Over heating

[Steve91T]

What!? The main benefit in our cooling systems is "anti-boil" and at 50/50 it raises the boiling point to 265 degrees (I just read that). A lower solution as you suggest lowers the boiling point and gets one closer to spontaneous boiling of the solution in contact with the very hot combustion chamber walls. Poof- instant overheat. Keep it from turning to steam to circulate and cool.

That’s incorrect. The system pressurizes and that’s what raises the boiling point.

 

[Steve91T]

The best for cooling is distilled water and water wetter. That’s what is ran in race cars where antifreeze isn’t allowed.

 

[Began]

The pressure also raises the boiling point as does the coolant. Just look it up. Race cars also dump the mixture after every race....something none of us will do.

 

[Began]

From Valvoline: Coolant 101
What Does Coolant Do for My Engine?
The primary purpose of coolant is transferring heat and preventing engine damage caused by freezing or boiling.


From Caterpillar: Coolants
Cat Coolants provide excellent protection against boiling and freezing to prevent component degradation.

 

[FF]

"Race cars also dump the mixture after every race....something none of us will do. "

The antifreeze is PM to be drained , flushed and changed every 3 years or so.

A bigger personal danger is cars need their brake fluid changed out at intervals because it absorbs water.

If the fluid gets to over 210F, the water changes to steam which is compressible , and the brakes no longer function.

 

[mvweebles]

That’s incorrect. The system pressurizes and that’s what raises the boiling point.

Ummm.....that is not accurate. Coolant has a higher boiling point than water (right graph on attached pic).

Although of lessor interest to this discussion, what's interesting is the freeze point hits an apex at around 65% Ethylene Glycol, then reverses and becomes less freeze-tolerant. I seem to recall something in my chemistry class about eutectic solutions working that way.

https://www.carid.com/articles/antifreeze-explained.html


Peter

 

[Ski in NC]

Would be helpful knowing what engine this is..

A side note: while coolant mix at 50/50 does have a higher boiling point, it also has a lower specific heat, higher viscosity and worse thermal conductivity than straight water. Those factors combined, in some cases, especially if system is near max on the heat transfer rate, straight water can do a better job cooling. The boiling point really only comes into play when over 200F (excluding hot spots) and most engines don't get that high.

I have solved some overheat issues by reducing glycol concentration from 50% to either 33 or 25%, then augmenting corrosion inhibitors. Some engines simply sized their HX's right to the edge, very little margin, and anything reducing effectiveness like fouling or super warm sea temp and it goes over the edge. TSTAT full open and temp still climbs. Less glycol often (not always) fixed it. Must keep mind your freezing situation, of course. Not an issue on southern boats.

 

[IG 30]

Hi Began, There is an overflow tube that was blocked as for the engine it is a 120 hp Lehman, im heading down to the boat later today and will get the model number

 

[SCOTTEDAVIS]

Stop and check if it is really overheating, a bad sending unit or gauge is cheap. Use a heat scanner gun to check several points on the engine and cooling system. You should have one for hourly checks and they are cheap.
Start with easy stuff first, then work up.

If really overheating I suspect water flow issues with raw water system.

 

[menzies]

For about $20.00 you can replace your temp sending unit, then another $20.00 might replace the gauge. Start simple

pete

Coolant is bubbling out the cap so temp gauge is probably accurate.

 

[BruceK]

Coolant is bubbling out the cap so temp gauge is probably accurate.

Maybe, but that`s more likely because the overflow tube in the expansion tank is blocked and the coolant needs to go somewhere. A 4psi cap is an easy target.

 

[Ski in NC]

Got to careful reading too much into bubbling out the overflow tube or from around the cap. Coolant inventory will expand as it warms and this process will continue for several minutes beyond where the coolant temp gauge becomes stable. Coolant elsewhere in the system continues to warm up and expand and the bubbles will persist until all temps in the system are stable.

Gots to give it a good 10-15min steady rpm run at power after temps are stable. If still blowing bubbles then, time to think about head gasket.

 

[Began]

Thanks for helping me learn! A question for IG30- seems a smaller amount of water goes out your exhaust mixer and more out the side? Why would a boat manufacturer not want all the water going out and cooling the exhaust? Easier path is water out the side instead of overcoming exhaust pressure so just seems like a problem waiting to happen. I don't get the reason for it..

 

[FF]

"Why would a boat manufacturer not want all the water going out and cooling the exhaust?"

The water in the exhaust is pushed out the exhaust which takes engine power.

Think of an exhaust brake as found on medium duty trucks .

If it can slow a truck coming down a hill, how do you think it will effect the fuel burn and speed of any boat.

