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1987 25HP Merc Water Leaking through a hole in engine block

R

rmcderm313

Regular Contributor
Hi All,

When my 1987 25HP Merc is running, water is coming out of the hole identified in the picture below. It is flooding the cowl a bit. It certainly doesn't look like it should have water coming out of it and not be routed somewhere. Can anyone tell me what is going on? My motor is also "coughing" (see my other post) and I wonder if it is related to water being somewhere it shouldn't be.

I did just replace the gasket between the engine block and the adapter plate assembly because I thought that was where the water was coming from, but it's coming from this hole.

Thanks,
Rob



HoleLeakingWater.jpg
 
If I am looking at this diagram correctly, that part #2 is identified as a "Cowel Pin, Cylinder Block". Is it possible that there is just a cowel pin missing. I can't imagine why there would be a pin there. Very strange..

block.jpg
 
I'm trying to figure out whether the hole on the diagram (where that dowel #2 is shown), is the hole where the water is coming out in the video. It's hard to tell from the diagram if this hole is covered by the crankcase.
 
I'm with Jeff on this one - totally stumped (and been pondering this for a few days now) - can't even figure out what should/would/might be there or how the water is getting up to that hole.

I would tap it (the hole) and put in a stainless bolt with a bit of gasket seal (high heat) slathered around it and call it good - don't think you would find that in the service manual, but would at least stop the leak...
 
When I was removing the lower crankshaft wear sleeve, I noticed the issue with the water leaking through this hole. There is a hole that goes straight through the bottom plate of the engine block from the back of this hole through to where the water comes in. You can see the light from the flashlight shining through in these pictures.

photo 2 (18).jpg
photo 1 (17).jpg


So mystery solved. I could tap the hole and screw in a bolt as Graham suggested, but where I found the source of the water is there another way to plug this side with some sealant or something?

Thanks,
Rob
 
There was probably some kind of plug in there to start with - might have been rubber or a welsh style just pressed in.

The water pressure is not "severe", probably somewhat less than 15 psi so you could probably use some silicone sealant, marine "goop" or any similar product.

Still can't figure the purpose of the hole in the first place..
 
kimcrwbr1, I think you are probably correct, as it doesn't look like water should be getting to the "compartment" where the hole is. Although I did just replace the base gasket and the problem was still present. However I did not use any sealant on the gasket when I first assembled it. I plan on using silicone when I re-assemble this time, maybe that will keep the water out of that compartment to begin with and solve the problem that way.

Jeff, yes I think you are right as well. From the parts diagram I included above it shows a dowel pin in what I think is this hole. The only thing I can speculate is that there is another model of crankcase that is used with this engine block, and that model is wider and covers that hole and hence needs that dowel pin to line up. When mated with this crankcase, you are just supposed to plug it with a dowel pin as the diagram shows. That is definitely missing from my engine.

Between using silicone on the base gasket and some silicone sealant in that hole, I'm hoping the leak will stop. If not, I'm going back to Graham's original suggestion and I'll tap and fill it with a bolt/sealant.

Thanks guys,
Rob
 
I used some silicon sealant and it seems to have stopped the leak for now. If it returns I'll tap the hole and plug it with a bolt....
 
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