Water Leak

[sealyons]

My '85 Mercruiser MR 200 has a water leak on the port side. It appears to be coming from a plug on the cylinder head between ehaust ports 1 & 3. It looks like an allen wrench will fit it. What is this plug for and can I attempt to tighen or replace it?

 

[Don S]

Re: Water Leak

It is a cast iron plug to fill a hole used during the manufacture of the head. Yes you can replace it, forget about tightening, that's not the problem.
The fact that it's leaking probably means it has corroded through and the rest of the engine isn't far behind. There is a similar plug on the back of the head on the other side of the engine.
I would bet on electrical corrosion as compared to just rust. Unless you have a raw water cooled engine in salt or brackish water.

 

[Bt Doctur]

Re: Water Leak

just did one by drilling and tapping what was left of the plug with 1/4 in. pipe tap and installing a allen head plug from a fuel sep.not the hex head type.

 

[sealyons]

Re: Water Leak

Is there a tool I can use to remove? An allen wrench, 1/4, 3/8, & 1/2 inch drive socket wrench will not fit. It is a square opening. I would rather try to get the plug out first before I start drilling & tapping.

 

[sealyons]

Re: Water Leak

I seem to be having difficulty finding a tool to remove the plug. Can I just grind down a 3/8ths extension to fit the square opening?

 

[Haut Medoc]

Re: Water Leak

Yes....
Are you sure it's not metric?
Have you measured the actual opening?
I would be very surprised if it were not a standard size....JK

 

[sealyons]

Re: Water Leak

I have not actually measured the opening, however a 5/16th allens wrench fits nicely on two sides...just not enough on the other 2. I am just surprised that I can't find the tool to do it with. They had to get it on there somehow!

 

[Bt Doctur]

Re: Water Leak

You want to remove a cast iron plug from a cast iron block that has most likely been run in salt water since 1985.If you figure it out PLEASE let me know how.
Always resorted to the drilling and tapping method,1/8,1/4,3/8,1/2 .drill the offending part completely out and retap to oem or the next oversize.

 

[sealyons]

Re: Water Leak

The heads have only been on the boat for 7 years, two of which were on land. I'd rather try to get it out first before I drill & re-tap. If it wont budge than I'll drill. I just filed down a 3/8" socket extension to 6/16ths.....we'll see what happens in the AM.

 

[lilmandavis]

Re: Water Leak

heat but not too much be gentle. cast like to crumble. id check to make sure you shore power isnt leaking into your metals.