5.7 issues overheating

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rooferdave
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5.7 issues overheating

Post by rooferdave »

going to do this in two threads, I have been on this for quite a while, any help would be cool and also the title should come up for an easy search for others. Figured I have pretty much got every thing covered in one place for overheating issues (except what is causing mine :cry: )

1988 mercruiser with electronic ignition, it is raw water cooled, (not a closed system) runs hot at 185 on gauges but 155 on ir gun, (boat is a 1976, repowered partially by po, finished by me)
the other engine runs 170 on gauges and 125 on ir gun.
when I load up the engine temp on the problem engine (port) quickly goes up to 200plus, upon throttling back it recovers to 185 and 155 on ir gun.
-impeller changed
-compression 215psi +/- 4 degrees across the board
-engine backflushed
-custom 4" exhaust installed
ran clear lines on engine saw some bubbles off one bank, removed head in question, magnafluxed, cleaned up and replaced on engine
-belts fine
-themostat replaced
-no leaks on engine
-checked timing, is to specs (retarded could cause overheating)
-water flow seems good out exhaust

The only thing I have not changed is the waterpump on the engine (not impeller) but it is not leaking and water flow does appear good out exhaust, can't see this being the prob

Also pehaps the engine is running too rich, this may cause heat issues so I am going to swap carbs to see.

have I missed anything????? My liver can not take much more thinking about this!
Last edited by rooferdave on Thu Jun 28, 2012 2:12 pm, edited 1 time in total.
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koviak
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Post by koviak »

Don't forget the trans oil
cooler. Does not take much to restrict the flow.
Dennis
1989 10 Meter Mid-Cabin
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rooferdave
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Post by rooferdave »

koviak wrote:Don't forget the trans oil
cooler. Does not take much to restrict the flow.
sorry, forgot to list that, it was taken off and checked with the back flushing operation, nice call! thanks for reminding me.
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BarryL
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Post by BarryL »

Is this a "Closed Cooling" system with heat exchanger or raw water cooled. if it is a closed system you might want to try flushing the system with Phosphoric acid and then flush with a mild baking soda solution to neutralize the phosphoric acid. I flushed my brothers closed cooling system on Lake Mead after he spent thousands for marina to diagnose with no success. Since the flush she runs cool as a cucumber.

If it's raw water or closed have you replaced the thermostat? it might be hanging up. Usually a low flow problem will run ok at throttle but you will notice a lot of heat soak when backing down (temperature spike) and the available cooling water flow is reduced.

It's a head scratcher.

Let us know what you find.

Barry
I love my boat! It takes all of my money and doesn't bitch.
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rooferdave
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Post by rooferdave »

thanks Barry evertime I reply to your post I get a forbidden error!

I give up 4 times now !!!
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rossjo
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Re: 5.7 issues overheating

Post by rossjo »

rooferdave wrote: ... runs hot at 185 on gauges but 155 on ir gun ...
... the other engine runs 170 on gauges and 125 on ir gun ...
... when I load up the engine temp on the problem engine (port) quickly goes up to 200plus ...
... upon throttling back it recovers to 185 and 155 on ir gun ...
What temp is the IR gun when your inaccurate gauges read 200+?

At lower temps, your gauges are off by 35degrees, and 30 at higher temps, so
200+ sound like about 170-180 on the IR gun ... seems like your gauges are just wrong. Do you have a lot of steam coming out the exhaust?
Captain Ross, 2009 Trojan Boater of the Year
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"Mack Attack" Chaparral 244 Fish, SeaPro 180, McKee 14, Montauk-17
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rooferdave
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Re: 5.7 issues overheating

Post by rooferdave »

rossjo wrote:
rooferdave wrote: ... runs hot at 185 on gauges but 155 on ir gun ...
... the other engine runs 170 on gauges and 125 on ir gun ...
... when I load up the engine temp on the problem engine (port) quickly goes up to 200plus ...
... upon throttling back it recovers to 185 and 155 on ir gun ...
What temp is the IR gun when your inaccurate gauges read 200+?

At lower temps, your gauges are off by 35degrees, and 30 at higher temps, so
200+ sound like about 170-180 on the IR gun ... seems like your gauges are just wrong. Do you have a lot of steam coming out the exhaust?
sorry my mistake, when the hot engine is at 200+ the ir reads 155

at the 180-185 range ir reads 125-29



we did not see steam out the exhaust but when docking some one commented that it seemed to be steaming a bit, but us onboard did not notice

gauges are certainly wrong, but is 155 not dangerously hot for a mercruiser? Also the 30 degree spike is uncool (snigger :lol: ) under load
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rossjo
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Post by rossjo »

155 should be OK for a Mercruiser (Crusader?).

I believe you should have a 160deg thermostat (if its MPI). Carb'd is probably 140deg F though ... so maybe she is a little hot since its a 1988 and probably carb'd.

Some MPIs are even 170deg F, but that too high IMO.

Where are you aiming for your IR reading?
Captain Ross, 2009 Trojan Boater of the Year
"Viva Mahia" F32 Cummins 6BTA diesels,
"Mack Attack" Chaparral 244 Fish, SeaPro 180, McKee 14, Montauk-17
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rooferdave
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Post by rooferdave »

the engine is carb'd and the thermostat is a 143 deg

I had a mechanic come down last week and run the ir gun this time as the admiral is getting impatient and I figure two of us can get this done quicker, he took a few readings to be sure. I can ask him where he took the readings, I was busy driving this time
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rossjo
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Post by rossjo »

Worst case, the water passages in the raw water cooled 1988 engines could be corroded, but that's probably not it.

How old are you exhaust manifolds and risers? Are they restricting flow?

What is the age/condition of your engine mounted pump (not the seawater pump)?
Captain Ross, 2009 Trojan Boater of the Year
"Viva Mahia" F32 Cummins 6BTA diesels,
"Mack Attack" Chaparral 244 Fish, SeaPro 180, McKee 14, Montauk-17
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Paul
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Post by Paul »

One thing to keep in mind is that readings taken from the outside of the engine castings with an IR will always read a bit lower than the actual internal coolant temperatures. This is due to the outside of the castings being cooled by the air that surrounds them.
Paul
"Cruise Control" 1978 F-26HT
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Lumpy
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Post by Lumpy »

I have 86' 454/350 Crusaders. The starboard would idle at 150ish but under power would creep up and up to over 200. This is what I found;
The strainer has a in and out flow, it was in backwards, the out-flow had the wrong size hose, 1-3/8, should have been 1-1/4. Fixed that and the problem was still there. Next I took the flange off the sea-cock and a calcium build up had the blocked all by a 1/2 in. Took my screw driver and removed the build-up. She now run at 180 under power where it should be. You may also want to rebuild the raw water pump. Changing the impeller is the easiest but having the seals replaced could make a difference.
Good Luck,
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rooferdave
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Post by rooferdave »

thanks for the suggestions, when the raw water pump was changed, the dealer sold me an entire new housing, said it was a wise decision so I did.
When I backflushed the system it seemed pretty free, also when I was assembling the engines I cleaned out the manifolds.
I will let you all know how things go this weekend
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