Engine running hot - help/advice needed please

[Cpt. Jon]

ok, that is a good thought, I'll keep it in mind, sounds a lot easier than getting to the mixing elbow and to at least check the flow there for restrictions upstream from the elbow.

More than anything I want to determine if it's the raw or fresh water that is the problem and haven't identified that yet... irritating.

By the way, it's an after market fresh water cooler not a yanmar. It's made by Sen Dure http://www.sen-dure.com/ . There is only 1 thermostat on the whole system and after examining the setup I was pleasantly suprised to see that salt water doesn't go into the enigine anywhere... guess I wasn't really clear how it worked before and when this is all over I will have learned a lot about the new engine.

 

[filthy liberal scum]

capt jon;
seems like a lot of questions re 2qm's today.

your in luck! I'm intimately familiar with you setup. i have the exact same on mine. first question is did you replace the sending unit on the engine at the back of the head? i sort of got the impression that you did. converting the engine to fresh water cooling with the sen-dur unit will make it run a little hotter. about 20 to 30degrees. this is not a problem, as it will still only be running at about 130 to 150deg, i know this because i have installed a separate temp gauge on mine and it has a direct readout. however this higher temp will trip the original high temp alarm put on this engine. since these engines were raw water cooled they had to be run at a much lower temp to stop any salt water build up in the engine.

 

[filthy liberal scum]

jon ;
there is one other rhing to check. i had a smallpiece of impeller break off the impeller that circulated the fresh water side. it was stuck in the output side of the pump. very small but enough to restrict flow out of the pump.
Do you have any idea of when this engine was converted? how long it might have been used as a raw water cooled engine. if it was used for a long period of time then i can tell you where to look for a blockage in the engine. this is one that i had problems with prior to converting mine. to fresh water cooling.

 

[Cpt. Jon]

capt jon;
seems like a lot of questions re 2qm's today.

your in luck! I'm intimately familiar with you setup. i have the exact same on mine. first question is did you replace the sending unit on the engine at the back of the head? i sort of got the impression that you did. converting the engine to fresh water cooling with the sen-dur unit will make it run a little hotter. about 20 to 30degrees. this is not a problem, as it will still only be running at about 130 to 150deg, i know this because i have installed a separate temp gauge on mine and it has a direct readout. however this higher temp will trip the original high temp alarm put on this engine. since these engines were raw water cooled they had to be run at a much lower temp to stop any salt water build up in the engine.

I did not do this conversion, it was done right around the time the boat was purchased by the previous owner ~1981 I think. The engine is running about 200F or so and I do not get an alarm.

I just checked the thu hull for the water intake and it seems clear of any obstructions. Unfortunately when I was in the water I forgot to check the output, I will check this a little later. I had previously thought that there was plenty of water coming out of the exhaust, but perhaps its not. If it is though, I will know that it's the freshwater side at least. I would like to be able to eliminate the mixing elbow as a cause because of the cost of replacement, though I don't even want to think about cost of replacement of a heatX.

I am starting to fear an airlock in the fresh water system, don't know how to determine if this is the case or how to bleed it correctly... this overheating might just ruin my weekend. :cussing:

Think I'll go check the freshwater output because I am dying to know which system it's in...

 

[Cpt. Jon]

Ok, was able to stick a bucket under the exhaust from the pier thanks to high tide. The 5 gallon bucket came up 1/2 full after exactly 1 minute. I would estimate between 2.5 and 3 gallons per minute with the throttle in the straight up position, I do not have a tachometer on this boat unfortunately. Is that enough information or knowledge to eliminate the fresh water side?

Also, when I was reading about heat exchangers, I was reading about the yanmar which has a metal impeller that it says rarely fails, but I have NO idea what kind of impeller is in the fresh water side of the heat X that I have Sen-Dure so I don't know if that might be failed or not.

thanks again all for the help so far!

Jon

 

[filthy liberal scum]

jon; this engine doesn't have a metel impeller. the sen-dur unit doesn't either. at least mine doesn't. as a matter of fact both replacement impellers are the same.

 

[Cpt. Jon]

jon; this engine doesn't have a metel impeller. the sen-dur unit doesn't either. at least mine doesn't. as a matter of fact both replacement impellers are the same.

that's great news, when I ordered my last impeller, I ordered two... will check that out shortly. I'm guessing the pump for the sen dure unit is going to look similar to the other than.

will report back.

