Cummins 6bta engine temp with smx 160 Thermostats

[Frank Unsicker]

I have a 2002 boat with twin Cummins 6BTA 330 engines.  Both engines have the SMX water pumps with about 20 hours on them.  The engines run at 180 – 185 temp and both engines are within 1 degree of each other.  The factory props were 22×22 but i had the pitch lowered to 20×22 and the engines will run up to 2900 RPM at WOT.  I usually run them at 2000 RPM for most of my boating. 

I want the engines to run cooler so I installed the SMX 160 degree Thermostats on both engines with new antifreeze.  I took the boat out after the installation on 60 degree day and both engines still run at 180 -185 temps.  I have taken the aftercoolers apart and cleaned them,  taken the end caps off the heat exchanges and cleaned them also but this seems to make no difference.

I was hoping the 160 degree thermostats would make a difference in operating temperatures but so far they do not. 

I feel like there must be something else I’m missing that needs to be completed.  Any ideas and help would be appreciated.

Topic

[Frank Unsicker]

Temp issues solved

The temp issue has been solved.   Just follow Tony’s advice and it will work!

I completed the following and all is good:<br />1.  Cleaned the Aftercoolers

2.  Cleaned the Transmission coolers

3.  Cleaned the Heat X.  (I think this was the real problem all the time)

Boat runs around 160,  (Such a simple fix, just had to do all the basic stuff. )

[Antonio Guzzo R.]

Check the thermostat orientation

If your are second guessing, then check the thermostat, it´s a very simple task and sometimes it happens…

[pwrobert]

Another thought

My 6BTA 370s have never seen 180 or above. Typically if idling the temp stays around 140 and at full cruise of 2350 RPM around 165 (occasionally near 170 when the Bahama bank is near 90 degrees). Ialso have the 160 SMX t-stats. If I pull back from cruise when it is reading typically 165- 167F then it quickly go back to 155F withing 1 minute. Never gets above 140F when at the dock. Mine even has the 1.5″ transcooler hoses and raw water heat exchanger hoses not the 1-3/4″ ones. 

Above 2400 up to 3000 still doesn’t reach 185.  Intracoastal here in FL gets abive 90F and ocean 83F or slightly more now.  Boat is setup with triple temp senders and gauges. All agree. 

What size water inlet and hoses do you have installed? Restriction somewhere?

Boat 38Ft, approx 24,000 lbs 22X20 4 blades.

[Frank Unsicker]

Both engines are the same now

Cleaned the Starboard Heat-X and Trans cooler and now both engines max out at 195 at WOT.  I think Im good.  Thanks for the help!

[pwrobert]

Something more?

My 6BTA 370s have never seen 180 or above. Typically if idling the temp stays around 140 and at full cruise of 2350 RPM around 165 (occasionally near 170 when the Bahama bank is near 90 degrees). I have the 160 SMX t-stats. If I pull back from cruise at 167F then it quickly go back to 155F withing 1 minute. never gets above 140F when at the dock. Mine even has the 1.5″ transcooler hoses and raw water heat exchanger hoses not the 1-3/4″ ones. 

Above 2400 up to 3000 still doesn’t reach 185.  Intracoastal here in FL gets abive 90F and ocean 83F or slightly more now.  Boat is setup with triple temp senders and gauges. All agree. 

What size water inlet and hoses do you have installed? restriction somewhere?

[Clark Leighs]

Frank,

One thing I didn’t offer is my tome about engine overheating and possible causes.    It covers a lot  of heating causes.   

Read it through and think about what you have done to your system.    There is more to the cooling system than you have covered and we have discussed. 

  Maybe one or two items have been missed. If you have questions then ask.

The fact that both engines come to virtually the same temperature under the same load is good but it is still work going over.

[Clark Leighs]

I think the 195 at WOT  is what you are going to have to try to live with.

That is likely the temp. the engine will cool to when you run the boat hard, WOT.

I tried to describe the process but I don’t think you get it yet.  As long as the cooling system is in good condition, clean with no water flow obstructions the engine temp. will rise to whatever temperature the cooling medium, you seawater, will cool it to.       At this point it won’t matter that you installed 160 F stats.

If you are still concerned then look up install an overtemp. alarm with a good piezio electric WARBLING sound.     I strongly suggest a warbler.  My experience with single tone units taught me years ago  that the single tone units are not where near as effective.

 THe fact that the engines temp. rose to 195 and then stayed there is a good sign.    If you had a real overheat potential  it would not have stopped rising rather continue upwards untill you backed off the throttle

I also suggest that you record the water temps, the cooling system temps, the boat speed , the boost levels, the EGT , the readings at the stat. housing and so on.       So in the future you can compare todays readings to future readings to monitor any changes.

1 user thanked author for this post.

Frank Unsicker

[Frank Unsicker]

Cleaned Port Heat-X

I cleaned the Port Heat-X and transmission cooler.  This engines runs at 188 degrees when running at 2000 RPM, I then ran it to WOT and it maxed out at 195 degrees and held there.   I brought the Starboard Heat-X home for a good cleaning and will install it next weekend.  (It was 103 degrees outside on this day)

Is the 195 a proper WOT temperature?

