Perkins 6.354 overheating incident

I ran the engines for the first time in a month and thought I should exercise 'em a bit, warm 'em up, instead of simply moving from slip to mooring. I headed into a 15kt breeze with minor chop. Chugging along at 1800 rpm, the boat did perhaps in the upper 7's knots, temps reached maybe 200 deg. Increased to 2000 rpm, the boat did into the mid 8's, temps increased slightly to maybe 210. Increased to 2200 rpm, temps to 220 plus. Increased the throttles to maybe 3/4 travel, the port engine topped out at 2350, and the starboard 2400. At wide open throttle, the rpms did not increase further. Speed into the lower 9's, temperature in the port engine crept up to 240, temperature in the starboard crept up a smidge higher and set off the idiot light and alarm.

Perkins' manual says 2800 max rpm for a short time and 2400 rpm continuous.

I backed 'way off the throttles and both engines cooled down.

I would have thought that the cooling system would have coped comfortably with at least the Perkins' 2400 rpm continuous. Water temp upper 70's, air temp upper 80's.

Both impellers are new, all hoses are new; don't know the state of the heat exchangers. Engine hours, supposedly, are 1030, original in 1984.

Do I have something to fix?

Yep, two things to fix: 1, cooling systems including HX's. 2, operator needs some schooling on engine temps.

On these, if you get over 200F back off the power and let them cool down. You do not want to run them over 200F, especially under a heavy load. Should be in the 170-190F range. 240 is way hot.

Ski, thanks! I may have the 'normal' temps-vs-rpms wrong in my memory, but the high end is right, by reference to a picture in the manual.

Ski is right. To amplify a bit;


50/50 glycol coolant boils at 223 and the typical 12 psi pressure cap raises it another 30 degrees. But that is to keep the coolant from boiling and cavitating near the cylinder walls where the temps are much higher. So if the indicated temp (assuming it is right) gets above 200 then back down. Most alarm set points are between 200 and 210.


Also your engine is over propped, so it is producing near full power at 2,400 rpm vs rated 2,800 rpm. If it were propped right, that additional 400 rpm would provide about 20% more cooling due to the pumps running that much faster.


And you almost certainly have a fouled cooling system, probably raw water side.


So, get your prop right (and/or clean the bottom) and clean the cooling system.


David

it would be a good idea to buy a digital infra red heat sensing gun at your local auto parts store or Harbor Freight for about $25.00. Aim the red spot at various places in your cooling system, heat exchanger, temp sensor mount, thermostat housing, front, rear and sides of your engine block and cylinder head etc. and compare that with what your gauges are telling you. The rear of the block and the head will be warmer than the front but there should be no hot spots. If you find a hot spot it obviously indicateds where your problem is located. If the gun reads 180 and the block where your temp sensor mounts reads higher then you have a sender or gauge problem not a cooling system problem.

And while you're fixing (replace or clean) the heat exchangers, be sure and check the complete raw water circulation circuit from raw water pump all the way through to the water injection port at the exhaust elbow. Any restrictions will reduce cooling capacity.

Some ideas;

With the engine at fast idle squeeze the hoses with your fingers. If they're rock hard or ballooning you've got a blockage down stream. If not then I would suspect the water pump. They eventually do wear out. Was the cam and wear plate also replaced?

Check the oil cooler water inlet for debris (broken impeller blades.)

6.354 engines (pre-range 4) had a 1.5 inch bronze coolant pipe which ran between the HX and exhaust manifold, across the back of the engine, which has a couple of bends in it and builds up hard sediment causing partial blockages.

Slag buildup in the exhaust manifold and elbow can also restrict water flow.

My 6.354's run 180 degrees without variation between 2400 - 2800 rpm's. 200 and above is asking for trouble.

Check the ID plate on your injector pump for max engine speed and yes it should turn up to that speed or it's over prop'd.

Ski in NC said:

Yep, two things to fix: 1, cooling systems including HX's. 2, operator needs some schooling on engine temps.

On these, if you get over 200F back off the power and let them cool down. You do not want to run them over 200F, especially under a heavy load. Should be in the 170-190F range. 240 is way hot.

Click to expand...

My favourite engines and I completely agree.

Disconnect every cooling system hose and look for pieces of old impeller blades, bet you find some.

Indeed, much to learn. I've got about 20 hours on these engines and only about ten minutes over 2000 rpm.

Thanks to all of you!

Use a digital photo tach to verify the dashboard tach is correct.

While trouble shooting you might try 70%water 30% AF as water cools better than AF

AF only has 5/8 the BTU heat transfer ability of plain water.

Ski is right at 200F , pull back.

IF the boat operates fine at 7K why would you be operating at FLANK , except as a check for 10-20 seconds?

Will you plan to cruise at 9K?

FF, cruising at 7-8 knots is fine for us. Quieter, more fuel efficient. I had, as described, goosed her up to see what she'd do. No intention to run that way. But, she ought to be able to do what she's designed to do.

Since you folks agree that she failed the test, I've got some work to do before we begin serious cruising. I've got two more sections of hose to replace before all the original hose is gone which will require opening up the cooling system. Easy enough to verify the state of the heat exchangers while they are apart. And the crossover pipe that Eidelweiss mentioned is between those two sections of hose.

Presuming the engines have only the 1030 hours over 32 years, there's been plenty of opportunity for restrictions to build up. Gotta' get that excess cooling capacity back.

you dont tell us if they ever behaved differently.
If they did check prop and bottom for fouling first, before fixing stuff. You always want to keep a record of previous performance as a reference.

All great suggestions above.
You might also want to reset your alarms to go off at a lower temp.
I have the same engines and my alarms are set to go off at around 190*.

Sounds like alarm did not work at all. A good thing to fix. More important than servicing the cooling system.

Bayview, I've got 20 hours on the engines and about 10 minutes over 2000 rpm. Boat was launched in late May after a bottom blister job, new impellers and most hoses. I've got no history on the boat save that she was brought up the ICW from NC to Annap about 6 years ago and was a dock queen since then. She certainly could be foul after these months in Swan Creek, however her rpm/knots was pretty much the same as when we picked her up in May.

fog, good point re: temp alarm set points; I did not know they are adjustable

ski, stbd alarm sounded, and light lit with temp. Both engine alarms sound on startup but that would be oil pressure, not temp.

I guess I could have read the first post!!

But, she ought to be able to do what she's designed to do

Perhaps she is, yours is NOT an industrial engine that can be operated 24/7 at peak load.

That you got to max RPM , and there wasn't a fog of black smoke trailing behind is all you need to know.

IF you worry using a good 2 part engine cleaner , and flush flush flush , then new Anti freez with distilled water.

DONE!