Engine overheating

[John Langford]

I blew the belt on my engine yesterday on the last day of a three week cruise and I am not sure if I should be doing further tests to determine if the overheating caused any permanent damage.

I was motoring out to the wind line and I noticed that I had no tach reading and the voltage registered about 12 volts. I went below to check the e-meter and look at the smart charge regulator. When I opened the engine compartment I saw that the belt (Gates Green Line) was shredded and I shut down the engine. The temperature reading was just above 200 degrees at that point and I had coolant and steam bubbling out of the radiator cap. I changed the belt (great fun in a seaway) and two hours later fired the engine up again to get into my slip. It worked fine for over 30 minutes. I have replaced about a cup of coolant. Everything else seems fine. Should I be looking further for problems? BTW, the engine is an M35B.

[SteveLyle]

John,


Sounds like you caught it early enough.  "Just above 200 degree" shouldn't be hot enough to bake the oil or melt anything.  If it ran fine for 30 minutes, then in my opinion you're good to go.

If the engine overheated signifigantly, you should be able to smell it - either from the oil dipstick or just the general aroma of burning rubber and baked oil.

Steve

[John Langford]

Thanks Steve. That is reassuring. The oil looks and smells the same. The only other smell was the unmistakable scent of venting coolant.

One thing that surprised me is that the overheating did not cause the panel buzzer to go off. The buzzer is working but there was not a sound. Do we know at what temperature the buzzer would go off?

[Ray & Sandy Erps]

Hello John,

I agree with Steve, that if the engine still had water to boil you caught it early enough.  If the buzzer you're talking about is the one that goes off when you turn on the key before the engine is started, that might be a "no oil pressure" buzzer.

I overheated my engine this summer, just like you did.  The raw water intake got plugged up with seaweed as we pulled into Squirrel Cove.  We were both focused on selecting a spot to drop the hook and moving at a low idle when the first clue I perceived was the smell of coolant.  We anchored, ran a coat hanger down the thru hull fitting, topped off the coolant level and have since put another twenty or thirty hours on the motor.  

You're motor will be fine.

[Ron Hill]

John : The buzzer trip temp. to sound the alarm is a question for Westerbeake  
I've got a different temp. alarm system on my M25XP.  If I ground out the temp. to sender on the back of the my temp gage, as the gage goes up toward 200 degrees and the alarm sounds.  I also installed a "Hi Temp" press to test switch, so I can check it periodically.  

[John Langford]

Thanks for the further reassurance folks. Changed the oild today and it looked dirty but normal and smelled fine.

I will have to track down the buzzer issue. On the Perkins on my 320, as I recall, the buzzer was supposed to whine continuously for overheating and intermittently for low oil pressure. I guess I just assumed the same in this case. But it could be that there is no overheating warning and the buzzer is only for low oil pressure. If I find out more I will report back.

[John Langford]

I checked the manual and the M35B engine panel buzzer is supposed to beep for low oil pressure and buzz continuously for overheating. I think the reason I didn't hear it when I blew the belt is the buzzer is that it isn't supposed to start buzzing until the water temperature hits 210 degrees. I think I caught the problem when the engine had reached just over 200 degrees.