1969 Mercury 1250 overheated, now leaking water from spark plug holes

[Jammer864]

Engine overheated and teardown found a piece of melted plastic at the top of the water tube where it enters the powerhead. Removed the plastic obstruction, reassembled, and test ran. Now I have water flow thru engine and it runs fine but water is leaking from several spark plug holes. Compression is 130's in all cylinders. Hoping its the Cylinder Block Cover Gasket pn 27-47226 and not a cracked block. That gasket is NLA-Obsolete and a search of several old merc and used parts websites turns up nothing. Anyone else run into this problem and found a solution? The engine is in very good condition mechanically and cosmetically and if I cant find a gasket, I have no chance of salvaging this one.

 

[sutor623]

Man that sucks. Definitely warped the head or melted that head gasket. I bet if you contact Bill from Maxrules he will help you as best as he can. He has helped me find parts for my '67 650 that I couldn't find anywhere else. There is also a list of salvage yards on this site, although I am not sure a used headgasket will do you any good.

 

[racerone]

There is no cylinder head on this motor !!!!-----Simply replace the water jacket gasket to stop the water leak.--Nothing complicated at all.

 

[Chris1956]

Dry off the cylinder head water jacket and smear some silicone caulk over the area of the leaks. Let her dry and that should stop the leaking. You may need to repeat after each changing of the spark plugs.

 

[racerone]

???----Make a new gasket !!!---Replaced that same gasket on a 66 model 65 hp a couple of years ago.--Listed as obsolete , but I had 6 of them hanging in the shop.

 

[Chinewalker]

I'm with racer one on this - make a new gasket!! Remover the cover, use it as a template and cut a new gasket. Nothing fancy to it... Will also give you the opportunity to inspect the water passages for debris, etc.

 

[Jammer864]

Good suggestion to just make another gasket. I wasn't sure if it was a composite type or not....doesn't sound like it. I will get to looking for a large piece of gasket material. Thank you for all the responses. Will let you know how it goes.

 

[Chris1956]

One of the risks or removing the water jacket cover is breaking the 1/4" bolts that hold it on. On some of the motors, they are thru bolted or can be thru bolted when replacing the broken bolts. I recommend heat, penetrating oil and prayer., when removing the bolts.

Best of luck

 

[Faztbullet]

Cylinder Block Cover Gasket pn 27-47226

How many you need as buddy has 2 NOS in stock and want $15 ea???

 

[hotrod53]

My '77 merc 500 leaks around plug #1, has been just dripping for a couple of years. I'm scared to death to try and remove the bolts for fear that they will break. Couple that with the fact that some bolts are down inside the cowl where you can't reach. I may even try and seal it externally with RTV, it's that small.