Seacock strainer

[twistedtree]

Correct - raw water runs first heat exchanger -at least one post mentioned an incident when sand associated with a grounding was only found in the heat exchanger. From the exchanger water enters tge exhaust manifold then out through the exhaust.

I don’t think this is correct. Most manifolds, and I’m nearly certain about the Cummins in question, are coolant cooled, not raw water cooled. In a wet exhaust, raw water gets introduced after the manifold (and turbo if equipped) at the spray ring, which is also where the exhaust transitions form metal because it’s very hot, to hose because it has been cooled by the injected sea water.

 

[twistedtree]

No, manifolds are cooled by raw water which then exits down the exhaust pipe, not by coolant.

I’d be interested to hear of specific engines that have raw water cooled exhaust manifolds rather than coolant cooled. I don’t doubt they exist, but I have yet to encounter one. And I’m 99% certain the Cummins in question is coolant cooled.

As it relates to this incident, a burned manifold, severe loss of coolant, and “smoke” in the er suggests a major overheating event with the cooling system. For that to have been caused by a loss of raw water flow, it would take time to happen. Probably 5-15 min, and maybe more under light engine load. With no raw water flow for that much time, I’m struggling to see how the impeller and exhaust hose immediately down stream of the injection ring would have survived undamaged. That’s what’s not adding up for me, and it suggests some other cause of the overheating.

 

[Bmarler]

I’d be interested to hear of specific engines that have raw water cooled exhaust manifolds rather than coolant cooled. I don’t doubt they exist, but I have yet to encounter one. And I’m 99% certain the Cummins in question is coolant cooled.

As it relates to this incident, a burned manifold, severe loss of coolant, and “smoke” in the er suggests a major overheating event with the cooling system. For that to have been caused by a loss of raw water flow, it would take time to happen. Probably 5-15 min, and maybe more under light engine load. With no raw water flow for that much time, I’m struggling to see how the impeller and exhaust hose immediately down stream of the injection ring would have survived undamaged. That’s what’s not adding up for me, and it suggests some other cause of the overheating.

That was my take in post 12 as well. And the point you made about the manifold being coolant cooled makes sense. If the exhaust manifold was heat damaged, but the exhaust hose at the mixer was not, the raw water flow was never interrupted, or not long enough to be an issue.
I believe what we have is a loss of coolant resulting in overheat.

 

[STB]

From the Perkins Workshop Manual for Diesel Engines circa 1977. Applies to all common variants of the 6.354, 4.07, and 4.08, among many others.

 

[Fleming]

I don't think you're doing yourself any favors by doing your own investigation. The way this is supposed to work is you file an insurance claim, they send a surveyor to supervise the investigation. Everything you touch is just tampering with the evidence. Every statement you make on here will be compared to your statements in the investigation.

Best course of action is always to not touch anything, let the insurance company handle it, fight it afterwards if they don't cover it.

 

[twistedtree]

From the Perkins Workshop Manual for Diesel Engines circa 1977. Applies to all common variants of the 6.354, 4.07, and 4.08, among many others.

Interesting, thanks.

 

[Bmarler]

From the Perkins Workshop Manual for Diesel Engines circa 1977. Applies to all common variants of the 6.354, 4.07, and 4.08, among many others.

I guess you just replace the exhaust manifold and mixing elbow at regular intervals on those.
I think I prefer my coolant cooled cast stainless manifold.

 

[STB]

W.r.t. how the manifold(s) is cooled, I think it is one of those things that has changed from older diesel engines to newer ones.

I haven't done a survey, but it seems to me that a lot of the earlier marinizations just sent seawater through and figured the manifold had enough metal to deal with a ton of corrosion and was easy enough part to swap out as a service item.

Newer engines seem to be more engineered and designed to require less maintenance. They seem to have opted to put the manifold on the closed loop versus the open one. It might also have to do with the fact that newer engines tend to be more efficient and waste less heat. I dunno'.

I looked at moving my 6.354s' manifolds to the coolant loop, but that wasn't meant to be, at least for me. It was a lot more heat to shed an would have required a lot of changes to get enough cooling.

I guess some folks make stainless steel manifolds, but they didn't seem to reach ROI given how long the original.style seem to work in practice.

 

[kapnd]

I once had an overheat with plenty of raw water flowing through the seawater system and out the exhaust pipe.
Turns out that the coolant circulating pump failed!
It had some sort of an anti cavitation plate spot welded to the vanes, the ring came off and got chewed on by the vanes, resulting in bushing failure and subsequent loss of coolant and burned drive belt. (6BT Cummins)
I got home by running raw water through the coolant loop and discharging it overboard, then then a big flush with Salt away after.

 

[twistedtree]

I once had an overheat with plenty of raw water flowing through the seawater system and out the exhaust pipe.
Turns out that the coolant circulating pump failed!
It had some sort of an anti cavitation plate spot welded to the vanes, the ring came off and got chewed on by the vanes, resulting in bushing failure and subsequent loss of coolant and burned drive belt. (6BT Cummins)
I got home by running raw water through the coolant loop and discharging it overboard, then then a big flush with Salt away after.

Something like that would fit all the facts, but probably wouldn't be caused by going over the shoal - at least not in any way I can imagine.