[Frank Unsicker]

Winter summer

Winter/Summer is the same.

Sea cocks are fully open

No outside screens on intakes

strainers are clean

 

[Dan]

Removed the After coolers and cleaned them, they were very clean when I removed them for cleaning, there was only one of the tubes that had what looked a small part of a impeller

If a piece of impeller made it to the your aftercoolers some may have made it to the gear/fuel coolers, remove hoses and take a look on the inlet side.

When I have run it up to 2500+ and up it has always run at around 200 degrees

Always? same in winter or summer?

Confirmed inside of the hull intake strainers are clear of marine growth or debris?

Iv’e seen boat yards bottom paint over seawater intake screens and 50% block them

Confirm seacocks are fully open?

 

[Frank Unsicker]

Next trip to the boat

The boat is 3 hours away,  the next trip I will plan on draining the antifreeze and taking the Heat-X and the Trans coolers off,  Ill take them home and give them a good cleaning.  It may be a couple of weeks but I will let you know the results.

[MATTHEW]

Before you get desperate, at least do the basics.  Go through the gear coolers & heat-x’s as you did the aftercoolers.  If there was part of an impeller stuck in the aftercooler, there certainly could be more in the gear cooler etc.  Yes, it’s a pain to drain the coolant and unbolt all this stuff but it doesn’t actually take very long, it’s mindless work that will cure your desperate feelings, and then you’ll know they’re good to go.

[Frank Unsicker]

heat x

I took one of the end caps off a heat exchanger and it did have a piece of a zinc in it but I removed that.  But I have not taken them off and cleaned them.

 

[Frank Unsicker]

Overheat

The after cooler was taken off the boat and taken apart.  It was very clean except one of the tubes had piece of impeller rubber in it.  I used a copper rod to go through each tube and soaked it in cleaner until it looked really clean.  The boat has been in fresh water for that last 17 years before that it was in Portland Maine and stored all winter.  

I have not taken the transmission coolers off and cleaned them, I did not even think of that until we started this process. 

(I’m really second guessing myself now,  is it even possible that I could have put the 160 thermostats in backwards?)  

Getting desperate for something else to try at this point.

[Tony Athens]

I am trying to understand the issue.. 85F seawater?  185F would be about  normal for your engines with a heat-X  and gear cooler of questionable cleanlyness. .

The 160F stats ( that is where they begin to open) are not even fully open until about 175-180F. 

How clean is your HEAT X, and gear cooler? No clue?

You serviced the aftercooler on the bench with the core out, correct?

 

 

[Frank Unsicker]

Yes, I used a Infrared Thermometer to check after I got back to the dock,  It is very close to the temp on the gauges.  It was showing 185 when I get back to the slip and the Infrared gun shows the same when pointed at the thermostat housing.

[MATTHEW]

Sorry if I missed it, but have you confirmed your gauges are accurate?

[Frank Unsicker]

overheat

I already installed new hoses from the strainers to the SMX raw water pump and new hoses from the thru hull to the strainers.   So these are clean.  

 

How do I confirm the trans coolers are not blocked?

[Dan]

Frank,

Check for impeller or other debris ( and marine growth) in the raw water supply hoses to the raw water pump (s) If there is junk in there when you run the engine it will be drawn up to the pump and block water supply, shutdown and it will fall back into the hose and out of sight.

Confirmed raw water intakes are clear?

Confirm trans coolers are not blocked

[Frank Unsicker]

Boat HIstory

I have owned the boat for 17 years on a fresh water lake in Texas.  I normally never run the boat over 2000 RPM’s.  When I have run it up to 2500+ and up it has always run at around 200 degrees,  which I only do for less than 5 minutes due to the temps rising.  I have tried the following:

1.  Removed the After coolers and cleaned them, they were very clean when I removed them for cleaning, there was only one of the tubes that had what looked a small part of a impeller.
2. Installed the SMX 160 thermostats on both engines.  Used the prediluted 50/50 SuperTech Antifreeze Ethylene glycol, diethylene glycol, denatonium benzoate.
3. Installed the SMX water pumps on both engines.  This last weekend I replaced the impellers even though they only had 30 hours on them and they looked new.
4. Changed the props from 22×22 to 20×22.
5. New engine oil and filters
6. New fuel filters
7. Burped each engine per instructions you sent.  When burping I never had the splash occur that was described in the instructions just saw a few bubbles that only occur when I squeezed the hose.  Temps got up to 175 in the slip while burping.  I thought the hose would get hard and there would be some splash with the cap removed but this never happened.  Almost like the thermostat never opened.
8. The water temp is about 85 with the air temp at 100.
9. I tried slowly build RPM’s and I tried just hitting full throttle to get max rpm and both result in the same high temps.  Starboard engines max out at 2975 rpm and Port max out at 2850 rpm.  but both engines have aprox same temps.

I have been searching the internet for ideas and I see that some folks say to clean the transmission cooler but I have not tried this.   Also I saw one post where it said to do a bypass thermostat installed at the heat exchanger but Im not sure how to do that?

 

Any ideas would be helpful.

[Author]

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