time. Started the boat but no suction. Have the boat a few revs like I have to on the lake and still didn't work. I shut the boat off and pulled the impeller which I replaced a month ago. Impeller is perfect. Installed it back and hooked a garden hose to the inlet hose on the impeller. Started the boat and perfect water flow and was pouring out the exhaust like it's suppose to. I shut it off and again back flushed from the impeller inlet out and the water dumps free and smooth out of the hull pickup but I can't get it to suck water from that point. At least not from the fake a lake.

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  • 1 month later...

I have a 2010 mastercraft x2 with indomar 350 engine about 450 hours that just had a complete meltdown of the port manifold. So hot that aluminum melted and went everywhere. Only about 450 hours on engine and no warning. Dealer ran service codes and no record of overheating. Engine out of warranty and being told that they ( the dealer have never seen anything like this before.) I am not a mechanic by any stretch of the imagination, but this does not seem like it should happen. Quite an expensive problem. (and before anybody starts, I know this is a Malibu site and so please hold the Mastercrap bashing) It is the only other report of what sounds to be a similar problem I could find.

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I have a 2010 mastercraft x2 with indomar 350 engine about 450 hours that just had a complete meltdown of the port manifold. So hot that aluminum melted and went everywhere. Only about 450 hours on engine and no warning. Dealer ran service codes and no record of overheating. Engine out of warranty and being told that they ( the dealer have never seen anything like this before.) I am not a mechanic by any stretch of the imagination, but this does not seem like it should happen. Quite an expensive problem. (and before anybody starts, I know this is a Malibu site and so please hold the Mastercrap bashing) It is the only other report of what sounds to be a similar problem I could find.

Wow. That's pretty hot.

First, welcome to the Crew! We don't bash, but we do taunt from time to time. For example, since you are an MC owner I'm sure you'll appreciate me typing this slower so you can understand.... ;)

Now that we have that out of the way, did the dealer mention anything about the other manifold? Was the water blocked on only the one side, or both? Did you run the boat listed for surfing on a regular basis? Did the temp alarm ever sound? Lots of questions....

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The LS3 issue is a well documented one and has been covered by 2 service bulletins (SB2012-3 & SB2012-2)

Units Affected: All 2012 and 2013 Model L96 (6.0L) and LS3 (6.2L) with Tube in Tube
Exhaust Manifolds Before Serial Number 2249300
  1. There have been some reports of these exhaust manifolds and hoses exceeding
    recommended temperature. Indmar has identified an approach to resolve this issue.
    The first step is to change the thermostat housing and reroute the water flow through
    the cooling system. The second step is to replace the exhaust hoses.
  2. Is a calibration update that needs to be completed to the ECU
The meltdown on the 5.7 MC X2 sounds to me like a water circulation issue to that manifold i.e. the water is not getting passed through it for some reason i.e. water hose or passage was blocked, also check the muffler in the exhaust as I have had the baffles fail and block the exhaust to the point where water stops flowing and can hydrolock the engine in some cases
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  • 1 month later...

Dealer said that the other manifold seemed fine...BUT Indmar suggest replacing them both as well as plumbing an extra kit to help cool the manifold. They noted no problems with my cooling system at all. I have read elsewhere that manifold temp is not measured, and my engine never registered an overheat code. I can tell you that it was so hot that I honestly feared a boat fire and feel had I not shut my engine down very quickly that may have happened. Molten aluminum is about 1200 degrees and there is a lot of stuff on that boat that will burn quickly at a much lower temp.

Nonetheless, I find it odd that Indmar makes a "kit" and puts out a "service advisory" for this engine, but not a recall. Why would they do this if there was adequate cooling of the manifold to begin with? They say that there is not a design flaw or a safety issue simply a product enhancement. Owner should cover the expense but why? My boat was out of warranty and so total out of pocket for me was about $6,000.00. I am fortunate and can afford it and nobody got hurt. I am obviously bitter over the situation but more importantly, want to raise awareness about this manifold kit/service advisory. I would love to see all the boat manufactures that use and have used the 5.7 engine come together and insist that indmar make this a recall and not a service advisory before somebody has a boat burn up and before others have costly repairs that seemingly could easily be prevented.

So for those of you who know more about engines, I have a couple questions.

1. Was I really in danger when my manifold got that hot ? (What if we were playing with a wakeboarder behind the boat, music cranked and not just getting going on lake, and had gone for another minute or two)

2. Does it not seem as though if an engine manufacture makes a product and tells dealerships to add it to all engines that come through for service that they realize there may be a problem.

3. If answer to question 2 is yes, then if there is a problem recognized by such a manufacture, should that not be a recall to prevent catastrophic failure as seen in my engine and not a "service advisory " ? If not a recall, what will become of all those people who have engines outside warranty and either self service or have someone besides the dealership service their boat?

justgary, we do surf a fair amount but with stock ballast primarily. No water flow obstruction. Good thermostat, impeller. Interesting only code that registered in system when they checked it was an O 2 sensor.

Interestingly, one other mastercraft owner I know locally with same engine whose manifold got hot and cracked, but dealership says entirely different problem. Also down on Norris lake earlier this year a supra with same engine caught fire. Not sure if I am just looking for smoke where there is no fire ( no pun intended). Or if my concerns are valid enough to raise a stink about.

I am truly disappointed with Mastercraft's handling of the situation, but have to wonder if any of other manufactures would have handled it any differently. I also wonder if I would have known sooner about the $120 kit would I have spent $6000 on my boat. I unfortunately know that answer and that is why I am so frustrated. To term my problem, an out of warranty engine failure seems to over simplify the problem. Kind of like GM saying we have some bad ignition switches and doing nothing else about it. I plan to sell my Mastercraft and have upgraded to a G23 (you can keep typing slowly) but man I love that boat.

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Handmd -

Sorry, I missed the part where you replied to me. Maybe you typed too quickly....

An actual meltdown seems very dangerous on a boat. I would not want to have been around when it happened. I'm surprised that it could happen and still have plenty of cooling going on in the engine. I'm also surprised that you didn't have a fire.

I also agree that they should have sent you a notice of the problem, but I don't know how many of these cases they have had. I hear on the forums that listed surfing can make the problem worse, but that doesn't seem like it is outside of the anticipated use of the boat.

So how did the dealer get to $6k on two manifolds? That seems high, but maybe I'm missing something. Perhaps a friendly call to MC can get them to help you with the cost. You could mention the possibility of a class action against them, and how the public demonstration of melting a manifold in a boat is not going to look good.

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They ended up having to take apart engine, pulling melted aluminum that had went back into one of cylinders. Then new gaskets and putting things back together. I have not dissected the bill thoroughly and I am rounding up. I actually spoke with someone from Mastercraft and he said he was going to look into things and get back to me, but never did. When I spoke to dealership they said he told thme that mastercraft was not going to do anything about problem.

Not really into making threats I am not going to keep and not really the law suit type. Do plan to post some pics of melted manifold and maybe see if a local news channel would have any interest in story.

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