There may well be a valid insurance claim here, but I can understand why the insurance company isn't just writing a check until it's clear there is an insured casualty. So far I'm not seeing it either. Doesn't mean it's not there - just no seeing it yet.

 

[kapnd]

The incident I described was their failure of a poorly manufactured part at a random moment in time, no other factors contributing.
The OPs incident may have been the same, having nothing to do with the grounding.
I also had lots of smoke, due to the circ pump lockup burning the belt.
Here’s what mine looked like when I took it apart.

 

[jimgram]

It’s been about three months since the last post in this thread. In that time, the Insurance company has hired a marine surveyor that specializes in marine loss investigations. Immediately during engine tear down the starboard thermostat was removed and tested. It proved to be ‘stuck shut’. AH – HA! Said the investigators, now about four including the engine tear-down mechanic.

I said “Wait a minute!” – You mean you think a thermostat on a marine engine while cruising at a steady 1200 rpm could suddenly collapse shut? Maybe – but what are the odds of it doing so as the boat crosses thru a shallow shoal kicking up a significant amount of sand/mud behind it, killing the engine, and setting off alarms? And back to the sudden failure of the thermostat while under way – I would think that the thermostat would fail (in the closed position) only after it cooled down and closed. Thermostats are closed by a spring and opened by wax in a closed tube that expands when heated and forces the valve open. Anyone out there with a similar experience with failed thermostats (ignoring the incredible coincidence)?

The investigators are sending the thermostat to a metallurgic lab for analysis, including xray. The biggest issue seems to be the lack of evidence of the grounding – only a small amount of mud or sand in the Groco strainer, exhaust elbow not showing heat damage, the raw water impellers not damaged.

The engine has been removed – a major effort in a Grand Banks 36 Classic. The Cummins 6bt-5.9 engine was totaled – two cylinders galled, valves frozen, crank won’t turn. A recon has been proposed and the cost estimated in excess of $50,000. A hole in the water.

OR, what if the raw water was shut off for a period of 1- to maybe 4 or 5 minutes. I know the exhaust manifold got extremely hot and the engine was toast. Then it's probable that the thermostat was subjected to very high heat. Maybe enough to rupture the wax containment tube and cause the valve plunger to snap closed? I can support the evidence that the coolant over- heated and there wasn't 'much' evidence of raw water stoppage. But raw water had to be effected by passing through a mud or sand shoal.

 

[jimgram]

It’s been about three months since the last post in this thread. In that time, the Insurance company has hired a marine surveyor that specializes in marine loss investigations. Immediately during engine tear down the starboard thermostat was removed and tested. It proved to be ‘stuck shut’. AH – HA! Said the investigators, now about four including the engine tear-down mechanic.

I said “Wait a minute!” – You mean you think a thermostat on a marine engine while cruising at a steady 1200 rpm could suddenly collapse shut? Maybe – but what are the odds of it doing so as the boat crosses thru a shallow shoal kicking up a significant amount of sand/mud behind it, killing the engine, and setting off alarms? And back to the sudden failure of the thermostat while under way – I would think that the thermostat would fail (in the closed position) only after it cooled down and closed. Thermostats are closed by a spring and opened by wax in a closed tube that expands when heated and forces the valve open. Anyone out there with a similar experience with failed thermostats (ignoring the incredible coincidence)?

The investigators are sending the thermostat to a metallurgic lab for analysis, including xray. The biggest issue seems to be the lack of evidence of the grounding – only a small amount of mud or sand in the Groco strainer, exhaust elbow not showing heat damage, the raw water impellers not damaged.

The engine has been removed – a major effort in a Grand Banks 36 Classic. The Cummins 6bt-5.9 engine was totaled – two cylinders galled, valves frozen, crank won’t turn. A recon has been proposed and the cost estimated in excess of $50,000. A hole in the water.

OR, what if the raw water was shut off for a period of 1- to maybe 4 or 5 minutes. I know the exhaust manifold got extremely hot and the engine was toast. Then it's probable that the thermostat was subjected to very high heat. Maybe enough to rupture the wax containment tube and cause the valve plunger to snap closed? I can support the evidence that the coolant over- heated and there wasn't 'much' evidence of raw water stoppage. But raw water had to be effected by passing through a mud or sand shoal.

 

[jimgram]

The claim has been denied - not surprisingly. I've asked for details of the thermostat failure. It looks like I'll need to accept an amazing coincidence. Also, I was mistaken (as a couple of replies affirmed)- the exhaust manifold on a Cummins 6BT 5.9 is not cooled by raw water but by the closed coolant syatem. So there is no evidence of the soft grounding. I have to admit that I have experienced more than one "thump' while motoring down the ICW and even a 'stop and reverse' situation. All I can say is the Groco filter/strainers do a great job (I do carry a pair of spare impellers just in case).

 

[kapnd]

You might be able to get some professional input/advice on sbmar.com.
Tony Athens is a very proficient and experienced Cummins Guru, and is willing to share his knowledge freely!

 

[SteveK]

@twistedtree Looks like you were on the right path to a solution. Who would have thought of a thermostat fused shut though as a source. I cannot imagine the thermostat as the cause, loss of coolant should be first. @jimgram hope you get the report that explains why claim was denied with their interpretation of events.

 

[jimgram]

Thank you for your comments. If I get some answers I'll definitely post. It may help others. I may think twice about when to replace a thermostat.