Water in Cylinder, 1979 40hp merc

[kellyisu]

I have a 79 2 stroke 40hp Mercury that started running ruff last fall when pulling up to the boat ramp. Took it home and put the hose on it and found that water was getting into one of the cylinders. Ran on one cylinder. HAven't done a compression test yet.
What are some possible causes of this? I'm not 100percent sure but im confident as of right now that the head is fine. Never ran it hard, kept oil mixture right. Is it possible a gasket finally started to out, letting water in? If so, which gasket could it be and is it a do it yourself job? I do have some mechanical skills and have rebuilt motors.
THANKS
KELLY

 

[westexasrepublic]

Re: Water in Cylinder, 1979 40hp merc

I dont think it would run at all if water was in the fuel mix during compression....what it does sound like is your water jacket cover seal is leaking around the spark plug. Its an easy DIY to replace, if the bolts that hold that plate on dont shear off...

HERES A PIC OF MY 79' 70HP 3 CYL AS A REFERENCE

 

[kellyisu]

Re: Water in Cylinder, 1979 40hp merc

westexasrepublic
Thanks for the quick response and picture to go with that. I was looking at some parts diagrams before I posted this and was wondering about that gasket as well. Very helpful post.
Again, Thank you

 

[kellyisu]

Re: Water in Cylinder, 1979 40hp merc

Does that cover come off pretty easily after I remove those bolts?

 

[westexasrepublic]

Re: Water in Cylinder, 1979 40hp merc

No problem, ill attach a better photo, you can see the sheared bolts and other mess I found once I popped that POS off.

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[kellyisu]

Re: Water in Cylinder, 1979 40hp merc

I think I'm gonna try and fix it. I was either fix it or sell it as is. I have 2 takers for $500. Although I have done alot of work to this motor and it has all new electrical components(powerbox, stator,rectifier, starter), and a few othe odds n ends. I have just had so many other projects that I didn't want to get myself in to deep in this one. ANY ADVICE?
Thankya

 

[kellyisu]

Re: Water in Cylinder, 1979 40hp merc

Quick question: If it was the water jacket cover seal, would I still get water in the one cylinder(my plug was wet)?

 

[kellyisu]

Re: Water in Cylinder, 1979 40hp merc

Anyone else have any thoughts?

 

[westexasrepublic]

Re: Water in Cylinder, 1979 40hp merc

the tip was wet? like milky, pictures...pictures....?

 

[Faztbullet]

Re: Water in Cylinder, 1979 40hp merc

If it was the water jacket cover seal, would I still get water in the one cylinder(my plug was wet)?

No.. Water can only enter cylinder several ways:
1) Hole in top of jug from erosion or mechanical failure(rod/needle brg)
2) Lower crankcase seals bad
3) Crack in fuel pump as this engine uses a water cooled pump
4) Divider plate eroded but usually affects both cylinder at idle

 

[kellyisu]

Re: Water in Cylinder, 1979 40hp merc

Wish I had pictures. I have had the motor off the boat since fall with the controls still on the boat. I was just now gettin to where I was either gonna work on it or sell it.

Yes, the plug was wet on the inside. I don't know if I would say it was milky though, but it has been several months since this occured. ( I did try and dry everything out and lubricate before winter)