Mercruiser 470 overheating

"This has probably been answer

"This has probably been answered already, but here goes. I bought this boat about a month ago not running. I'll try to be short with isues I've found since. After getting the motor to finally start I found the bellows ripped. Replaced bellows and gimble bearing. Then replaced starter. After all of this had a radiator hose blow due to over heating. Found the therostat was staying closed(replaced with 160 d ). Then overflow canistor was draining through overflow hose. Found closed system was empty. During this process temp never went over 150 d and overflow looked like boiling water and the overflow cap kept blowing off. The heat exchanger was cool on intake side and warm on exhaust side. The manifolds were extremely hot. So I pulled the thermostat out to see if that was the problem, but still overheated.Now my oil looks milky in crankcase and inside valve cover. Any help would greatly be apprecciated in helping me solve this issue. Could the head gasket have blown and caused all of this?"

The boat is a Sea Star 1979 wi

The boat is a Sea Star 1979 with a Mercruiser 470 by the way

also I noticed that at idle on

also I noticed that at idle one of the hoses between the heat exchanger and manifold was hard as a rock.....

"quite possible head gasket ha

"quite possible head gasket has given out, especially with the recent 'abuse'."

"I have 1978 Merc MCM 470 that

"I have 1978 Merc MCM 470 that we have just put in the water this year and the closed cooling system is losing coolant and starting to overheat but we cannot tell where it is going, not in the bilge. Engine is running fine and pulled 3 plugs and they are burning nicely. also no water in the oil. How can we test the 3" heat exchanger yes, still a 3" in there, to see if there is a crack in the unit and allowing the antifreeze to get out there. Compression test was good. There is also signs of steam coming out the back of the boat at the engine. Where else would the coolant be going? We appreciatre the help. as we are only on this Island (Pender Island, B.C.) for 2 more weeks."

James:

To add to what Makom

James:

To add to what Makomark said; check the exhaust manifold for cracks allowing water into the open exhaust valves. Use a hand pump and pressurize the cooling system to 16 PSI and see if it holds.

Risingsun:

Pressure test yo

Risingsun:

Pressure test your cooling system. Try to pinpoint the steam coming out of the engine.

well I found that the head gas

well I found that the head gasket was blown...During disassembly I saw that there wasn't an exhaust baffle in the exhaust tube...bracket is there but no shutter!!!