Mercruiser 4.3…Milky oil coming from timing cover.

[Scott Danforth]

Which drain is this?

the 1996 and later 4.3's have 5 drain plugs. 2 block, 2 exhaust manifold, 1 in the thermostat housing on the intake manifold. that one gets missed

 

[Lou C]

this one....
the Pre-Vortec engines did not have this, I'm not sure what they changed to make that a necessity on the Vortec...

 

[Thomas E]

If there is water behind the timing cover, there is water in the pan.

Might pull a breather tube off a valve cover and see if there is white foamy stuff on the underside. Note that the dipstick will not see water - oil floats and water is at bottom, so when you pull the dipstick it will look clean. Only good way to know if there is water is to drain the oil or use a vacuum to pull some off the bottom of the pan.

Going to try and check the oil today when I get home. Does the dipstick tube run to the bottom of the sump? Or close enough to see the water if I vacuum it out of the dipstick?

 

[nola mike]

this one....
the Pre-Vortec engines did not have this, I'm not sure what they changed to make that a necessity on the Vortec...

Yeah, we've had this discussion before. It isn't necessary to drain, none of the service manuals (that I can find) mention it, that space is cavernous and drains (almost?) completely when you pull the t stat hose. Someone prove me wrong (@Scott Danforth )

 

[Lou C]

I recall our discussion, yep, the only thing I can say is that I found an OMC Cobra service bulletin that said that under certain conditions freeze damage can occur if you don't drain it. Having never had one, I can't say and for sure on the older pre Vortecs as soon as you pull the bottom of big hose on the circulating pump the whole thing drains. Not sure what they changed, that could make a difference.

 

[nola mike]

I recall our discussion, yep, the only thing I can say is that I found an OMC Cobra service bulletin that said that under certain conditions freeze damage can occur if you don't drain it. Having never had one, I can't say and for sure on the older pre Vortecs as soon as you pull the bottom of big hose on the circulating pump the whole thing drains. Not sure what they changed, that could make a difference.

I've pulled that plug a few times now, always bone dry. And even if there was water in there, there's plenty of expansion room. You got a copy of that bulletin?

 

[Lou C]

I looked but that service bulletin is gone from the 'net but I did find this:

Volvo penta 4.3l GL-J, raw water drain locations? (pics)

Money is tight with neededing new tires for my truck and other unforeseen bills so I want to save myself the $250 winterization fees this year. I've read the sticky and several other posts pertaining to winterizing but trying to not purchased the expensive shop manual. I've poked around the...

forums.iboats.com

 

[dubs283]

Yeah, we've had this discussion before. It isn't necessary to drain, none of the service manuals (that I can find) mention it, that space is cavernous and drains (almost?) completely when you pull the t stat hose. Someone prove me wrong (@Scott Danforth )

Not going to prove you wrong, because you are not. I will share an experiment I performed several years ago.

During winterizing I chose four 4.3 engines with intake drain plugs, two Volvo, two mercruisers.

The first mercruiser I opened the intake drain first, water gushed out, maybe a pint or more. Then I drained block/manifolds. Second mercuiser I drained block/manifolds first then the intake, only a trickle of water emerged.

Volvo I performed the same test, first the intake, water gushed out. Second Volvo I drained the intake last and while not gushing out enough water drained that in my opinion it was possible to cause freeze damage if left in the intake.

I have never seen a mercuiser intake with freeze damage, while I have seen more than ten Volvo intakes with freeze damage, ymmv

 

[achris]

Yeah, we've had this discussion before. It isn't necessary to drain, none of the service manuals (that I can find) mention it, that space is cavernous and drains (almost?) completely when you pull the t stat hose. Someone prove me wrong (@Scott Danforth )

I can prove you right.
When I got my first V6 I was skeptical about the dipstick tube, so when I needed to change the oil, I sucked it out as per the book, then dropped the pan drain plug. Not a drop!

Chris......

 

[Lou C]

The only thing I can think of is that if the boat is stored tilting a certain way (let’s say lower on the starboard side) maybe enough water can collect to cause cracks.
Also:
If you look at the bottom of the pre Vortec & Vortec you see differences:
The pre Vortec has a very small water passage and the exhaust crossover passage under the carb
The Vortec has a much larger water passage that appears to extend under the carb perhaps to heat the area under the carb for cool weather running. I’m thinking this may make a difference?