Reply
 
Thread Tools Display Modes
 
Old 08-16-2014, 08:30 AM   #1
Guru
 
timjet's Avatar
 
Join Date: Apr 2009
Posts: 1,905
Raw Water overheat warning

Looking for advise. Cruising the ICW in S.C. at 1400 rpm I got a raw water temp overheat. The engine is a Cummins 6BT 330 M3 reman with 180 hours. The overheat sensor is a Borel strap type that monitors raw water temp about 1 ft downstream of where the exhaust is mixed with the cooling raw water. Coolant temp indication was normal

I immediately shutdown the engine upon receiving the O/H warning and verified the overtemp with a heat gun. The overheat warning lasted about 5 minutes after the engine was shutdown. I checked the raw water intake strainer for debris but it was clear. About 10 days prior to this leg I had the bottom cleaned and the diver said the engine intakes were so clogged with barnacles he was surprised the engines didnít overheat. He cleaned them and changed several zincs. Subsequently we have run the engines 15 hours since the intakes were cleaned and this incident. Prior to this cleaning the boat bottom had not been cleaned since May.

After verifying the strainer was clear I jumped into the water to attempt to verify the intake was clear but due to the tannin in the water and the very swift current I couldnít locate the intakes. While in the water with both engines running in neutral at idle and then at 1500 rpm, I checked both engines raw water flow out the exhaust and they seemed to be the same.

I continued our cruise with both engines running at 1400 rpm and verified with a heat gun the port engine exhaust hose at the location of the overheat sensor was again starting to rise. I increased rpm to 2300 rpm for about 5 minutes and got no overheat warning. I monitored coolant temp carefully and it was normal. After 5 minutes I reduced rpm to 1400 and checked the exhaust tube at the sensor location. Heat gun read 100 deg. Pretty much the same as the other engine.

We continued on to our destination that day at 1400 rpm, another 5 hours, with no issues and no additional overheat warning.

So what to do.

The black band on the blue tube is the overheat sensor.
Attached Thumbnails
Click image for larger version

Name:	P1060473.jpg
Views:	68
Size:	67.8 KB
ID:	32096   Click image for larger version

Name:	P1060478.jpg
Views:	78
Size:	63.2 KB
ID:	32097  
__________________
Advertisement

__________________
Tim
Tampa Bay
Carver 355 ACMY Twin Cummins Diesels Sold
timjet is offline   Reply With Quote
Old 08-16-2014, 08:35 AM   #2
Guru
 
Ski in NC's Avatar
 
City: Wilmington, NC
Country: USA
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
Posts: 3,890
Rotate the band and sensor a bit. The top of the hose often gets hot at low power due to the water mostly being at the bottom of the hose. Not enough water/exhaust velocity to get things to mix very well. A common issue on this type of exhaust. As long as hose does not get hot enough to degrade, it should be ok. At high power, everything should mix fine and hot spot diminish.
__________________

Ski in NC is online now   Reply With Quote
Old 08-16-2014, 08:44 AM   #3
Guru
 
psneeld's Avatar
 
City: Avalon, NJ
Country: USA
Vessel Name: Freedom
Vessel Model: Albin 40
Join Date: Oct 2011
Posts: 15,937
Quote:
Originally Posted by Ski in NC View Post
Rotate the band and sensor a bit. The top of the hose often gets hot at low power due to the water mostly being at the bottom of the hose. Not enough water/exhaust velocity to get things to mix very well. A common issue on this type of exhaust. As long as hose does not get hot enough to degrade, it should be ok. At high power, everything should mix fine and hot spot diminish.


could also pull the hose and check the mixing hole(s), whole mixer for issues/debris.

Some elbows have a large opening...some tiny holes...not sure of yours.
psneeld is offline   Reply With Quote
Old 08-16-2014, 08:46 AM   #4
Guru
 
ranger42c's Avatar
 
City: Maryland
Country: USA
Vessel Model: 42' Sportfish
Join Date: Aug 2013
Posts: 3,160
Failed raw water pump impeller? Broken vanes impeding raw flow downstream from the pump? Sometimes discharge can look OK, especially at idle, when in fact it's not...

-Chris
__________________
South River, Chesapeake Bay
ranger42c is offline   Reply With Quote
Old 08-16-2014, 09:26 AM   #5
Guru
 
timjet's Avatar
 
Join Date: Apr 2009
Posts: 1,905
Thanks Ski, currently the sensor is at the 3 o'clock position. I'll rotate it lower on the hose. I did notice when taking temp readings during the O/H the temp just before the sensor was 170+ and just after the sensor it dropped to 125.

