Aq125a overheating

[Al3x2015]

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.

 

[dennis461]

you should have a copper tube on starboard side, under the exhaust manifold.
It should have a drain on it.
Open it up and see if water flows out .

 

[Al3x2015]

you should have a copper tube on starboard side, under the exhaust manifold.
It should have a drain on it.
Open it up and see if water flows out .

I have done this in the lake at idle as well as the drain in the manifold itself and water flows out of both of them.

 

[Fishermark]

The water neck on the outdrive where the hose connects sometimes corrodes and causes an air leak. Take a look at the condition of the water neck and surrounding area.

 

[Al3x2015]

The water neck on the outdrive where the hose connects sometimes corrodes and causes an air leak. Take a look at the condition of the water neck and surrounding area.

I already replaced that as well as the gasket for it and the hose that goes between the water neck and the transom. I did notice today that where the hose connects to the transom though it was disconnected there so I am on my way to the lake now after tightening it down to see if this was my issue or if I have another issue at hand as well.

 

[dennis461]

I have done this in the lake at idle as well as the drain in the manifold itself and water flows out of both of them.

OK, and with the gushing you described, the plumbing seems to be working properly.
If you idle at the dock for 20-30 minutes, or troll around at 5mph. Will it overheat?

 

[Al3x2015]

I have fixed my cooling issue! It was the water inlet hose 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!

 

[Fishermark]

Glad you found it!