8.1 horizon overheated

F

Festivals

New Member
Mar 29, 2013
13
Long Island ny
Boat Info
2008 sea ray 330 sundancer
Engines
Twin 8.1 horizons inboards
I recently had my boat serviced because starboard motore was running 12 degrees warmer than my port for two years. We changed exhaust manifolds and pumps to be sure. Both motors seem to be cooler for about an hour then starboard started running hot. Changed heat exchanger on starboard motor and it ran cool for about 10 hours. Then Heat problem was back. Removed heat exchanger to so it clogged with pick junk. Put on new heat exchanger again drained motor as good as possible. Now it’s running cool again. Anyone have an idea on best way to flush system? And flushing cleaners that will work? I included a picture of junk by thermostat
 

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Looks like the sludge that occurs from mixing red and green coolant. I'd drain it, fill with water and flush that out after a couple hours. Then repeat
 
Looks like standard antifreeze was mixed with a newer OAT antifreeze. That would produce that type of sludge. That stuff is all in your system and needs to be cleaned out. I'd start by pulling as many hoses off and flushing with fresh water to get as much out as possible. I do a radiator flush (as many time as it takes to get no debris in the coolant), and then refill with the recommended coolant.

I'd check the other side while I'm at it.
 
scoflaw said:
Looks like the sludge that occurs from mixing red and green coolant. I'd drain it, fill with water and flush that out after a couple hours. Then repeat
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That is what I did, I was wondering if there was a chemical flush that I could use.
 
dtfeld said:
Looks like standard antifreeze was mixed with a newer OAT antifreeze. That would produce that type of sludge. That stuff is all in your system and needs to be cleaned out. I'd start by pulling as many hoses off and flushing with fresh water to get as much out as possible. I do a radiator flush (as many time as it takes to get no debris in the coolant), and then refill with the recommended coolant.

I'd check the other side while I'm at it.
Click to expand...
That is exactly what I am going to do. Thank you
 
I think it’s 212 degrees. I am not sure. My 2008 8.2 Engines usually runs below 170. My recent issue had it up to 180 but that is high for my motor. No alarm goes off at 180. Hope this helps
 
I see that Preston has a coolant flush that is designed to clean out coolant systems. Has anyone ever used it? It claims that it totally safe for metal, gaskets and hoses.
 
Festivals said:
I think it’s 212 degrees. I am not sure. My 2008 8.2 Engines usually runs below 170. My recent issue had it up to 180 but that is high for my motor. No alarm goes off at 180. Hope this helps
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My starboard engine temp went to over 200 and oil pressure went over 60 with no alarm. I drove at 23 mph for about 30 min back to the dock prepared to stop if alarm went off. At the dock I hooked up my scanner and everything reAd fine. I’m figuring something spiked the gauges and they stuck there
 
I would take the heat exchanger out of the circuit and flush with a hose through one of the heat exchanger hoses and see how that works first.
I guess any kind of radiator flush would be fine.
I would check the other motor too for same thing.
If green antifreeze was in this one its probably was put in other motor too.
 
You'll probably laugh, but something like that needs a low suds surfactant clean followed up with a low strangth acid followed by a neutralizer and a rinse.

I've seen folks suggest cascade rinse, then a vinegar rinse, then a baking soda rinse, then a water rinse. Do not let the acid sit in there too long.
 
Thank you all for your replies. I have flushed both motors and going to try this a few more times to be sure its all clean. Just wanted to share and help.
 
Get a heat gun and compare similar engine parts when the motors are running.
 
I did that at the start. it didn't help me much. the exhaust was cool and rest of the motors parts are inside normal range. in the 170-178 range. my problem was clogging the heat exchange. I did not wait for total blockage so heat was up from 168. I knew my boat well so I noticed when one was running in high 170's. problem is gone for now cleaned both heat chargers and flushed both motors even though only one had an issue.
 
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