Psneeld; will consider that if the issue continues and all other possibilities are illuminated.

Chris, I had thought of that. The impeller and pump are Tony's Anthens units and have 180 hrs on them. They should be OK, but if the issue continues and I verify the inlet hole is clear, that will be the next step. My guess is though SKI is right since the temps went way down when I increased rpm. Broken impeller and the problem should have gotten worse.
And during this episode the coolant temp never changed, 185 degrees.
__________________
Tim
Tampa Bay
Carver 355 ACMY Twin Cummins Diesels Sold
timjet is offline   Reply With Quote
Old 08-16-2014, 09:29 AM   #6
Guru
 
bligh's Avatar
 
City: Santa Cruz, CA
Country: USA
Vessel Name: Frisky
Vessel Model: 99 Nordic Tug
Join Date: May 2013
Posts: 1,097
Quote:
Originally Posted by ranger42c View Post
Failed raw water pump impeller? Broken vanes impeding raw flow downstream from the pump? Sometimes discharge can look OK, especially at idle, when in fact it's not...

-Chris
x2
cummins are hard to overheat at idle with or without raw water.
check your impeller.
bligh is offline   Reply With Quote
Old 08-16-2014, 09:30 AM   #7
Guru
 
City: gulf coast
Country: pinellas
Join Date: Jun 2014
Posts: 2,199
Sounds like something is blocking the flow from time to time. Junk or old impeller pieces may block flow then settle down with shut down only to plug up sometime later. Look at the first thing downstream from the pump, trans oil cooler? Then the after cooler then heat exchanger.

Also worth checking the seacock hose for growth if the above easy stuff is not the problem.
bayview is online now   Reply With Quote
Old 08-16-2014, 09:38 AM   #8
Guru
 
City: Carefree, Arizona
Country: usa
Vessel Name: sunchaser V
Vessel Model: DeFever 48
Join Date: Apr 2008
Posts: 6,380
Tim, to be clear, your coolant is not over heating but a hot spot showing up on the exhaust hose? Summer water temps can cause this for me in the PNW mind you I see 150 in the summer vs 130 F in the winter on the one side of a Centek.

But, if your diver saw some buildup underwater, the top holes on elbow may be building up also. Is this a new development?
sunchaser is offline   Reply With Quote
Old 08-16-2014, 10:20 AM   #9
Guru
 
timjet's Avatar
 
Join Date: Apr 2009
Posts: 1,905
Quote:
Originally Posted by bayview View Post
Sounds like something is blocking the flow from time to time. Junk or old impeller pieces may block flow then settle down with shut down only to plug up sometime later. Look at the first thing downstream from the pump, trans oil cooler? Then the after cooler then heat exchanger.

Also worth checking the seacock hose for growth if the above easy stuff is not the problem.
It's relatively easy to check the trans cooler for impeller bits, I'll do that.

Quote:
Originally Posted by sunchaser View Post
Tim, to be clear, your coolant is not over heating but a hot spot showing up on the exhaust hose? Summer water temps can cause this for me in the PNW mind you I see 150 in the summer vs 130 F in the winter on the one side of a Centek.

But, if your diver saw some buildup underwater, the top holes on elbow may be building up also. Is this a new development?
Yes a new development. It could be the warmer water but I've operated the engine the last 130 hrs in warmer temps than current with no issues.

And yes the coolant temps have never changed.

I think you're both saying the same thing and that is to check the hose from the sea cock to the raw water pump for clogging. That will require removing the hose, something I probably can't do. I will however stuff a long rod up into the sea cock and see if anything loosens up when the current abates a bit.
__________________
Tim
Tampa Bay
Carver 355 ACMY Twin Cummins Diesels Sold
timjet is offline   Reply With Quote
Old 08-16-2014, 11:23 AM   #10
Guru
 
Capt.Bill11's Avatar
 
City: Sarasota/Ft. Lauderdale
Country: USA
Join Date: Apr 2014
Posts: 5,422
You could also open each strainer and see if the incoming flow appears the same for each unit.

