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Mercruiser 470

dennis_b

New member
Ok I flushed the cooling syste

Ok I flushed the cooling system(jiffy lube) and switched to my good heat exchanger. Then replaced the t stat and radiator cap. I am out on the water and it is again bubbling in the recovery bottle and blowing water out the overflow line. Once the water level goes down it starts to heat up. Any suggestions on where to go from here?
 
"Cracked manifold or head gask

"Cracked manifold or head gasket since probably exhaust bubbles are in the overflow tank. Compression test w/tell you if it's a head gasket. Pressure test cooling system w/tell you if it's the manifold or block. Antifreeze in the oil is a cracked block or blown circulating pump seal. Antifreeze in the spark plugs is a cracked head, head gasket or exh. manifold."
 
Clogged incomming water supply

Clogged incomming water supply port? no heat exchanger cooling?

Jet drives "syphen" water thru the impeller (jet prop) housing dont they?
 
"I had the same problem. The c

"I had the same problem. The cure was a new head gasket. If you are lucky you didn't crack anything. While you are in there check the bore walls for ridges and other damage. Make sure to use the correct gasket sealer, aluminum block/cast iron head.

Good Luck"
 
"Update:

Compression test &


"Update:

Compression test (cold engine - boat in driveway) 140# in 1st and 3rd - 150# in 2nd and 4th. Pressure test 14 psi held steady for 30 minutes plus until I released the pressure.

I installed a clear 3/4" hose between the raw water intake and the voltage regulator - plenty of water flow at all rpm's.

The water in the recovery tank turned an orange color and smelled a bit like exhaust. Is this a bad head gasket? Still overheating at 3000 rpm's and above. Runs really cool if 2500 or so or under. Also the oil pressure is really high at all rpm's.

Any help would be greatly appreciated.

Thanks,"
 
Do another compression test on

Do another compression test on a warm engine. The aluminum block expansion may cause a cracked head gasket to move enough to rear its ugly head.

Are you using water in the closed cooling part of the system?
 
I had the same symtoms on my 4

I had the same symtoms on my 470. I tried everything else then changed the head gasket. My compresson was good also. Only after opening it up did I find the blown gasket. It wasn't obvious you had to look for it. It was enough to push the water out of the overflow and overhead the engine.
 
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