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M/C 470 Still Getting Hot?

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a1nowell

Contributing Member
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Today, 04:24 PM
a1nowell
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Seaman
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M/C 470 Still Heating Up!
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Two weeks ago my M/C 470 heated up while out fishing. Here is what I found and steps taken to cure the problem:

1)Took the outdrive off and found the plastic tube melted. The impeller was in tack, not damaged.
2)I got a w/p rebuild kit, rebuilt the pump, new impeller, new gaskets, new plastic pipe.
3)Removed old voltage regulater and have direct hose connection from transome seawater pipe to heatexchanger.
4)Flushed seawater pipe from the gimble housing thru the transome and back again.
5) Flushed the seawater side of the heat exchanger and both ways ,in and out all flowed good
6 Flushed the engine water side of the heat exchanger both inbound and out.
7) Replaced the thermostate (also tested it before installation).

Tested the engine in the drive in a 55 gallon rain barrel with water above both sterndrive finns.
Tested it with the muffs on.

The temperature rises very slowly probably 10 to 12 minutes until it gets to about 160. Then it continues to rise but slowly, at about 1200 RPM. I turned it off before the temp reach 200.

Any suggestions?
 
remove the exhaust elbow . if it is all rusted up inside replace.

the thermostat must be the MC470 one. this is a 2 stage thermostat. this directs coolant into the heat exchanger when temp rises.

check the timing at 750 rpm 6-8 deg. very hard to get exactly on the mark.

make sure the water pump is not leaking coolant. 14psi coolant cap no higher .

if this checks out do coolant pressure test for gasket failure
 
I had same problem, exhaust manifold was clogged, I'm new to this forum but if you have a 3" heat exchanger upgrade to a 4".
 
Maybe heat exchanger needs to be acid washed. Maybe exaust water shutter melted and dropped into the lower part of outside gimbal blocking exaust flow. Happens alot. Have you ever removed riser? Could be all choked off with rust. Has your oil level increased? Do you have water in oil? Is your water circulator pump intact? Did you install the proper thermostat? (165 degree) Do you have any coolant dripping from underneath timing cover from weep hole? Need more info. to help you. I have the same engine on my boat. all the best, Tom
 
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