Closed Cooling System - Engine Thermostat Concerns

tpenfield

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I just finished installed a closed cooling system - the FULL system type - on the port side engine. Mercruiser 7.4 LX MPI (see sig.)

So, I loaded it up with coolant, hooked up the muffs and gave it a few test runs for about 15 minutes total. Well, the first thing I noticed is that the engine ran a bit hotter than before it had the closed cooling system. It goes up to about 170-175 and fluctuates in that range. So, I assume that the thermostat is doing its thing (160 degree thermostat).

My concern is that the engine used to run in the 155-165 range. Since the closed cooling system is cooling the exhaust manifolds, there is a lot more heat going back to the engine and the heat exchanger.

I checked the original T-stat and that is a 160 degree, same as the new one with the new cooling system.

FWIW - this is the SJE #MC324 "Full" closed cooling system.

I am just concern about the higher operating temps with no load, and it will probably go higher with load . . . more in the 180-185 range. Plus, from a cold start, the exhaust manifolds get very hot before the t-stat kicks in . . . :rolleyes:

So, perhaps I should go with a 143 degree thermostat or just do without the thermostat all together. :confused:

What do you all think.??? :)
 

Don S

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Re: Closed Cooling System - Engine Thermostat Concerns

They will run hotter, you will probably see 180 under load. Perfectly normal with a 160? stat. However, it shouldn't exceed 180?
 

QC

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Re: Closed Cooling System - Engine Thermostat Concerns

So, perhaps I should go with a 143 degree thermostat or just do without the thermostat all together.
Just a general thermostat comment. They only control MINIMUM temp, so if the 160 is opening all the way, then a lower stat should not change max temp. This assumes your gauges are correct and that the 160 is fully open.
 

HT32BSX115

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Re: Closed Cooling System - Engine Thermostat Concerns

I have that exact same San Juan sys on my 454.

It runs "about" 160-180 degrees F or so. (never above) but I have not verified the gage and I have a 160 t-stat installed (actually I think the stat came with the kit)

I don't know what you mean by "very" hot. My manifolds don't "seem" any hotter than the block but again I haven't shot them with my IR gun.

You really shouldn't run without the t-stat.
 

tpenfield

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Re: Closed Cooling System - Engine Thermostat Concerns

Thanks for the replies . . .

I was able to get the second engine (starboard side) done this afternoon . . . I used the original 160 degree thermostat, as the one supplied in the kit looked too restrictive. I also drilled a couple of holes in the flange of the t-stat to give it some blow-by.

I was not able to fully test the different thermostat, because the sea water pump seems to have crapped out on the starboard engine. :facepalm:
 

QC

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Re: Closed Cooling System - Engine Thermostat Concerns

And you'd expect anything different? :p
 

HT32BSX115

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Re: Closed Cooling System - Engine Thermostat Concerns

Thanks for the replies . . .

I was able to get the second engine (starboard side) done this afternoon . . . I used the original 160 degree thermostat, as the one supplied in the kit looked too restrictive. I also drilled a couple of holes in the flange of the t-stat to give it some blow-by.

I was not able to fully test the different thermostat, because the sea water pump seems to have crapped out on the starboard engine. :facepalm:

Test your t-stat on the stove in a pan of hot water.

The one in the kit is not too "restrictive", It's just right.
 

tpenfield

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Re: Closed Cooling System - Engine Thermostat Concerns

Test your t-stat on the stove in a pan of hot water.

Yup, did that with the 'old' one and it was 160 dead nuts on. So, that went into the starboard engine . . . with the modifications

I have not done testing with the ones that came with the kits

The port engine still has the one that came with the kit (it is a funny looking thing, quite unusual).

Of course as boat luck would have it, I was not able to test the starboard CCS with the 'old' / modified thermostat, 'cuz the sea water pump STB and then hurricane Sandy struck :rolleyes:
 

tpenfield

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Re: Closed Cooling System - Engine Thermostat Concerns

Just ordered 2 new sea water pump impellers from iBoats.com

Got to support the web site you know . . . :)
 

Boomyal

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Re: Closed Cooling System - Engine Thermostat Concerns

FWIIW, I run a 180? stat in my San Juan closed cooled 5.0 roller cam motor. The exhaust manis are not included in my system. That motor runs dead on 180? from idle to WOT.
 

tpenfield

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Re: Closed Cooling System - Engine Thermostat Concerns

Yes, I am hoping that my slight modification to the 160 degree thermostats does the trick, giving the manifolds some water circulation prior to the t-stat kicking in.

i just need to do the same to the port side engine and get the sea water pumps squared away.
 

