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Volvo penta aq125a overheating

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Al3x2015

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I have a 1983 Volvo penta aq125a engine in my boat with a 270 outdrive. I am having an overheating issue with it and everything I have done doesn't seem to fix it. The head on my engine was rebuilt so it has a new head gasket and is showing no signs of a bad head gasket. I replaced the impeller, thermostat, heat exchanger, and the water pump is good. The engine is getting antifreeze flowing through it properly because I turned it over with the thermostat and goose neck off. When I'm in the lake at idle and take off the cap that covers the raw water strainer I am getting water rushing into it. But if I leave it off for more than a few seconds the water in the heat exchanger acts like it starts to boil and "boils" out of the heat exchanger. I put tape around an air chuck and put it into the copper tube that goes from the heat exchanger to the manifold and it was all clear. I blew into it after just to make sure and there was me restriction. Also if I am in the lake at idle my temp is just fine around 180 but at throttle it starts going up to around 220 after a minute or so. I have also checked the drain plug on the copper tube going from the heat exchanger to the exhaust manifold as well as the drain on the exhaust manifold itself and both drains have water going through them when the engine is at idle.
 
Sounds like you're losing raw water suction when on plane. That may be classic water neck fitting corrosion. That fitting is on top of the intermediate section of the out drive and the hose supplies raw water. At idle, the fitting is under water so any suction leaks aren't apparent. Get up on plane and the fitting is now sucking air so you don't have any raw water getting to the pump. In most cases, you won't be able to tell that it's eroded by looking at it while installed because the corrosion will be on the inside. Be sure to replace the beaded gasket when you replace the fitting.

It's called a thermostat housing on this page: http://http://www.marineengine.com/parts/sierra-marine/sierra-marine-parts-catalog-00844.htm
 
joe_merchant said:
Sounds like you're losing raw water suction when on plane. That may be classic water neck fitting corrosion. That fitting is on top of the intermediate section of the out drive and the hose supplies raw water. At idle, the fitting is under water so any suction leaks aren't apparent. Get up on plane and the fitting is now sucking air so you don't have any raw water getting to the pump. In most cases, you won't be able to tell that it's eroded by looking at it while installed because the corrosion will be on the inside. Be sure to replace the beaded gasket when you replace the fitting.

It's called a thermostat housing on this page: http://http://www.marineengine.com/parts/sierra-marine/sierra-marine-parts-catalog-00844.htm
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I actually was out looking at my water inlet hose from the outdrive to the stern. I already replaced the filler neck, hose and gasket but I noticed that the hose was completly disconnected where it went into the stern! I either did not tighten the hose clamp all the way or I have the hose the wrong direction. My hose does not have engine markings on it. Do you know which angle goes where?
 
I have fixed my cooling issue! It was intact the water inlet hose that was disconnected between the water neck and the transom. When at idle the inlet in the transom was below the water level allowing it to suck water in. Once moving the water is no longer where the inlet is on the stern so it was not allowing the water to be sucked up. I fixed the hose and drove the boat for about an hour with no issues at all!
 
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