Serious Engine Knock!

J

jmicara

Cadet
Joined
Aug 31, 2007
Messages
12
I have a 5.7 Mercruiser and it has developed quite a knocking sound. It puffs smoke through the carburetor and I though it was mis-firing so I changed all the plugs, wiring, rotor and cap. I seem to have water in the oil because the oil is a nice coffee color on the dip stick, as well as leak into the bilge with the same color. I tried marvel mystery oil hoping to lubricate and free up anything that was stuck but no good. I checked compression on all chambers and the are all within range 145-150.

The sound is definitely coming from the top as of the engine. I need to figure out if the rod it bent or broken or something else. I''m thinking of pulling off the cover and cranking it to see if I can see what is moving and what's not. Not sure how much oil will leak out though.

I then need to find out why the water is mixing with the oil and where it is leaking from. Riser, manifold...who knows. Fun, fun, fun.

Any and all help is greatly appreciated.

Joe
 
J

jmicara

Cadet
Joined
Aug 31, 2007
Messages
12
Re: Serious Engine Knock!

I forgot to mention I checked the water coming from the outdrive pump by disconnecting the hose while it was running and the water and pressure were fine. I also changed the thermostat because this problem originally happened while I was going 5mph through a canal and I started to overheat. Then the knocking started.....actually sounded like fire crackers. The knocking goes faster with higher rpms and slower with low rpms. Other posts seem to indicate piston skirt problem with overheating. Then also state I can run the engine like this with no other problems other then the annoying sound. Does that sound correct? I'm just trying to get through the Stripped Bass run and I'll call it a season!

Thanks,

Joe
 
havasuboatman

havasuboatman

Ensign
Joined
Mar 5, 2009
Messages
904
Re: Serious Engine Knock!

dude, you have water in your oil, and it's leaking out into the bilge. You have a major engine problem. The firecracker noise is probably detonation due to having water in the cylinder, my guess would be a bad head gasket.
the backfiring thru the carb, assuming the engine timing is correct, is indicitive of a bent or burned valve.
 
J

jmicara

Cadet
Joined
Aug 31, 2007
Messages
12
Re: Serious Engine Knock!

I opened the value cover and found one of the rockers (3rd from the back of the boat) was not moving. I removed the rocker and found the push rod bent. I am assuming that was where the firecracker knocking sound was coming from. So it appeared the lifter was stuck. An old marine mechanic told me to soak it with WD-40 and PB Penetrating lube and then to hit it with a rubber hammer and a block of wood to dislodge it. Well, I hit it and the spring went down but never came back up. I store the boat on the side of my house and was wondering if this is a project I can fix during the winter/early spring time frame. I do not have the ability to lift the engine out and was hoping this can be fixing in place but I do not see any references to stuck lifters and how to fix.

Any and all help is greatly appreciated!

Joe
 
ziggy

ziggy

Admiral
Joined
Jun 30, 2004
Messages
7,473
Re: Serious Engine Knock!

this is way to late to post this, but here it is..

http://www.boatfix.com/merc/Bullet/01/01_13.pdf

hope ya changed the oil back in oct. immediately after ya found water in the oil. if ya didn't get the oil changed back in oct. i'd think yer hosed. as in pull the engine + rebuild it.. the way i understand it, time is of the essence when ya have water intrusion...

just my wag... hope i ain't right and good luck with her...
 
boat1010

boat1010

Senior Chief Petty Officer
Joined
Mar 10, 2009
Messages
781
Re: Serious Engine Knock!

I'm thinking you have more than one problem. The knock could be a few things. I just had the crank break on my 454. Bad sounds... But the water in the oil can be a cracked block or head gasket. But if it were the head gasket you should be able to see the oil run down the side of the motor to get to the bilge. If a rod broke it could have punched a hole in the motor. But you need to find out where the water is getting into the motor from. And not good to let it set over the winter with the water in the oil. You can remove the valve covers and run it for a short period and not have too much oil leak out.
 
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