Water leak from exhaust cover housing

[Chief34]

Hello, I have a boat that I recently fully restored... It has a 77 Merc 115 inline. Serial # 4568971 . I have been running it and it starts and runs great so far. I I've been working out the little kinks that have popped up and now I have another...I noticed before that there was a "scrape" on the exhaust cover where the control cable slide is.

Now, that spot has developed a hole and or a crack in that scrape mark and water is coming out of there. I assumed it was no big deal because I know water is injected through the exhaust, but I got to thinking about it and I don't know when or where that happens... Is it normal for water to be in/under the exhaust housing cover?

Any help is greatly appreciated. This site has been a great resource during this process!

 

[Chief34]

Here is the photo... It's about an 1/8" hole in the exhaust cover. Water squirts right out of it while running. Does anyone know if it's normal for water to circulate through there under the exhaust cover? Everything seems to be working and running fine.

I was going to take the cover off , clean it up and weld the hole shut but I'm seriously debating just putting some jb weld or maybe two part putty on there and sealing it that way. I put my finger over the hole and it didn't have any pressure that I could feel really...

 

[schematic]

Anytime you see a water leak on a engine of that vintage, there is a good chance the gasket is rotten and letting go. Pull the covers and check the condition of the gaskets to be safe.

 

[Chief34]

It's probably hard to tell in that pic but there is about an 1/8" hole in the aluminum cover where it's coming out. I don't see anything leaking out around the cover gasket. What I want sure was if the water is supposed to be going under the cover to begin with... I was looking at my manual at it seemed to indicate the water flow routing went from the water pump up and behind that cover, then into the head ports and so on... So if that is the case, I should be good..

 

[tommarvin]

I believe you have a 1/8" hole, Good for you to not pull the exhaust cover off first,
Not sure if JB weld is best on aluminum worth a search, clean it well,clean it with alcohol before you plug the hole with something, polyester resin, bondo, gorilla glue, forget that two part epoxy is what you need to plug the hole.
Better search and find your exhaust gasket in case plug the hole doesn't work.

 

[flyingscott]

Take the cover off and inspect the gasket. Water and exhaust should not mix at the point. If they do there is an excellent chance of it getting to the cylinders themselves. That will be a costly lesson learned. Holes need to be fixed properly.

 

[schematic]

Amen!

 

[Chris1956]

If the leak is not from the gasket, like it sounds, it can be repaired with a dab of silicone caulk. You risk breaking many bolts, when removing the exhaust cover. I wouldn't recommend removing the exhaust cover until you absolutely have to.

If the action of the shift slider made the hole, you need to fix that. If the cover simply rotted thru in that spot, chances are it will rot out in another spot, real soon.

 

[Chief34]

Yes, it seems as if maybe the PO had the shift cable removed and the back edge of the slide linkage poked and rubbed it right there and after I got it running it ended up creating that hole right there... I scuffed it up with sand paper and used the two part epoxy putty to fill the hole... I Let it dry and so far it seems good to go. It's not leaking anymore.

As far as the other couple of comments about the water not supposed to be in there at that point... Am I missing something? In my manual the"flow" schematic shoes the water coming up from the water pump through the water time and into the exhaust cover then into the head ports... Is that not correct? Should water not be under that outer exhaust cover?

 

[racerone]

Water circulates behind that cover.-----Has to keep that cover cool.

 

[Chris1956]

That cover should be the temp of the water in the lake/bay/ocean, at idle, warmer at cruise speed.

To be clear, water flows up from the waterpump, thru the inner water jacket around the exhaust ports, and spills over into the top of the cylinder head and exhaust covers, before running into the water outlet in the midsection and mixing with the exhaust.

 

[Chief34]

Ok, thanks a lot guys... That's what I figured. So far the little plug job worked great.