455 old motor, watter

Hey guys I'm new here got my first jet boat two weeks ago. Took it out the first day I got her. And went home the same day from Laughlin.

Well I'm working in her and changed out the exhaust gasket cause they where bad. And when I pulled the dip stick out I noticed that their was like a milky sludge on the bottom and water on the dip stick also. What does this mean?

Any help would be appreciated thank you!


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455s are touchy about water pressure and flow. You need enough flow to cool the motor but you can easily puch intake gaskets if there is too much pressure. If you try to turn your intake gate valve down to minimize the flow/ pressure you can run into overheating the heads. Olds are cool and nastalgic but there is a reason evwryone switches to ford/chevy. Also, 455s have an oiling issue. I'm sure more peeps will comment on that. Main crank oil ports need restrictors to keep oil on the top end. Don't over rev the motor. Another reason people switch is that olds don't like high rpm.  Glad you are coming into our family and be free to ask questions. The guys on here are awesome and full of knowledge. The problem you are having could be either and intake gasket or head gasket. Pull the spark plugs and check em out. Also look at the exhaust ports. This will tell you if it's intake or head gaskets. Good luck bro.

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Person before me had it all gone through, but in roller rockers. Mild cam, bored .30 over. And drilled out the oil pan I think it was so the oil goes all through.
I'll check the plugs out tomorrow.




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Possibly intake gasket or manifold gasket as 461 said, upload some pictures of how milky it is... What RPM were you hitting when you took it out? How long were you in that rpm range? Was the oil milky prior to you taking it out?
On an olds it's very nice to have a water pressure gauge on top of the intake so you can get water pressure dialed while keeping an eye on the temp guage...
I run 5 psi at 3000 and 12 psi at 5200, while staying at 150 degrees cruising and 170-175 at idle..


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Thanks guys for the info! I think I might know the problem I have to pull the valve covers off and clean them. Might have got some condensation. Got some new gaskets and will be changing them out tonight hopefully


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Thanks guys for the info! I think I might know the problem I have to pull the valve covers off and clean them. Might have got some condensation. Got some new gaskets and will be changing them out tonight hopefully

You might consider a compression test to rule out a blown head gasket...This will give you a basic idea of the condition of your engine.....-Rich

I did a leak down and compression test when I kept getting water in the oil, all tests showed no leaks.. Ended up being a bad machine job on the heads and wasn't getting a good seal as soon as the motor would heat up... If you look above the water jackets you can see where the water was pushing through.


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