Water coming from around spark plug - 77 merc 40hp

[BoxMN]

Hi all,

Helped bro in law pump in a impellor in his (just bought) '77 Merc 40 hp. It is a 2 cylinder. When he bought it the water pump was not working at all, but motor was running. The impellor was totally shot, fins torn off, not pumping water at all.

Got the new impellor in, it pumps great, strong stream. We had it in tub and was looking at it, and noticed that there is water coming from what looks like just below, but in the same "hole", as where the top spark plug is threaded. The top cylinder is firing, so we are thinking that there is just a crack in the "cooling plate" (whatever that might be called) and water from inside the cooling mechanism is squirting out.

Does this sound like what it might be? Can you just get a replacement plate to fix that? Could it be anything else?

We are thinking that the previous owner was running it without the water pump working, and it might have gotten too hot and something cracked, but it seems like everything is running ok, just that water coming from around the spark plug?

Any advice? He will most likely take it in to have looked at, but if he might just be able to put a new plate (the one in back) then he might try that first.

Thanks for any advice,

[Valv]

It could be the plate or (if you are very lucky) just the gaskets (2). Take it apart and check it out.

[Jim Uran]

cracked gasket.. Same thing happened to my old Ev.. part is pretty cheap. Mine runs great after I put a new one in.

[BoxMN]

Thanks guys, will check the plate and the gasket.

I guess he ran it this morning, and it worked great for about 10 minutes, then it shut down and would not start. Do you think it could be the case that the engine compartment filled with ater from the leak (they are not designed to drain, are they?) and created a short or just got the ignition wet?

Thanks again,

[marine_man]

Quote:

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the engine compartment filled with water from the leak (they are not designed to drain, are they?)

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Tough to say what the issue is - but the lower engine cowling is designed to drain.

marine_man

[BoxMN]

Thanks MM,

I know on my old Evinrude, when I had a x-ducer mounted wrongand it would spray all over the cowling, it would get wet inside and kill the engine. Hoping that is what is happening to him, and the gasket/plate will solve his problem. I also saw several wires inside the engine compartment that were coroded and looking pretty bad.

[boatfixer]

Cover plate gasket more than likely. Fairly common, simple fix.

[wishing for walleyes]

I just replaced my gasket last week on my 40 HP 4 stroke mercury.It was leaking just below the top spark plug.The gasket was $8.60

[BoxMN]

Thanks everybody, his is the gasket. I didn't realize how common this is. Very good to know, as I have a couple older motors. But I see it even happens on newer ones.

I must say, this FM forum had it nailed right away, very impressive knowledge here - thanks everybody for sharing your skills and experience!