210 Cummins 6B temp limits?

[WaterLover]

I have twin Cummins 6B 210HP engines in my "Belle". I have found some old documentation that states if an engine temp gauge indicates higher that 190 degrees then the engine is overheating and should be shut down. On a recent weekend cruise my starboard engine read a bit over 200 degrees but returned down to around 190 after I backed down on the RPM for a while. Should I be concerned? I am just getting to know my boat and am newly learning about my engines. Any insight would be appreciated.
-Annie

[mike66]

Yes you should be concerned enough to check further. I would check:
1. Actual temp of the engine using an IR gun. Very useful tool for about $50 that reads the temp directly off the engine at any point you desire. Maybe the gauge/sender is off. Mine did that recently and it was a poor ground at the gauge that caused a high reading. The gun said the engine was 175, gauge said 200.
2. Loose alternator belt not turning your coolant water pump.
3. Raw water strainer may be clogged.
4. Raw water impeller may be worn or old
5. Heat exchanger may need cleaning
6. Raw water intake hose may be delaminated internally. (Happened on my genset, took a month to discover by accident after tearing my hair out and tearing the engine cooling system apart)
At that point, you've checked out the likely suspects, and may have an engine problem. Most likely one of the above.

P.S. Also if yours is a turbocharged engine, there are heat exchangers that need periodic service, although I can't help with those. Love my 135 Lehman.

[jleonard]

Yes you need to verify that the gage temperature is accurate. I aim my IR temp gun directly on the temp sender. Get very close as distance affects readings as does angle.
200 F won't hurt the engine. But it needs to get fixed. My guess is that the impeller needs to be changed. That's forst up. Next you should take apart the heat exchanger and tranny cooler and clean them out. That is normal mainteneance that should be done every 3 to 4 seasons.
After that follow Mike's list it's pretty complete (however the B 210 does NOT have an aftercooler).
Last but not least grease the cap on the raw water srainer to make sure it seals shut tightly. If it leaks a little air it will not let the raw water pump work properly at higher rpm.
What is your WOT rpm? It needs to be 2600 to 2700 or you are overloaded and that could be a contributor even at lower rpm.
Hope this all helps.

[WaterLover]

Thanks so much for the advice guys. Now if you were only located down here in Charleston I could pay you in beer and pizza to come over and show me some of this stuff. Some I can rule out myself (alternator belts, raw water stainer and cap are all good) but others I have never worked on before (heat exchangers, impellers, tranny cooler). I am guessing the probability is high that it is 4, 5, or tranny cooler causing my problem. I have also noticed that the one engine has much dirtier looking oil than the other and I changed the oil and filters at the same time last March with only light weekend cruising time on them since then.

I will let y'all know. Thanks again.
-Annie

[mike66]

I would got to step 1 first; if the gauge is incorrect then you are chasing your tail doing the others. (Can't tell you have a fever without that thermometer, even if it feels like you do.)

[RobS]

Were these always your temps, or have they climbed over time? Since you have twins, you can switch the gauge wiring and see how they read.. An easy thing to check is the pickup strainer, possible growth, barnacles, etc. Got a mask on-board?

[mike66]

Rob, your advice on switching gauges is a good one in the absence of an IR gun. I know I'm beating a dead horse, but make sure the problem exists before you try to fix it. All the other things on the list are part of normal maintenance and won't hurt to do, but to best budget your time and $$$ make an accurate diagnosis by getting as much information as you can.

[RobS]

Right on mike, agreed. Like messing with your prop and WOT rpms without checking tach accuracy first..

[thomaslong]

I have noticed similar readings on my Cummins 6BTA, with the temp steady at about 190 when I am running at 2250 rpm, then going up to about 200 at 2400 rpm, then right back down to 190 when I drop back to 2250 rpm. The Cummins data sheet I have seems to indicate safe running up to about 205 F. Am I reading this correctly? The data sheet is attached for reference by those who know lots more than me. But I like the idea of putting an IR gun to the engine to get a good reading of the actual temperature.

[RobS]

The IR temperature gun is a handy and fun tool to have on the boat. I have the Extech model 42515 and am very happy with it.

[mike66]

Thomas, I'm not a diesel mechanic, so don't take this as gospel. In general, I think it's okay to get a little bump-up in temp when you run at or near wide open (WOT), as long as the temp stays within normal. Looks like 205 is max normal for your engine. If the temp continued to climb, or increased over time, I would be more concerned. However, as the others have stated, many factors enter in when you push the engine. Bottom growth, propping, raw water flow, air flow through the engine, all have an effect. Yes, getting the IR gun will let you know that your gauge is accurate. For that matter, having your tach checked for accuracy is also not a bad idea (as Rob mentioned above).

[jleonard]

Yes I would not worry about 205 when the engine is "under duress" or after it's been at WOT for a bit. However the original post did not say it was at WOT, rather it was at cruising rpm. That's an issue.

That said, when I had my 6BTA in my Mainship 34 it never showed above 190 even at WOT (2600). Normally it stayed at 180/185 (2000 rpm) unless I was really loafing (1400 rpm) then it would be at 160/170.

Poor raw cooling system maintenance will take the engine out more often than anything else so maintenance is really important. Yes taking heat exchangers off and cleaning them is a PIA at times but it must be done along with regular impeller changes.

[bccanucker]

I have a single Cummins 210 in the Blue Heron. I totally agree with mike66's list especially #5 and also do the tranny oil cooler. Having the heat exchangers cleaned was one of the first things I did when we got the boat in 2010 and then #4 just because. Then one knows where that's at.
The maximum temp I have seen is 180. Mostly we're 170-175. (We pull a 17' Boston Whaler and run around 2000 RPM)
I also highly recommend getting the infa red temp gun. I use mine regularly on the engine, shaft & stuufing box and my Whaler trailer wheels. There is an excellent recent article on this in Passagemaker magazine by Stevie D
Hope this helps

[jleonard]

also do the oil cooler

The engine oil cooler on a 6B is built into the block and uses the antifreeze system for cooling. No maintenance on this is required.
The tranny oil cooler is seperate however.

[bccanucker]

How very right you are. I changed that