Overheating issue continues- merc 140 hp

[gpolkin]

To make a long story short- On a tight budget and trying to get a few more years out of a 1977 merc 140 with a rusted through head. Installed a used head, waterpump,t-stat, camshaft. After this is runs cool when hooked to a hose but hot idling at the dock. Installed a new lower unit waterpump hoping this was the issue, problem still there.

So I am betting I need to replace the exhaust manifold and elbow which I don't have the cash for unless someone can tell be where I can find one cheap. Before I do that I have one question. I noticed a slight bubbling above the manifold gaskest near the back of the engine. Could this gasket issue result in overheating if somehow the exhaust was crossing into water chambers in the mani? Wishful thinking?

Thanks for sharing your knowledge.

Greg

 

[hystat]

I noticed a slight bubbling above the manifold gaskest near the back of the engine. Could this gasket issue result in overheating if somehow the exhaust was crossing into water chambers in the mani? Wishful thinking?

probably wishful thinking, but... there were several different intake/exhaust porting sizes and patterns used on the various 2.5 and 3.0 heads.

I would triple check that the "new" head has the identical pattern and/or casting number. After that, sounds like manifold time (buy a riser gasket and do some checking inside) - but also verify the shutter in the exhaust hasn't fallen off blocking the downpipe.