Water temp regulators

J

jmeirhofer

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On my Cat 3126 motors my new Port motor is running perfect at 185. Which according to the service manual is right where it should be as the manual says 165-198F. And the overtemp alarm sounds and shuts down at 220F However.....

My Starboard motor had an issue last fall with the regulator sticking open. (I know, better than sticking closed). So I pulled out my parts manual and ordered the new regulator (7C-2190) from Cat and installed. The motor was running right at 200F last fall and while I did not give it much consideration at the time, I did think it might be a bit high. Well fast forward to this weekend and when I ran the boat Friday it warmed up to 205F and stayed there. Idle, WOT, did not make a difference. So I went back to do a little research on what I did.

According to the part number in my service manual and parts manual the thermostat for my motors is a 207F thermostat. So I am thinking that can not be right. I went to Boat Diesel and there seems to be conflicting info there as well in that they say the 207F regulator is correct. However there are a number of posts that people think temps of 205F are to high yet a few posters also have also said it is normal. Searching a few other websites including the CAT forum leads to the same thing.

I am just not comfortable with running it at that temp all the time. My thought is to either pull the thermostat on the port motor and get the part number off of it or just order the 180F thermostat from CAT.

So my question is, what temp do your CATs run at? And do you know what regulator you have?
 
John when I'm in town I often have coffee at the local coffee shop with a Giles and Ransome marine mechanic. I can tell him your situation and see if he can give me a CAT mechanic's professional opinion.
205 degrees seems high to me but I'm no mechanic and I don't pretend to be one either.
Bill
 
"According to the part number in my service manual and parts manual the thermostat for my motors is a 207F thermostat.""

That is your answer. As long as the rest of your cooling system is in good condition your engines should run at that temp. all day long with no problems. Higher operating temps are more efficient.
 
Thanks Bill. Getting other opinions is always helpful.

Capt Bill. I did make a couple of trips last fall with one being 2 hours and the temp held steady at that. I was out for an hour last week both at idle and on plane and the temp stayed right there. My issue is fear I guess. It would not take much to jump from 205 - 220. Sucking up a plastic bag for instance. I do understand the efficiencies of running at the higher temp. Especially where emissions are concerned.

The other thing is the operating manual saying that the normal operating temp is 165-198F. Seems I am missing a supplement to either the service manual or operating manual as they certainly do not match. I will see what Albin Cat has to say today and see what Bill finds out from his contacts. Either the port motor is running to cool or the starboard running to hot. It will be two weeks before I get back to the boat so I heave some time to research it.
 
It ain't broke, don't fix it. If it feels good to you change out the stat to a 180 degree. However: you have a closed system with the proper coolant and 207 is the current tecnology. You are getting better fuel economy at the higher temperature.

The boiling point of water with a 50/50 mix and a 15 PSI pressure cap is 265 degrees so your good to go. I would change out the other engine to a 207.
 
Thermostats are usually marked with their temp rating. Makers do change the specs and marine may be different than land specs. Personally I like to know that everything is OK and would recheck the stats ratings, different numbers would bug me. There are good reasons for choosing higher temp operation, better combustion, cleaner burning at low loads etc. That the temp does not change with load is good and indicates that the raw water side is probably flowing OK.
 
So I talked to the local CAT service department. He did confirm the regulator is the correct unit. It begins to open at 192 and is full open at 207. Normal operating temp for that serial number motor is 190-210. He suggested I pull the thermostat in the other motor and see what the part number is on it as that motors serial number should have the same thermostat. If it is the same number then it is sticking open as well. There is one that begins at 180 and is full open at 192. He also stated both motors should alarm at 215 and shut down at 220. So, I am going to get me a couple of gaskets and a couple gallons of antifreeze and see whats up I guess.

While I am not very comfortable with only a 5-10 degree window before an overheat condition causes an alarm, if that is the normal operating temp then I guess I should have to learn to live with it.
 
John, are these based on gauges or a pyrometer? I am sure you know the inaccuracies of temp gauges so a pyrometer taking measurements right on the engine at multiple locations is a must to evaluate thge operating temperature. I routinely compare readings from my pyrometer on both engines. None of my gauges, upper or lower helm agree with the pyrometer which is accurate. (Same thing is true with my digital tachs, but that is another story.)

Do the two engines really run at different temps and did you measure multiple locations on the block, heads etc.
 
Hi Rick. I have a handheld infrared temp gun. I did shoot both the oil pan and the regulator housing (the coolest spot) of the engine in question. They were within a couple of degrees of each other and the gauge. I did not think to do the same with the port motor ad I did not consider it to have a problem. I will do that the next time I am at the boat.
 
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