What temp is considered Overheating?

[RobH2]

I've searched and read a couple dozen posts and can't find what surely must be here somewhere. What temperature is considered "overheating?"

I've just rebuilt my top end and have raw water cooling so I had the chance to clean out all the block's ports and inside the side water plate. I haven't flushed yet.

The old thermostat was trash so I ran the engine for a week or so without a thermostat and the temp ran at about 130. I recently replaced it with a Moyer aftermarket kit and with the ball valve kit in the vertical hose to the "T". My temperature now hovers between 190 and 210 under power at 1800 RPM. I know most people are seeing 160-180.

Today I'm going to begin diagnosing, flushing, etc.

But, I'd still like to know,what temperature is considered "overheating" where engine damage may begin to occur? What's the highest temperature I can run at without worrying?

[FelicityRebuild]

212 degrees. I think I would start to panic when the water gets to boiling point. That's when the water stops it's cooling effect. The ideal temp is between 160 and 180 degrees, as you point out. Above that you may start to see effects on engine parts.... I think.

[hanleyclifford]

always worried

When it comes to engine temperature, I start "condition yellow" worry at 185 degrees (antifreeze cooling).

[Dave Neptune]

Heat

In salt water I believe once you start going over 160 salts will begin to deposit. One of the biggest advantages with "heat exchanger glycol" cooling is so you can run at higher temps at which wear can be kept to a minimum because the oil will lubricate better.

Dave Neptune

[Baltimore Sailor]

I've searched and read a couple dozen posts and can't find what surely must be here somewhere. What temperature is considered "overheating?"

I've just rebuilt my top end and have raw water cooling so I had the chance to clean out all the block's ports and inside the side water plate. I haven't flushed yet.

The old thermostat was trash so I ran the engine for a week or so without a thermostat and the temp ran at about 130. I recently replaced it with a Moyer aftermarket kit and with the ball valve kit in the vertical hose to the "T". My temperature now hovers between 190 and 210 under power at 1800 RPM. I know most people are seeing 160-180.

Today I'm going to begin diagnosing, flushing, etc.

But, I'd still like to know,what temperature is considered "overheating" where engine damage may begin to occur? What's the highest temperature I can run at without worrying?

I'm probably misunderstanding this, but when you say you have the ball valve kit "on the vertical hose to the 'T'," you do mean "between the 'T' and the thermostat"? 'Cause if it's on the line to the "T" from the pump it's not going to do any good.

[RobH2]

Thanks for the temp info. Yes, BaltSailor, it's where it's supposed to be. I may not have originally described it correctly.

I did a Muriatic Acid flush today and all seems well now. My temp dropped to around 165 instead of peaking over 200. That's good news. Must have had a blockage somewhere that is now dissolved. Also replaced the impeller. It looked OK but did have a permanent bend to all the arms. I'm sure that helps too.

Thanks again,

Rob

[marthur]

I'm glad the problem is resolved.

When we consider cooling water temperatures, don't forget that the cooling water will cool the exhaust and protect the flexible rubber exhaust hose. It has to be well below boiling for that to work.

[Baltimore Sailor]

I, too, have the ball valve in the line to the thermostat, and it's wide open right now. I'm still unable to get the engine much above 150 or so, but that'll change as the Patapsco River/Bay water heats up with summer.

[sastanley]

more numbers for comparison

BS,
The water temp at my dock about 65 miles south of you is almost 60 degrees now...Running the engine last weekend straining against the dock lines, I had to run it very hard to get the temp up...at a lazy 1,000 RPM, it was sitting about 140. If I closed my ball valve to force more water in the block, the gauge went down

[RobH2]

Well, the temp issue raised it's ugly head a day after the initial satisfactory acid flush report. We went sailing last night and while setting the main the engine started to sound odd. I looked down a the temp gauge and it was heading towards the top end of the scale at 240. Yikes, I shut off the engine and it wouldn't stop so I had to shut off the fuel to starve it.

Last night I spend a few hours reading posts here and ran across several talking about impeller parts lodged in the 90 degree water pump exit fitting. I pulled mine...see below what I found:



Put it back together and now have trouble getting over 165. I wish all fixes were that simple... I checked my impeller and it was perfect. I've only had the boat a few months. It's scary to see what surprises previous owners leave us...

