1984 50 hp Mercury Water in #1 Cylinder

R B

Seaman
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Feb 18, 2013
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Engine lacks for power and I found water coming out of the #1 (top) cylinder plug. What should I look for before I pull the engine apart for repairs?
 

Bosunsmate

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Re: 1984 50 hp Mercury Water in #1 Cylinder

Have you done a compression test?
Id start on the cylinder head water gasket and then if that doesnt fit it check the exhaust gasket/plates
 

R B

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Re: 1984 50 hp Mercury Water in #1 Cylinder

All 4 test at 120 psi. I have a repair manual but I didn't see anything about a cylinder head water gasket.
 

Bosunsmate

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Re: 1984 50 hp Mercury Water in #1 Cylinder

Maybe im looking at the wrong model, is yours 4cyl? Sometimes its called a watercover gasket
Is there a headgasket on this one instead?
 

emckelvy

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Re: 1984 50 hp Mercury Water in #1 Cylinder

If it's coming from the area where the cyl block water jacket cover seals around the spark plug holes, it's just a leaky gasket that can be replaced.

You do need to be careful when removing the 1/4-28 bolts as they have a tendency to seize in the block and snap off if too much force is used. Instead, use a heat followed by penetrating oil (as required). A propane or MAPP portable torch should have plenty of power for this job.

The gasket you need is Merc P/N 85487.

If you're in a pinch and have to get it out on the water, just clean around the leaking area and temporarily seal it with red hi-temp RTV sealer.

HTH...........ed
 

Chinewalker

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Re: 1984 50 hp Mercury Water in #1 Cylinder

Okay - subject says water IN cylinder and later you say water coming OUT of cylinder. Makes a big difference as to where you're findi g the water.
 

Faztbullet

Supreme Mariner
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Mar 2, 2008
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15,589
Re: 1984 50 hp Mercury Water in #1 Cylinder

Agree with Chinewalker...water in cylinder= exhaust cover problem or reed...outside = water jacket gasket
 

R B

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Re: 1984 50 hp Mercury Water in #1 Cylinder

I originally said water in cylinder as I believed water was being pushed out what looked like from the spark plug. Al this information is very helpful as I am noe believing it may just me the cover gasket. The next step should be to remove the water jacket cover to check the gasket.

No head gasket on this engine.
 

Bosunsmate

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Re: 1984 50 hp Mercury Water in #1 Cylinder

Yep most likely the water cover gasket. Have a look at your spark plug, is it similar in colour to the others?
 

R B

Seaman
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Re: 1984 50 hp Mercury Water in #1 Cylinder

I installed new plugs a couple of weeks ago just because the boat is new to me. I pulled the water cover off and the gasket is definitely in need of replacement. Would the water getting out by the plug cause the motor to run poorly? Especially at wot?
 

Bosunsmate

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Re: 1984 50 hp Mercury Water in #1 Cylinder

I installed new plugs a couple of weeks ago just because the boat is new to me. I pulled the water cover off and the gasket is definitely in need of replacement. Would the water getting out by the plug cause the motor to run poorly? Especially at wot?

Yep the plugs will short to ground via the water
 

R B

Seaman
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Feb 18, 2013
Messages
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Re: 1984 50 hp Mercury Water in #1 Cylinder

Not a bad job to replace the water cover gasket. I was so excited to think I would be finished and ready to go boating. Went to start the motor and it fired for a split second right away and then it just cranked and cranked and........... You probably get the picture by now. Looking for a fresh start tomorrow before I start throwing my tools!

Any help again would be appreciated. So far everyone has been very helpful and I thank you! I don't remember becoming a boat motor mechanic when I bought this but I must say that I have learned a lot!
 
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