3.0 with knock any rpm above idle

[ddttm]

I have a 2000 sea ray 180 with a 3.0L Mercruiser. I was out all weekend with it and she ran great until I was driving back to the launch and I had a sudden loss of oil pressure then it came right back up to 40lbs the RPM's also dipped but did not return to full throttle. The temperature gauge was around 180. I started to hear a knock so I slowed the engine to an idle and lifted to cover, the knock went away at idle. Then she stalled and would not start, after she stalled, I heard a gurgling noise like water boiling. I got towed in and then had a wheel bearing blowup on the way home, it wasn't a good day.

Got the boat home and it starts with earmuffs. I think I have a bad thermostat but the knock is still there at anything above idle. I pulled the valve cover and everything looks ok but I heard from friends that a tiny bent push rod would cause a knock. The knock is really loud and like I said, it does not knock at idle and purrrrrs like a kitten.

Any other ideas anyone, anyone gone through this? I am looking for advice; this is my first boat (besides my tiny sailboat).

Dan

 

[oldjeep]

Re: 3.0 with knock any rpm above idle

If you hadn't said anything about the oil pressure drop then I would be thinking sticky lifter.

Why do you think the tstat is bad? Has it been running hot? The gurgling/boiling noise would be normal for an open system when you shut it down hot.

 

[Don S]

Re: 3.0 with knock any rpm above idle

Get a mechanics stethoscope and see if you can pinpoint where the sound is the loudest.
Was it a knock or just a ticking sound?

 

[ddttm]

Re: 3.0 with knock any rpm above idle

Got a scope, it is in the head, loudest near at the front cylinder (closest to water pump). It is a tick, now does it at idle but fairly faint, louder as rpms come up. What would you do first, just check clearances or take head off? I wish I had a borescope to look inside the cylinder first but unless the auto parts store has one for rent, I don't think I'll be able to get one.

The comment about the gurgling is a relief, although when it quit on the lake the temperature on the gauge continued to rise after the engine was (up to 200) off like heat was being conducted away by metal contact instead of water temperature.

Thanks for the help guys, if I do not hear from you, Ill probably be taking the head off.

Dan

 

[Don S]

Re: 3.0 with knock any rpm above idle

Is your oil level over full?

 

[oldjeep]

Re: 3.0 with knock any rpm above idle

The comment about the gurgling is a relief, although when it quit on the lake the temperature on the gauge continued to rise after the engine was (up to 200) off like heat was being conducted away by metal contact instead of water temperature.
Dan

Also normal since the water is no longer circulating - same thing happens in a car if you ever watch the temp guage after the motor is shut off.

 

[ddttm]

Re: 3.0 with knock any rpm above idle

Oil level is right at the all the way full mark.