 

[Cpt. Jon]

Jeez, wish I would have known it was a rubber impeller and not the metal one that the repair manual said it would have and rarely be the problem...

Looks like the engine is now running at about 150F according to the temp guage, I don't know if that exactly right or not. I looked at an infrared temp gun at advanced auto and thought 50 bucks was a little rich for my blood right now all things considered. The bad news is that of six impeller blades, only one was attached and I recovered, one in the housing, one in a hose. I took the hoses apart up to the thermostat and didn't find the others. So now I have a new problem, I have pieces of rubber somewhere in the system. I want to replace all the coolant at some point soon anyway and guess that I will need to figure out how I am to flush the system and find those other pieces of rubber. After the thermostat is the hoses go to the hard to reach spot behind the water heater and then back to the heat X and it starts all over again. So I'm not out of the woods yet and again, more assistance is always appreciated!

Capn Jim, thanks for pointing out that I was wrong about the fresh water impeller :dance:

 

[MoonSailer]

I searched for the cause of my overheating for a couple of years or longer. Could not find the problem so ran the engine at lower RPMs. Finally with a heat sensor I found out that even though my gauge showed over 200 degrees no place on the engine was ever more than about 170-180. I am left to conclude that it is a gauge problem. It has been a source of frustration. My to do list includes a new gauge and sensor. I will replace the sensor first. Since I mostly sail the apparent overheating has not affected me much except when we are forced to motor for long distances. We had to motor 60 miles or so on Pickwick lake with the engine apparently running hot but no real problems. As long as the rpms were about 1700 even the gauge read normal. It was only over 2200 that overheating began. But again with the infraread sensor there was no real overheating.

 

[RichH]

jon; this engine doesn't have a metel impeller. the sen-dur unit doesn't either. at least mine doesn't. as a matter of fact both replacement impellers are the same.

QM engines DO have a metal impeller in the fresh water side, the raw water side has an "oberdorfer" type pump with a flexible rubber impeller.

 

[Cpt. Jon]

QM engines DO have a metal impeller in the fresh water side, the raw water side has an "oberdorfer" type pump with a flexible rubber impeller.

I think that if it's a QM engine with the Yanmar Heat X it has a metal one as indicated in my repair manual, but the after market Heat X setup on my boat did indeed have a rubber impelled that was the same size and type as the one on the raw water side.

 

[NotCook]

Antifreeze cooling efficiency

Check the condition of the antifreeze. Make sure it's green. I had a problem several years ago where I sprung a leak in the heat exchanger which caused sea water and antifreeze to mix in the block. It will cool but not as efficient as all antifreeze.

Just want to clear up a common misconception here: the specific heat of antifreeze is less than that of water. This means that for a given temperature change, the antifreeze will carry less heat each time it circulates from engine to radiator and back than water will. So, if the mix is too rich (more antifreeze), the cooling efficiency will be reduced because (1) the flow rate is less, and (2) less heat is transferred per cycle of the coolant.

The standard manufacturer's recommendation is to use a 50/50 mix of antifreeze and water. This represents a compromise between the cooling efficiency of water and the ability of the antifreeze to prevent the mix from freezing during cold weather. After all, the initial purpose of antifreeze is to prevent freezing of the coolant water. The water is the coolant, the antifreeze is not.

 

[Cpt. Jon]

True, but I am also under the impression that the antifreeze/coolant protects the enging from corrosion etc and thus the reason for using a 50/50 mix even in the hot months when there is no threat of freezing.

 

[MoonSailer]

Antifreeze also increases the boiling point and this protects the engine from local boiling causing local overheating. You can buy anticorroision additives for water.

 

[Ron20324]

And use distilled water for the other 50 percent.

 

[NotCook]

Good points about the anti corrosion additives and the distilled water.

 

[michaelanthony]

...sorry to side step but what is normal operating temp, and at what temp should alarm sound? Maine Sails guage shows 167. Is that the normal temp.
Thanks.

 

[Maine Sail]

Depends

...sorry to side step but what is normal operating temp, and at what temp should alarm sound? Maine Sails guage shows 167. Is that the normal temp.
Thanks.

It all depends upon your engine. My Westerbeke runs at 180, my old Universal engines had a 160 degree thermostat and raw water cooled engines can run as low as 140 degrees. The highest normal operating temp/t-stat I've seen on a marine diesel is about 180-185..