HT32BSX115

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Re: Closed Cooling System - Engine Thermostat Concerns

Ted,

I hope you inspected carefully for oil cooler blockage. When I did mine, I discovered that my oil cooler was completely blocked from previous impeller failures. I asked the previous owner if he had changed the pump/impeller and he said it was a recent change.


I almost believed him!

When I got it apart, I found the housing somewhat cooked, the impeller still intact but not looking very good and the oil cooler crammed with impeller fragments!

My oil cooler and PS coolers are separate. The PS cooler would probably pass large pieces. The oil cooler will not. I also removed the core plugs and flushed a LOT of rust, sand, and other debris from the block and exhaust manifolds before I installed the closed cooling system. It has worked flawlessly for about 6 years now.

Cheers,


Rick
 

tpenfield

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Re: Closed Cooling System - Engine Thermostat Concerns

Ted,

I hope you inspected carefully for oil cooler blockage. When I did mine, I discovered that my oil cooler was completely blocked from previous impeller failures. I asked the previous owner if he had changed the pump/impeller and he said it was a recent change.


I almost believed him!

When I got it apart, I found the housing somewhat cooked, the impeller still intact but not looking very good and the oil cooler crammed with impeller fragments!

My oil cooler and PS coolers are separate. The PS cooler would probably pass large pieces. The oil cooler will not. I also removed the core plugs and flushed a LOT of rust, sand, and other debris from the block and exhaust manifolds before I installed the closed cooling system. It has worked flawlessly for about 6 years now.

Cheers,


Rick

I sort of ran out of time this weekend, so that is on the list of things to check. Like you, I really do not have a good indication of how old the impellers are, etc. So, I plan to replace them just to start off fresh. I think that there are 2 coolers in line leading up to the engine, so probably the same setup as yours.

I also plan to put in sea water strainers, which I have found to extend the life of the impellers nicely, as the ocean debris, sea weed, sand, etc. does not get passed to the pump.
 

HT32BSX115

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Re: Closed Cooling System - Engine Thermostat Concerns

I also plan to put in sea water strainers, which I have found to extend the life of the impellers nicely, as the ocean debris, sea weed, sand, etc. does not get passed to the pump.

The Sea Strainer I have has holes in it sized to stop the large "stuff"............ It will not stop sand at all. You'll have to get a "sand trap" type strainer if you want it to block sand.

I am sure they work well but they're not cheap!


I think that there are 2 coolers in line leading up to the engine, so probably the same setup as yours.
I had to use needle-nose pliers to get the impeller fragments out of my oil cooler.....
 

tpenfield

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Re: Closed Cooling System - Engine Thermostat Concerns

The Sea Strainer I have has holes in it sized to stop the large "stuff"............ It will not stop sand at all. You'll have to get a "sand trap" type strainer if you want it to block sand.

I am sure they work well but they're not cheap!

....


I used the Sherwood #18029 sea water strainer on my last boat and bought 2 for this 'new' boat. They have a fairly fine mesh that seems to stop most things and a fairly deep trap, so sand does not find its way out of there. I think they were about $60 each.

The only thing that I don't like about them is that they are plastic and prone to cracking, which is not a good thing.
 

tpenfield

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Re: Closed Cooling System - Engine Thermostat Concerns

Just ordered 2 new sea water pump impellers from iBoats.com

Got to support the web site you know . . . :)

Got the new impellers from iBoats yesterday . . very quick delivery, so kudos to iBoats !!! :D
 

tpenfield

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Re: Closed Cooling System - Engine Thermostat Concerns

A quick update -

I took the SJE provided thermostat out of the port engine and replaced it with the original . . . But, before I put the original back in, I modified it, giving it a couple of by-pass holes in the flange. Of course I had to remove the heat exchanger and related hoses in order to get at the thermostat housing :rolleyes:

Before I put the modified thermostat in, I cooked it on the stove to make sure it was operating in spec.
IMG_1342AA.jpg


It started to open at 160 F and was fully open at 170 F . . . So, it is OK.

I put everything back together and test ran the port engine . . . much better.

Then I took a look at the starboard engine, as it was having sea water pump issues. It turns out that the impeller blades were completely gone as the internal 'rib' on the housing had broken off, leaving a nice sharp edge to cut and scramble the impeller blades :facepalm:.

So, it looks like I have to get an entire pump housing, not just the impeller.

I back-flushed the starboard cooling system to get the impeller fragments out of the system. then I hooked up the garden hose to the cooling intake and test ran the starboard engine. That one too seemed to be OK with its modified thermostat (less the sea water pump issue). I am now getting about 145 F, idling with no load on both engines, so I may have gotten away with a little less by-pass, but it should be fine under operating conditions. We shall we next Spring.

Here is a look at the finished product.

IMG_1338AA.jpg

I still have to deal with the sea water pump issue and I have a couple of sea water strainers to install as well.
 
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