Mercruiser 165 1972 Sea Ray 190 Cooling Water Leak

[Ike]

Engine has a serious cooling water leak. This is a raw water cooled engine. There is a steady stream of water from underneath and behind the exhaust manifold, but I can't see exactly where it is coming from. (see photo with red arrow) And, there is trickle of water around a head bolt. Engine seems to run fine, but enough water coming out I have to run the bilge pump.

 

[lawndoctor]

I owned a 1971 SRV 190 with the 165, and I completely rebuilt the engine the first year I had it, so I'm very familiar with your setup. My first thought would be the manifold gasket. That manifold is a combination exhaust and intake manifold, and it is fairly easy to take off, just a few bolts. The gasket is relatively sparse in some place, meaning there is not all that much gasket surrounding some of the openings it must seal. In the photos it actually looks like one of the manifold bolts is new, so I'm guessing someone already took off the manifold at some point not too long ago. I would start there. My next thought would be the head gasket, but I would not go there first. Good luck, hopefully it's just the manifold gasket.

 

[Bt Doctur]

cracked block or manifold from improper winterizing or draining. There is no physical water connection between the engine block and manifold

 

[Ike]

I installed a new manifold in 2013. All the bolts were replaced. One bolt though, had to be replaced with a stud and a nut. That's probably what you are seeing. I was concerned about the gasket too. But I had a professional mechanic check it and do all the final tune up and tweaking and it was ok at the time. Another poster (on a different forum) said these are notorious for the head bolts rusting out because they penetrate the water passages. That may well be the source of the water around the head bolt. But, yes, the gasket was my first thought. But I won't know until I remove the manifold.

 

[lawndoctor]

That head bolt actually does look rusty compared to the adjacent one. No water in the oil?

 

[Ike]

No. No water in the oil. Just water flowing out around the head of the bolt. As far as I know this engine has never been opened up. The previous owner claimed that he had been told by the original owner that it had never been opened up, and he never did either. So 45 years isn't bad. Of course it sat for at least ten years before I bought it. But when I got it it still had good compression. But it did have a problem with water leaking from the riser gasket into the oil. That was about three years ago. A new gasket cured that.

Anyway, I don't have the time to deal with it for a while, but when I get it on to the trailer I can start taking it apart.

 

[Ike]

The above is a photo I took when I was replacing the manifold. The dark area is an exhaust port. But the head bolt in question runs through it.