It may just be time to boil out your coolers to get full water flow back. You can do this without removing the coolers.
Capt.Bill11 is offline   Reply With Quote
Old 08-16-2014, 11:50 AM   #11
Guru
 
hollywood8118's Avatar
 
City: Port Townsend Washington
Country: USA
Vessel Name: " OTTER "
Vessel Model: Ocean Alexander Europa 40
Join Date: Nov 2009
Posts: 1,482
Quote:
Originally Posted by timjet View Post
Looking for advise. Cruising the ICW in S.C. at 1400 rpm I got a raw water temp overheat. The engine is a Cummins 6BT 330 M3 reman with 180 hours. The overheat sensor is a Borel strap type that monitors raw water temp about 1 ft downstream of where the exhaust is mixed with the cooling raw water. Coolant temp indication was normal

I immediately shutdown the engine upon receiving the O/H warning and verified the overtemp with a heat gun. The overheat warning lasted about 5 minutes after the engine was shutdown. I checked the raw water intake strainer for debris but it was clear. About 10 days prior to this leg I had the bottom cleaned and the diver said the engine intakes were so clogged with barnacles he was surprised the engines didnít overheat. He cleaned them and changed several zincs. Subsequently we have run the engines 15 hours since the intakes were cleaned and this incident. Prior to this cleaning the boat bottom had not been cleaned since May.

After verifying the strainer was clear I jumped into the water to attempt to verify the intake was clear but due to the tannin in the water and the very swift current I couldnít locate the intakes. While in the water with both engines running in neutral at idle and then at 1500 rpm, I checked both engines raw water flow out the exhaust and they seemed to be the same.

I continued our cruise with both engines running at 1400 rpm and verified with a heat gun the port engine exhaust hose at the location of the overheat sensor was again starting to rise. I increased rpm to 2300 rpm for about 5 minutes and got no overheat warning. I monitored coolant temp carefully and it was normal. After 5 minutes I reduced rpm to 1400 and checked the exhaust tube at the sensor location. Heat gun read 100 deg. Pretty much the same as the other engine.

We continued on to our destination that day at 1400 rpm, another 5 hours, with no issues and no additional overheat warning.

So what to do.

The black band on the blue tube is the overheat sensor.

A couple things...

Shouldn't the sensor be on the S.S. piping before the silicone (blue) hose? .. the silicone is some what of a insulator and the temp will not be as accurate.

You may have build up inside the hose after the thru hull if the thru hull was as bad as the diver said. Might be time to flush the entire system from the hose at the thru hull through the exchangers with Barnacle Barrier.
I had a similar situation and it was a combo of all the exchangers and the turbo inter-cooler that slowed water flow down enough to cause a overheat at high rpm.
Good Luck
HOLLYWOOD
hollywood8118 is offline   Reply With Quote
Old 08-16-2014, 01:51 PM   #12
Guru
 
psneeld's Avatar
 
City: Avalon, NJ
Country: USA
Vessel Name: Freedom
Vessel Model: Albin 40
Join Date: Oct 2011
Posts: 15,937
I'll let Timjet confirm...but I have read where a company that sells an alarm kit say OK to placing on the rubber (why I have no clue having burnt many a hose on the towboat and know that setup intimately)...I think I also remember reading here someone said they had it on the rubber as OKed buy their company.

The OP said the engine temp never changed (at least that's what I thought) so many suggestions would probably result in an engine overheat...not just an exhaust high temp....no harm in checking though.
psneeld is offline   Reply With Quote
Old 08-17-2014, 06:52 AM   #13
Guru
 
timjet's Avatar
 
Join Date: Apr 2009
Posts: 1,905
Thanks guys for all your help. I checked the tranny cooler and there was no debris there, so I'm going to assume the impeller is OK.

I think SKI's explanation is correct. A hot spot occurred at low water flow and disappeared with increased rpm. The engine never overheated. The coolant temp never changed throughout this incident.

The engine is a reman installed less than a year ago now with 180 hours on it. It's unlikely the cooling system is in need of cleaning and remember the coolant temp is normal according to the gauge.

As far as I know the location of the sensor on the rubber exhaust hose is OK.

SKI's knowledge of the Cummins engines is highly regarded on another forum, so I take his recommendations with great weight. I adjusted the raw water temp sensor lower on the exhaust hose and will monitor it closely. I don't want to chase problems that don't exist.

Thanks again guys, hopefully no more problems.
__________________
Tim
Tampa Bay
Carver 355 ACMY Twin Cummins Diesels Sold
timjet is offline   Reply With Quote
Old 08-17-2014, 04:12 PM   #14
Guru
 
Capt.Bill11's Avatar
 
City: Sarasota/Ft. Lauderdale
Country: USA
Join Date: Apr 2014
Posts: 5,422
You are probably right. But just because the op temp is good does not necessarily mean your getting full water volume flow. Sometimes the last thing in the line of the water flow is the first place the lack of volume will show up.
__________________

Capt.Bill11 is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





All times are GMT -5. The time now is 03:26 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012