QSB 5.9 Operating Temp 210°

[Ren Hoek]

A guy I know has a 39 SeaRay with QSB 5.9 380 motors.  At speeds above 18 knots he gets an overheat alarm.  Engines are at 210° at 18 knots cruise speed (verified with laser therm).  His mechanic tells him 210° is normal for that motor and he thinks the overheat alarm is due to a bad sender.  The local Cummins dealer says trucks are running that motor at 210° all day long.  

Is an operating temp of 210° normal for this motor?  210° seems high to me (My QSC 8.3 runs at 171°).  

Topic

[Dave Carlson]

He is crazy. I had that same boat, if it  is a Sundancer, and after servicing everything, as mentioned by Steve, I ran that boat at 25-26 mph all day long and never saw temps above 180. I bet his EGT is off the charts.

[Ren Hoek]

Last I talked to him, the motors are running at 210 – 215 at cruise.  He is convinced that this is normal and has stopped troubleshooting.  

[Bill Desmarais]

This is the QSB 5.9 480 at cruise speed (21-23 mph) last week in my lobster boat (propped max weight to 3440 confirmed).

Always a steady 176F,  2470 rpms, burning 10.5 gals/hr @55% load.

As suggested, a thorough go through of the SWAC and quickly figure out if the engines are cruising in an overload condition.  As Rob suggestioned I’d be no more than idling the engines until resolved 

Hate to see engines burned up needlessly as I did once to a 6BTA 370 many many years ago. 

[Gene Fuller]

He was burning 34 GPH (17 gph per motor) at 2600 rpm

The Cummins spec for that engine is 12.7 gph at 2600 rpm.

[Byron Biggs]

agree

Just to add my 2 cents.  I agree with all of the above.  I have the same engines and after a year with the boat if I ever saw anything above 178(this can be hard to read on gauges) I would do something!

[Ren Hoek]

He was burning 34 GPH (17 gph per motor) at 2600 rpm and 20 KTS Which seems pretty high.  I was burning 17 GPH on my single QSC at 2450 RPM/171 degrees and the same speed with a comparable sized boat and weight.  The guy he talked to at Cummins has him convinced that the engine is designed to run in trucks at 230 degrees all day long.  Hopefully he will get lucky and not suffer serious problems.

[Steve Lewis]

Some other thoughts…….

RH,

Does your friend like his boat and does he intend to keep it for a while?  I ask because there are some other items to explore that could be contributing factors to this heat.  All three of the responses above are pointing at cooling circuit maint.  Specifically the Aftercoolers and Heat Exchangers.  As you will find by searching the forum those are important items for the long term health of these Diesel Engines.  In addition to the cleaning and servicing of these coolers your friend will want to explore the loading of these engines.  Sea Ray is notorious for over propping their engines from the factory.  These 380’s are being asked to do a lot of work to move the 390 Sundancer(I am making an assumption on the model since it was not specifically stated). 

There is plenty written on the forum about this but unless pitch modification has been done by your friend or previous owner then it would be a good idea to get things serviced, clean the running gear and surfaces and then create a performance chart of the current setup then bring those numbers back here to the forum and recommendations can be made about reducing propeller pitch to get the engine loading more inline with what Cummins recommends as opposed to what Sea Ray did at the factory to impress the buyers.

If one combines the cumulative effects of dirty aftercoolers, dirty Heat Exchangers and overloaded engines and it becomes clear how these high temps are appearing.  Clean coolers and appropriate loading will provide a more reliable propulsion system and some peace of mind.

[Fireisland1]

Way high

After 180 you better start doing some serious maintenance 

[Rob Schepis]

Wow, must be 100% non-marine folks he is speaking to.  He needs a real “marine” tech to go through his seawater circuits.  I would not run that boat over hull speed until that is all taken care of.  Let him price a replacement engine these days and I am sure he would agree!

1 user thanked author for this post.

Tony Athens

[Loulouton]

To me 210°F is way to high for a qsb5.9

175- 178°F is the max I get for my twin 425ho. 

[Author]

Replies