cylinder leaking in 74 merc

[gustafsonerik]

cylinder 4 is leaking in water i was wondering what could it be other than a cracked head where to start

 

[timmathis]

Re: cylinder leaking in 74 merc

What HP?
Probably you will have to tear it down to tell for sure.

 

[Plainsman]

Re: cylinder leaking in 74 merc

I had the same question for the # 1 and was told it was the water jacket. Of course, without looking I can't be sure.

 

[AMD Rules]

Re: cylinder leaking in 74 merc

Erik, I am assuming this is a 74/75 Mercury 4cyl 500 (50hp) as some of your other posts indicated.

If you see signs of water IN the cylinder:

You could have a failed exhaust baffle allowing water into the cylinder.

You could have a cracked cylinder dome (block) on the water jacket side (your motor does not have a removeable cylinder head).

Most likely, you have a failing seal on the lower end of your crank shaft allowing water into the lowest (#4) cylinder.

If you see signs of water AROUND the spark plug:

You likely have a failed water jacket gasket. This is a common source of water leaking externally. The fix is relatively easy, but you need to make sure the cause was not an overheat. If it was, solve your overheat situation before continuing.

 

[Clams Canino]

Re: cylinder leaking in 74 merc

Correct... external leaking around the plugs is a minor problem. There no removable head, just a waterjacket cover.

Tim... in 1974, the HP is irrelevant to the question, they ALL used the same block and cover design, only the cylinder count and HP was different.

-W