[Baltimore Sailor]

Wouldn't stop, eh? I presume that's because the engine was hot enough that the mere compression of the fuel vapor was enough to ignite it (at least partially), and since the engine kept running, the oil sensor kept feeding power to fuel pump, which kept sending fuel to the hot engine...

Maybe this is a case where high-octane fuel would have come in handy!

[sastanley]

wow..go rob...keep up the good work.

[Dave Neptune]

Wouldn't stop

I'd like to chime in here about "engine run on" in an engine such as our precious A-4. With 6.5:1 compression it would be almost impossible to develope enough preassure to cause a "dieseling" type of run-on. If the cylinder was packed with deposits enough to elevate the compression it would probably be nearly impossible to start. The more likely culprit is some of the material deposited in the cylinder has a small area exposed and somewhat insulated from the block material so it does not cool down on the exhaust stroke so when the piston comes up with a bit of fuel the "HOT SPOT" ignites the fuel and the engine will stumble on.
If the ignition is off the fuel pump if it is electric should also be off no matter what the oil preassure switch is doing. With a mechanical pump all the engine needs to do is spin and the fuel will be pumped.
When building some extreme output engines with 12:1 or even higher compression we would spend a great deal of time removing any sharp corners from anything in the cylinder. We would take the sharp corners off of the top of the pistons, and anywhere in the combustion chamber there was a sharp edge we would radius it and this would eliminate "hot spots" within the chamber to protect these expensive beasts. And with all of these efforts and time sometimes a preignition problem would arrise and in most of those cases it would be a sharp corner on a spark plug ground! We would even spend time radiusing the grounds. I have seen the crankshaft literally blown right out the bottom of the engine from preignition both on the track and on the dyno.
As I stated it is probably a dirty cylinder from a poorly tuned combustion chamber, if a deposit starts to break away and just hangs a bit it can retain enough heat to get her lit!
This is one of the reasons I like a fuel shut of as near the carb as possible. In my boat I have a shut off at the tank~~to the~~Racor~~the mech. pump~~in line filter~~PREASSURE GAGE WITH A SHUT OFF VALVE~~to the carb. If something goes arry I can just look and see if the problem may be fuel delivery related ie low or no preassure if all is well then check for spark and if there is spark I immediatly read the plugs.

Dave Neptune

[vabiker23518]

Overheating experience

I have a FWC Atomic 4 in my Columbia 8.7.
During pier side runs this spring, the engine was batching water and looked good. I had replaced the FWC impeller last fall, and the raw water pump this spring.
On our first run out this past weekend, I noticed the water temp went right to 185; we throttled back to idle and continued to the York River. A look at the exhaust showed water batching and appeared normal. Once out of the creek, I went below to determine what the issue was. I noticed the fresh water lines appeared to be slightly collapsed. After securing the engine, I closed the raw water ball valve and pulled the hose from it. I then open the ball valve and water just trickled out. Next, I pulled the 90 degree fitting from the top of the ball valve....found it chock full of brown and green "stuff" that had been sucked into the inlet ball valve. Now there was a nice gush of raw water when the valve was open.
I guess the lesson learned is I should install a strainer, but its worth noting you could have a blockage even if you see water batching at the exhaust. By the way, on the way in the temp stayed between 175 and 180 at cruising speed (sorry, the RPM meter doesn't work).

[etpassgo]

Overheating

According to the Moyer Marine book, normal operating temp for a raw water cooled engine is about 150-170. What worked WONDERS for me is to just bite the bullet and replace the water pump with a new unit. The problem with an old water pump is that it doesn't the proper shaft greasing that it needs and therefore, slows down the pump. Furthermore, the belt will spin around the water pump pulley but not really spin the water pump correctly. While you're at it (getting a new water pump), replace the belt so your late model Atomic 4 get the new pump turning at an adequate rotation to allow it to pump water into the engine.

Also, pull off the side cover on the block and make sure that the T-fitting is pointed in the right direction. The opening should be facing astern and down at about 45 degrees. My first mechanizing put the side cover on upside down and the T-fitting was facing to the front of the boat, this definitely caused a bit of hotter running, not to mention all the gunk that was caked on the T-fitting itself.

Good luck with your work, but please, please, please! Get a new water pump!
It will make all the difference. (when your dentist told you to floss did you listen?)

etpassgo