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Coolant overflow from radiator cap

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jitty23

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"hello im a newbie here and ha

"hello im a newbie here and had just bought my first boat, its a 1981 180 cuddy, it has a mercruiser 470 in it. well the first problems i encountered was the coolant leak from the water pump cover area so i had a marine tech replace just the seals, i then had the carb rebuilt and engine tuned up with new plugs wires and new cap and rotor and new thermostat. engine starts right up and has no electrical issues or starting issues. 1 thing i noticed was the coolant overflowing from the radiator cap area, i replaced the cap but it still continues to overflow. the motor does not overheat so far. what are some things i should look into as far the cooling system, i know i should replace the water impeller in the out drive as far as a maintanence requirements. what are some things to consider, also iu broke a small thin tubing that connects to the trim area in the back of the boat, i ordered a new hose which was only 22 bucks. the fluid leaked out and im not sure how to fill her back up and what to fill her up with. the hose coonects to a box looking object which i know its for the trim because when i raised the trim fluid was leaking out of the broken hose. the hose's diameter is actually smaller than a straw kinda the size of a vaccum hose but its a hard white plastic."
 
"Use merc. power trim fluid fo

"Use merc. power trim fluid for the hose. Run the OD up and down a few times and it will take care of bleeding out any air. Recheck the fluid level in the PT reservior.

The cooling system works like an auto but uses water to cool the heat exchanger instead of air. The impeller pumps raw water to the exchanger which draws the heat out of the cooling tubes that are filled with anti-freeze. As the engine heats up and pressurizes the cooling system, expanded anti-freeze is forced out thru the cap and into the overflow tank. It should stop after a few cups of it flows into the tank. If it keeps flowing into the O/F tank while the engine is running, there may be a overheat condition from a blocked exchanger or if not overheating there could be a blown head gasket allowing combustion gases into the cooling jacket which would increase the system's pressure thereby forcing more coolant out of the system. Checking the coolant for exhaust gases will rule out a blown head gasket from the cooling jacket to combustion chamber."
 
"hay guy, how do i check the c

"hay guy, how do i check the coolant for exhaust gases, can you give me some instructions on how to perform that test. i greatly appreciate your advice and as well as your quick response. ohh and i was referring to the cap on the motor like the radiator cap not the overflow bottle"
 
You need a mechanic friend w/a

You need a mechanic friend w/an exhaust analyzer probe or install a clear water hose from the engine to the exchanger and look for numerous bubbles. Some auto parts store may have one to probe the main tank for gases.

A compression test on a warm engine will pinpoint a low cylinder. Hand turn the engine until both valves are closed (dist. rotor will point to the plug wire when there) and inject compressed air w/an adapter into the spark plug hole. Watch the tank for bubbles.
 
"Guy has this one cornered but

"Guy has this one cornered but... the minute i read this i thought "head gasket". Plain and simple, if you keep pushing coolant out of the pressure cap (past a quart or so) - you've got a head gasket issue or a cracked head. I've seen it a lot on cars that have been overheated. I can't think of another reason you would see that symptom."
 
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