500 Caddy milky oil?

L

Lll122

Member
I recently acquired a project airboat with a 500 Caddy dd. I have a lot of work to do to it including installing new poly on the bottom, but I’d like to get the engine going first before I sink too much money into it . The boat has been sitting a while, the engine starts and runs, but the engine oil is milky. I drained oil and refilled, but I’m assuming it has a coolant leak somewhere. Any suggestions for a likely cause of the water intrusion, or what I should check first? Are there common issues with these motors that could cause this? I plan on doing a leak down test on the cylinders, and pulling the intake and changing gaskets….

The engine does not smoke and I don’t notice any bubbling in the coolant…


Any help or tips would be appreciated!
 
First question is how milky and have you flushed it and changed the oil ?

There can be 5-10 actual issues that cause it but if the boat has been sitting it can be as simple as a cold runner and humidity.

Flush it with a little diesel and start fresh
 
Lll122 said:
I recently acquired a project airboat with a 500 Caddy dd. I have a lot of work to do to it including installing new poly on the bottom, but I’d like to get the engine going first before I sink too much money into it . The boat has been sitting a while, the engine starts and runs, but the engine oil is milky. I drained oil and refilled, but I’m assuming it has a coolant leak somewhere. Any suggestions for a likely cause of the water intrusion, or what I should check first? Are there common issues with these motors that could cause this? I plan on doing a leak down test on the cylinders, and pulling the intake and changing gaskets….

The engine does not smoke and I don’t notice any bubbling in the coolant…


Any help or tips would be appreciated!
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I had one like that and we just drained the oil and struck out.. was the carb covered ?
 
Almost every stock intake I took off had valley pan issues.


Never had any water intrusion issue, but did have milky residue on the underside of my valve covers. I was worse when I ran Penn Grade oil for some reason. Motor always ran great.
 
One Eyed Gator said:
Almost every stock intake I took off had valley pan issues.


Never had any water intrusion issue, but did have milky residue on the underside of my valve covers. I was worse when I ran Penn Grade oil for some reason. Motor always ran great.
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The Penn grade if I remember correctly is non detergent so the moisture will go to the highest point of the crankcase and gather.
Detergent oil will mix the moisture, hence the clouding.
Sounds like a higher temp thermostat is in order.
 
John Fenner said:
The Penn grade if I remember correctly is non detergent so the moisture will go to the highest point of the crankcase and gather.
Detergent oil will mix the moisture, hence the clouding.
Sounds like a higher temp thermostat is in order.
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Thanks John never realized that about the penn grade. Always enjoy your factual responses.

That caddy was 4 motors ago, still taking baby steps to more HP lol.
 
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