1986 Merc. OB 115hp inline 6 water leaking

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chrisatthelake

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Jul 7, 2011
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There is a small port next to the top spark plug with water leaking out of it. Looks like something should be in that hole. Engine starts and idles fine. Even revs fine when in neutral. Under load it looses power. Not sure if the water running down all the plugs is causing that.... Please reply with usable info; it would be greatly appreciated.
 
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Chris1956

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Mar 25, 2004
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27,158
Re: 1986 Merc. OB 115hp inline 6 water leaking

Does that motor also have a plastic elbow screwed into the cylinder head water jacket with a rubber tube on it? If so, the hole you refer to is extra, for a water pressure gauge perhaps. If not, the hole is for the elbow and tube of the telltale indicator. I presume it is a tapped hole?
 
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chrisatthelake

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Jul 7, 2011
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Re: 1986 Merc. OB 115hp inline 6 water leaking

Chris1956 said:
Does that motor also have a plastic elbow screwed into the cylinder head water jacket with a rubber tube on it? If so, the hole you refer to is extra, for a water pressure gauge perhaps. If not, the hole is for the elbow and tube of the telltale indicator. I presume it is a tapped hole?
Click to expand...

Yes there is a brass fitting with a rubber tube about 2 cylinders down. The hole in question looks to be about a #10 hole with maybe a 32 thread in it. I wonder if I can just plug it with a bolt and removable lock-tite. Think it could cause any damage to the water jacket, pump, or head?
 
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Chris1956

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Mar 25, 2004
Messages
27,158
Re: 1986 Merc. OB 115hp inline 6 water leaking

You may plug it or better yet install a water pressure gauge. The hole should be 1/4" pipe thread. A 1/4" brass plug will seal it.
 
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