Milky oil :'-(

Good Grief

Good Grief

New Member
Mar 26, 2008
314
Lusby, MD
Boat Info
290 Sundancer 1998
Engines
4.3L V-6's w/ Alpha 1 Gen 2 drives
I finally got around to changing the oil today and discovered the port motor oil is milky. A golden tan. I don't think there was much water in it as there was only 4-5 quarts once the engine was drained. I guess its time to start trouble shooting.

The boat had been blocked and wrapped all winter. No problems when I put it up. The boat idled from winter storage to the slip (less than a mile). No unusual sounds but the temperature indicator did act funny when it was started. It would cycle between the low peg and about 150 degrees but once out in the creek and in gear it stabilized out and ran at 165F (normal). I picked up an alarm on this motor (NOT oil pressure, normal operating temperature) while idling at about 1000 RPM. I shut it off then restarted it (with no problems) prior to docking about 10 minutes later. I have been unable to recreate the alarm at idle in the slip.

The motor has run a total of about 50 minutes (all </= 1000 RPM) since launched.

In any case, how do I go about trouble shooting why I have water in the oil.

Thanks in advance.
 
first suspect would be the head gasket.....about the only way water can get into it that I know of.....other than a cracked block.....which would also cause the engine to run hot and a lot more noticeable.....
 
I would think it's a head gasket. Usually if the block cracks on a GM it leaks externaly. You could have a cracked head but it can and should be checked if you replace the head gasket.
 
if you called me and told me your symptoms, i would show up with a leak down test. I would air up each cylinder and look for leak down. these are some of the things I have seen in the past on GM engines. cracked head, no water going into crankcase but engine would overheat...cracked block, fill real quick with water until milkshake and overfill crank,
i would suggest water may have entered thru the exhaust manifolds and seaped past the rings and into the crank, but if its saltwater it usually will sieze the pistons but in your case if the boat was winterized it will be anti-freeze and this wont corrode....did the engine turn over slow at first?
diagnosing is key but a sure 100% method to find the problem is a leakdown test or compression test....its cheaper than assuming because it may be something simple
 
No difficulty starting the engine. My plan is to pull the plugs and look in the cylinders and fog/oil them. The crankcase did not fill very quickly based on the amount of fluid i took out. I am hesitant to start the engine w/ fresh oil in it so as not to compound the problem. Right now I do not believe I have any internal engine damage, aside from the source of water intrusion. After researching and mulling this over in my mind (all night...). I came to the same conclusion on the exhaust manifolds and that I have been fortunate enough to catch it at the onset vice when the motor freezes while on plane. What do I need to do a leak down test?
 
could the winterization have not been done properly? If water in the block froze that may have been a cause... When was the last time you changer your manifolds and risers??? Water could get in the engine throught exhaust...
 
OK, tonight I checked the compression, 5 of the 6 cylinders were 175-185 # the 6th cylinder, port side aft was 125#. I squirted oil in the cylinder, did a 2nd check and the compression went to 165#. It doesn't tell me where the water is coming from but it does indicate that cylinder is scored or needs rings. The manual says that if the lowest pressure is within 75% of the highest pressure it is OK. 75% of 185# is 139#. Now can I run with this for a season and have the motor worked come winter or should I have the cylinder repaired now? Tomorrow I'm going to run the motor again and see what I get. For those suffering from a similar issue or looking for guidance. The Mercruiser bulletin is here http://www.*******.com/merc/Bullet/01/01_13.pdf
 
I am suffering with the same issue. The link you posted is bad. I hope you have an easy and affordable fix and your back on the water soon. Best of luck and keep us posted on your progress. Still sounds like a head gasket to me.
 
Last edited:
kg4vgh said:
first suspect would be the head gasket.....about the only way water can get into it that I know of.....other than a cracked block.....which would also cause the engine to run hot and a lot more noticeable.....
Click to expand...

Don't overlook the intake manifold gasket. Water travels from the cylinder heads to the intake to get to the thermostat housing.
 
for anyone still following this thread... replacing the manifolds, spacers and risers appears to have fixed the problem. I have not sea trialed the boat yet but have run it pier side from idle to 2000 rpm for extended periods with success. I did discover that the manifold bolts were not at spec of 25 ft-lbs during the removal and looked like water was seeping in through the center (v-6) exhaust port.
 
Glad to see things are working out.
 
In autos of that generation, the v6 used a plastic and rubber or neoprene type intake manifold gasket. I am not experienced with marine engines, but note this for consideration. the gasket would leak internally only during an engine warm up then cool down cycle. Typically and most noticeably during colder weather. So on an unpressurized marine engine during warmer weather you may not see it. One possible indicator is if it is also leaking externally. Look for staining at the corners of the intake where it meets the block.
 
does new oil have water in it now that it has run. could the oil been contaminated when it was changed last year. or could it be condinsation from storage?
 
The oil DOES NOT have any water contamination in it now. When I discovered the oil, I replaced it, ran motor, found oil in same, water contaminated condition, changed oil again, ran motor again with same results. Replaced manifolds, spacers and risers, changed oil, ran motor, a couple times... Good to go!!
 
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