Help with water in oil

[h22221]

Hi, I have a mercruiser 4.3lx 1990. Loads of water in my oil and in cylinders 2, 4 and 6, and also number 3.

I originally thought it was riser/exhaust gasket so replaced those, but still have the same problem, so I took off the starboard head and there is a hole in the exhaust port of cylinder no.2 (see photo)

Question is, this would obviously cause water in the cylinders 2 4 and 6, but would water make its way over the intake manifold exhaust cross over into cyclinder no.3? And would this hole leak that much water into the crank case etc? I am hoping it would. The block looks OK in the valley with no visible cracks, so I am hoping that a couple of new heads will sort out all this water in my oil....

Thanks

 

[Lou C]

Hard to say but if one cyl is rotted like that others could be but you might not be able to see it. What does the block deck look like? From what I’ve heard the heads rot through faster than the blocks. I had 2 blown head gaskets and remove the old heads on mine. Had them checked at a machine shop and there were cracks in the exhaust valve seats in the center cyls on both heads, from a past overheat. I replaced these with a pair of reman heads and so far so good.

 

[h22221]

Hard to say but if one cyl is rotted like that others could be but you might not be able to see it. What does the block deck look like? From what I’ve heard the heads rot through faster than the blocks. I had 2 blown head gaskets and remove the old heads on mine. Had them checked at a machine shop and there were cracks in the exhaust valve seats in the center cyls on both heads, from a past overheat. I replaced these with a pair of reman heads and so far so good.

Block looks great.... I haven't cleaned the deck up yet but will do ASAP. Boat only has 166 hours on it so surprised they've rotted like this...

I just hope that this hole is the cause of loads of water in my oil.... But assume the only way it would get into the crank case is via rings.... So worrying a bit that it could be something else as there was a lot of water in there

 

[Lou C]

You would have had water in a cyl from that, did you have misfires, reluctance starting and possible hydrolock?
With water in cyls when its just a little you start out with reluctance to start on an engine that used to start easily, then misfires till it warms up. In worse cases you get slow cranking due to partial hydrolock because of the water in a cyl.
When I had my old heads checked out, the machinist didn't find rust through yet, but the cooling passages were getting eroded and that suggested to them that after the heads were repaired they might not seal correctly on the new head gaskets so they recommended replacement which is what I did. Got a pair of reman cyl heads same casting #s and everything went back together pretty well. Just make sure that you use a thread chaser to clean out the cyl head bolt holes, and if the head bolts are really rusty replace them.
I saw rust in this intake port but it was not clear if it was starting to rust though....
and here are the reman heads....

 

[h22221]

You would have had water in a cyl from that, did you have misfires, reluctance starting and possible hydrolock?
With water in cyls when its just a little you start out with reluctance to start on an engine that used to start easily, then misfires till it warms up. In worse cases you get slow cranking due to partial hydrolock because of the water in a cyl.
When I had my old heads checked out, the machinist didn't find rust through yet, but the cooling passages were getting eroded and that suggested to them that after the heads were repaired they might not seal correctly on the new head gaskets so they recommended replacement which is what I did. Got a pair of reman cyl heads same casting #s and everything went back together pretty well. Just make sure that you use a thread chaser to clean out the cyl head bolt holes, and if the head bolts are really rusty replace them.
I saw rust in this intake port but it was not clear if it was starting to rust though....
and here are the reman heads....

Yes, definitely loads of water in cylinders.... Which i assume is from this hole which pours in when exhaust valve opens.... But wondering if that hole/water in cylinders would allow that much water into the crank case?

 

[Lou C]

the bigger cause of water in the crankcase is a rotted intake right under the thermostat housing, but if you run it long enough with water getting into cyls, even not enough to hydrolock it, there will be a fair amount of water in the oil.

 

[h22221]

the bigger cause of water in the crankcase is a rotted intake right under the thermostat housing, but if you run it long enough with water getting into cyls, even not enough to hydrolock it, there will be a fair amount of water in the oil.

I pressure tested the intake manifold today, all good. I really hope it is just that hole in the head and not a cracked block. The heads are off now so I guess no way to test the block other than filling coolant passages with water and seeing if the level goes down?

