Perkins 6.354 overheat episode.

Dumb question for the day:

So, out for a joyride on Barnegat Bay, turning 1800 rpm and doing 8kts, calm waters and not much wind. Driving from the flybridge, so cannot watch gauges. After running perhaps an hour, the starboard engine temp alarm sounded. I went down to the helm position and the starboard engines' temp was about 235; the port was a little over 190. Starboard's oil pressure was lower than the port's. I throttled back to idle and put the trans in neutral, thinking that coolant flowing was a good thing. I opened up the floor and went back to see if the starboard had begun cooling down; but no perceptible change. Shut it down. Climbed down into the ER looking for guilty signs. None: coolant in the overflow, water in the strainer, alternator/pump belt intact, no coolant smell, no oil smell, no water or coolant spraying around.

Restarted the starboard engine, in neutral and at idle, and went to see if there was water coming out the exhaust. Can't see either side since the swim platform blocks the view and waves are dancing around.

Went back to the helm and see that the water temp is falling and the light/sounder are quiescent. Put in gear and gradually raise the RPM, temperature continues to drop. Back to 1800 RPM and the temperature drops to normal. Ran gradually up to 2000 and then 2200 RPM; temperature stays normal for the 10 remaining minutes to the Marina's entry channel. Oil pressure came back up to normal as the engine temp fell to normal.

What happened? Did I pick up a plastic bag on the external strainer which dropped off when I shut down?

low oil pressure could just be due to the warmer oil. as it heats, it flows easier (reduced viscosity?) and pressure falls.

as to your overheat issue, sounds like something suctioned to the intake that dropped off when you shut it down. (jellyfish, bag, etc)

Why no gauges on the flybridge?

Wawa bag.

BobH said:

Why no gauges on the flybridge?

Click to expand...

Exactly

Something blocked the intake and was released when the engine stopped. I've seen a piece of plastic film stop a diesel driven jet. Sea grass and kelp is also common blocker.

Maybe check that impeller when you get a chance. Might have burned up a little

Re: gauges on the FB. The Perkins panels supplied with this boat are much simpler than those below. Got a tach, the four idiot lights and alarm sounder, and a couple push buttons. I presume stop and start but w/o a key, why would you want to stop the engine and not be able to silence the alarm?

Sounds like something blocking the intake as others have said.

I keep a laser heat gun on board for back-up.

I guess you had better not proclaim it cured until you run it for another hour since you only ran it for 10 minutes on the way back to your marina & it took an hour for the alarm to sound.
With all of the improvements you've made to your boat, add to your to-do list a set of gauges to the bridge!

Well, ran yesterday for about three hours, no issue, rock steady temperature. Today, overheated after about 45 minutes, and despite shutdown and restart, never cooled down to 'normal'.

Time to open up some pumps... I paid for new impellers on both engines and both raw and coolant pumps in the spring. About 50 hours on those impellers, presuming I actually got them.

Sheesh!

Check the cams that squeeze the impeller. They wear out and the pumps don't pump the volume they should.
If they are old I'll bet they are worn out.

Odd ,how it overheats intermittently. It may well be the raw water pump since it was just serviced. Maybe an intake hose collapsing. Have you scrutinized the fresh water side of the system? It could be as simple as a sticky thermostat.

DHeckrotte said:

Well, ran yesterday for about three hours, no issue, rock steady temperature. Today, overheated after about 45 minutes, and despite shutdown and restart, never cooled down to 'normal'.
Sheesh!

Click to expand...

If not the thermostat or collapsed hose and assuming your pump is delivering enough water, it could be a system blockage. Check the hoses between the raw water pump to oil cooler and to heat exchanger. Squeeze them with the engine off, so you know how they feel, then start the engine, run it up a bit and squeeze them again. If they're rock hard or swollen, then you have a blockage down stream from where you're squeezing. Could be anywhere in the circuit all the way to the exhaust elbow. If its not a range 4 engine, you should have a bronze crossover pipe between the heat exchanger and exhaust manifold across the top of the engine above the bellhousing. They get plugged with a build up of sediment over time. Has the exhaust elbow water injection ports been clean recently?

Debris leftover from previous impeller shreddings can cause havoc on the INTAKE side of the raw water pump between the raw water strainer and the pump.
Pieces that take up residence there get plastered against the pumps intake grate, but fall away when the engine is shut off, so you don't see any blockage when you look at the pump.
This can cause mysterious and intermittent overheat when the rest of the system checks out perfectly.