 

[Begorrah]

if you have rodded out the heat exchanger then it sounds like the risers or exhaust elbows if that is what you have. If they are cast iron elbows they could be clogged. Need to pull them and check them out.

 

[Polar777]

Is it possible a bad radiator cap could cause this?

 

[Steve91T]

Is it possible a bad radiator cap could cause this?

Yeah absolutely it could.

 

[Comodave]

Brian told me that my radiator cap was 7 psi. Don’t know if that applies to all Lehmans or not. I have SP225s.

 

[BYNW]

Have you tried replacing the cap? There are cheap infrared thermometers that you can use to find the hot spots in the system.

 

[bluewater1953]

Hi guys here's a situation that I've ran into in the past. On my Yanmar 370 diesel .I had an issue where if I throttled up over 1800 RPM my temperature would eventually go up and sound off the alarm. I went through the entire system from the Seacock intake to the exhaust could not find anything wrong. Prior to this situation I could not get to the boat to service and replace The Saltwater impeller. I had a so-called diesel mechanic install it and charge me a hefty bill prior to this overheating problem what I finally found is the new impeller that was installed was installed improperly with a spring bushing rubbing on part of the impeller. I removed the impeller and kept the bushing shaft stationary and then put rotational pressure on the impeller and found that there was some slippage from the shaft to the impeller where the rubber bonded to the brass shaft. I sent the impeller off to Johnson Manufacturing in Sweden and they reported to me that it was the impeller that was installed improperly causing heat buildup and slippage which resulted in overheating .When I attempted to contact the mechanic he denied everything so did the broker that arranged it.Both worthless crooks and not reputable whatsoever hope this helps someone!

 

[SoWhat]

IG30 - Trickle out the exhaust indicative of low raw water flow. Start at exhaust elbow, disconnect water hose, determine flow.
If good flow then exhaust elbow is suspect. Pull it off and clean/replace it.
If poor flow, go to transmission oil cooler. Disconnect water iinput hose. Check flow. If good, go to heat exchanger. then to oil cooler. Then to raw water pump.
Finally I would pull the exhaust hoses off waterlift muffler, and then check the exhaust hoses.
It's probably not fresh water issue because there is low flow out exhaust.

 

[learjett2]

Don't panic

If this is a Leman as I suspect ignore all the possibilitys!
Talk to a Leman authority, they are different, my 120's would overheat if you opened the tank cap when they were hot, allowing air into the system, you have to let them cool before looking into the tank which everyone does in a survey to check for coolent.
Last I checked they are in Virginia.
Good luck

 

[IG 30]

Hi All, I have had a lot of good information so thanks to you all, Last week I got in contact with a marine mechanic here in Australia and he is the man.. I told him all that was happening and straight away he told me to take the exhaust elbow off and see if it is clear, which I did and it was corroded and 80% blocked, someone had fitted and after market stainless steel elbow, I was able to grab an original cast iron elbow from the USA off him.
I am replacing a few other hoses and once I have everything I will see if that was the issue, everything points to that as there was next to no water coming from the exhaust..
I let you know how I go

 

[IG 30]

Hi All,
Its been sometime since I have been on the forum due to work and other commitments. After sometime and effort I found and solved the overheating issue, A blown head gasket amount other things. The heat exchanger and the two oil coolers were both 80% blocked with what I consider to be the decay of the anodes and of course no maintenance, the exhaust elbow was a stainless steel after market one and was almost 90% blocked, a new genuine cast elbow was purchased, the head gasket had been blown between all cylinders for sometime, the head reconditioning shop had said it had been hot a few times prior to my purchase. The day I had taken her out she finally blew between no5 cylinder and a water jacket, hence why she had compression in the water system.
I removed the head ordered parts from the UK but after 5 weeks waiting I ended up purchasing a good secondhand head and having it fully reconditioned, replaced the heat exchanger and the oil coolers, (oil coolers do not have anodes anymore) put the engine back together and is running beautifully, taking around an hour (18deg water temp) to reach 180c and sits there all day at 8knts.
I brought the boat up by sea from the Hawkesbury river to lake Macquarie on Sunday an absolute beautiful day and a great run. I will say that it was disappointing the previous owner wasn't a bit more honest with the condition and the issues, however in saying that I have learnt so much about the Lehman 2715E engine and the workings of the cooling system and now have a great boat....
It just proves maintenance is a cost saving exercise for trouble free boating...

 

[rgano]

Thanks for the final update. I ran back through all the posts on this because I had two FL 2715Es for 29 years and kept them well serviced with never the problems you experienced. It's nice to look back and see who knew what he was talking about and who was just guessing.

 

[Comodave]

Glad you got it fixed. Should be good to go for quite a while now.

 

[IG 30]

Rgano,...Umm, Take everything with a pinch of salt as they say.....