Mysterious leak origin?

[seamanben]

'98 3.0L Mercruiser, 135hp, operated in salt water 9 months of the year. 5 Pictures attached.

I'm not sure where this leak is coming from. There's marks over and around the push rod cover where rusty water has flowed. There's a line of rust all along the big gasket in the pictures (the head gasket I believe) where I think the leak is coming from. But why would salt water be coming through that gasket when it's supposed to be isolated in the exhaust manifold area?

There's also a little bit of rusty water around the two spark plugs closest to the stern. I pulled the plugs and there is no rust on the threads, just in the little recessed plug well. Any ideas how this got there?

I've removed the push rod cover to get a better look at the area, and I've taken some pictures. (these pics are of the Starboard side of the engine).

Any help is much appreciated!

 

[Bondo]

Re: Mysterious leak origin?

Ayuh,... From your limited pictures,...
It appears the water is being sprayed onto the motor from above...

 

[a70eliminator]

Re: Mysterious leak origin?

Looks like typical surface oxidation caused by condensation, clean and repaint.

 

[seamanben]

Re: Mysterious leak origin?

Thanks for the quick replies.

Bondo - there's no sign of water marks above the spark plugs, that's why I don't think it's from above. Plus, the rust line is all along the edge of that gasket, and in those two plugs, nowhere else... I do have a good engine cover so water shouldn't get through. Would fresh water cause it to rust that much?

Eliminator - if it were just condensation, wouldn't the two spark plug wells closest the bow-end of the motor also have rust (they don't) ? I'll clean it up with a scrubby, sand a little, and spray with Super Enamel. Is that what you'd do?

Thanks

 

[Bondo]

Re: Mysterious leak origin?

Bondo - there's no sign of water marks above the spark plugs, that's why I don't think it's from above. Plus, the rust line is all along the edge of that gasket, and in those two plugs, nowhere else... I do have a good engine cover so water shouldn't get through. Would fresh water cause it to rust that much?

Ayuh,.... Water flows Downhill,.... If the headgasket was leaking, the water Can't get Up to the sparkplugs...
The block Deck, where you see the rust is just a Shelf that's catching,+ holding the water,...
Hence, the Rust....

It could be coming down through the motorbox,... I Donno,.. I can't see it...

 

[JustJason]

Re: Mysterious leak origin?

it makes a mess but you could blow some talcum powder on the side of the block, take it for a quick run, pull back the hatch and look. The water tracing in the powder will show instant results vs waiting for painted iron to rust.

 

[seamanben]

Re: Mysterious leak origin?

it makes a mess but you could blow some talcum powder on the side of the block, take it for a quick run, pull back the hatch and look. The water tracing in the powder will show instant results vs waiting for painted iron to rust.

Sounds like a good idea Jason, thanks I'll do that.

 

[CheapboatKev]

Re: Mysterious leak origin?

If it is as simple as external water and not anything internal..

I spray my engine block occasionally with WD40 to help ward off the rust gremlins

 

[seamanben]

Re: Mysterious leak origin?

If it is as simple as external water and not anything internal..

I spray my engine block occasionally with WD40 to help ward off the rust gremlins

won't this loosen the gasket seals?

 

[Bondo]

Re: Mysterious leak origin?

won't this loosen the gasket seals?

Nope,... Not near as much as pulling the side-covers for no reason at all....

 

[seamanben]

Re: Mysterious leak origin?

Nope,... Not near as much as pulling the side-covers for no reason at all....

haha, good one.

 

[fat fanny]

Re: Mysterious leak origin?

I got that type of rust in the same places and found that it was caused fom my bimini top the staorage compartment is just above and behind the dog house cover the small amount of water ran down the shelf it rests on and onto the engine took awhile to figure out where it came from.

 

[Simoniz]

Re: Mysterious leak origin?

Relax, Man.

My motor is the same, simply water, probably condensation, forming on the engine and dripping onto it from above. If you have any water sloshing around in the bilge, it'll be salty and somehow, salt is carried in condensation.

Rinse with fresh water and spray with WD40.

Another tip; replace those spark plugs at least once a year. Otherwise the plug will fail due to rusting, with a noise like a bomb going off. You'll then be left hoping you can get the rest of the plug out of the cyl head with an easy out (like I was a couple of years ago!)