Head Gasket failure- 4.3 OMC

[trunctj]

I was running my 4.3 OMC at 2800 rpm, when I heard some clacking (like a broken belt smacking a solid surface). I throttled back, lifted the cover and saw the breather tube spewing out oil/water mixture. Was close to the marina and tried to make a run for it, but no luck. Ran for about 30 seconds, and then it just bogged down and stalled.

Removed the valve covers- nasty mess. Ran some kerosene thru the engine a few times to try to clean out the saltwater/oil "cake batter" that had formed. Put some clean oil in just to purge the kerosene, and started up the engine. Ran it at idle for a minute without water on. Shut it down, drained the oil again. Replaced oil and filter again, but couldn't start it. It turned over with difficulty even with the plugs pulled. I don't think I did damage running kerosene and oil thru it for short periods. Not sure why so stiff now.

Haven't tested compression yet. Assume I have blown head gasket.
Anyone else experience this?

 

[Alpheus]

Re: Head Gasket failure- 4.3 OMC

Ran it at idle for a minute without water on.

Its stiff because you ran with no cooling and with "thinned out oil" You probably damaged your bearings and your crank journal surfaces...

 

[trunctj]

Re: Head Gasket failure- 4.3 OMC

I would agree about bearing damage occurring, if I ran it longer without cooling and proper lubrication. I had noticed prior to this incident, that the motor would intermittently, crank over slowly. I had attributed it to my battery wearing down. But now, I'm wondering if something else was going on.

I plan on tearing it down completely- we'll see.

 

[Howard Sterndrive]

Re: Head Gasket failure- 4.3 OMC

Assume I have blown head gasket.

I wouldn`t even really consider that.
Truth is: Head gaskets don`t actually `blow`at all.
A failed head gasket is the result of another issue, such as overheating.
I would perform a pressure test of the cooling system.

Running 1 minute with milky oil under light load would not damage any bearings.
But salt water will corrode bearings to destruction in relatively short periods of time... how long has it sat with this emulsion in it?

I had noticed prior to this incident, that the motor would intermittently, crank over slowly.

sounds like your engine was trying to tell you it was getting water in the cylinders from a failing exhaust manifold, riser, or riser gasket

I suspect the pressure test will lead you to the exhaust

Not sure why so stiff now.

suspect it`s hydrolocking from leaking exhaust filling cylinders with water. Water doesnt compress..

I hope you are on land now, doing this oil changing, running with fresh water...

If you have left it for any period of time with salt water in the cylinders, the engine will be scrap

 

[trunctj]

Re: Head Gasket failure- 4.3 OMC

First, let me say "thanks" for all the responses.

I think saltwater damage may be the issue. I notice corrosion on the visible portion of the valve springs and push rods.

The motor failed at 6:00pm. I did not drain and flush it until the following morning. So, that nasty mess sat in the crankcase for 15 hours. It had the consitency of cake batter- I was surprised at how thick it was. Very ugly.

 

[grahamh]

Re: Head Gasket failure- 4.3 OMC

I heard some clacking (like a broken belt smacking a solid surface).

I think you have a blown motor, not just just a blown head gasket.

The sound you heard sounds like a rod knock to me, probably the oil had been compromised for some time, and the motor finally gave out.