 

[Lou C]

Well while you never know, I think cracked blocks are rare except from improper winterization. My boat suffered a bad overheat in 2013, it ran fine nearly 3 more seasons then blew both head gaskets in August of 2016. When I took it apart, I had the heads checked, they found cracks in 2 cyls, center cyl exhaust valve seat area. I took really good pix of my block deck and showed it to the machinist and a good mechanic I know. Both felt it was worth trying to install the heads and see if it held water pressure. And it worked out fine. So if you always winterized yours and it never froze its probably OK. But its a gamble none the less.

 

[h22221]

Well while you never know, I think cracked blocks are rare except from improper winterization. My boat suffered a bad overheat in 2013, it ran fine nearly 3 more seasons then blew both head gaskets in August of 2016. When I took it apart, I had the heads checked, they found cracks in 2 cyls, center cyl exhaust valve seat area. I took really good pix of my block deck and showed it to the machinist and a good mechanic I know. Both felt it was worth trying to install the heads and see if it held water pressure. And it worked out fine. So if you always winterized yours and it never froze its probably OK. But its a gamble none the less.

Thanks, I only bought it a month ago, rebuilt the drive completely, ready to go out and ran it to check it all over and loads of water in the oil.... The seller had loads of receipts etc for winterising it every year, and it was winterised when I bought it, although I started it up and ran fine, but impeller was gone, so took a gamble, it was sat for nearly 2 years as well..... Was cheap enough so worth it still.

I will fill the coolant passages of the block over the weekend and have a look, but the valley looks nearly new to be honest so no visible cracks there.

I have rebuilt a couple of 350's and the only crack I saw in a cylinder was from the throttle cable getting stuck and it dropped a valve seat in cylinder no. 3....so I think I'll stick some fresh heads on and see what happens

Thanks for the help

 

[h22221]

So I took the other head off and it looks OK, the block seems OK too..... I hope!

I did stick a magnet down the cylinder water jackets and got a lot of corrosion out, but the cylinder walls seem really thick.... Hope this isn't a problem

 

[Lou C]

You can tell better after you get the old gaskets off and really clean it up. Looks like it was used in salt water.
Here's mine. At this point it was used in salt about 15 seasons worth.

 

[h22221]

Thanks, going to clean it up over the weekend, fingers crossed! And yes, it was I think, but not for the last 5 years as it was in a river

 

[Lou C]

All that rust, is why if I ever replace the engine in this one it has to have closed cooling. I just hate the idea of running raw water through a nice new cast iron engine! Plus, sticky thermostats and cold running are a more or less chronic problem I've had with raw water cooling.

 

[Scott Danforth]

this picture says the motor was once in salt water

it is also why you dont add a HX to a used motor

 

[Searay205]

Wow, I used a 3.0 liter in saltwater for 32 years!!!!! Only had manifolds rot through. I don't know if true but was told cylinder number one is thin to make room for impeller so if a 3.0 liter rust through that's where it occurs. Mine never did. Flushed every time. Shocked you are having this problem with your low hours. I always thought it was heat the expediated the corrosion.

 

[Lou C]

I changed my thermostat yesterday and drained the motor down enough to dry out & check the water passage in the intake manifold. It is surprisingly solid and this is the original intake reused when I replaced the heads 4 years ago. Now used in salt close to 20 years and never flushed during the season. It makes me think that maybe my practice of winterizing by draining and filling the engine with antifreeze with corrosion inhibitors actually helped

 

[h22221]

I think it looks worse than it is, but it is 31 years old and who knows what happened to it before me.... the cylinder walls feel pretty thick to me, I was expecting wafer thin, but they seem very thick

My plan is to spray everything inside and out with aquasteel and hope for the best with some new heads!

Then after every use I will be flushing with oily water to try to prevent it getting any worse

 

[Searay205]

I think the key (what do i know) is to keep the block full of water or antifreeze at all times, winter included! Oxygen content in water is neglible compared to air (oxygen, water, cast iron are needed for corrosion we remove one and corrosion stops). When the block is drained it takes a year for it to dry out and in that time corrosion is having a field day, damp cast iron and oxygen rich air.

I live in Houston so little risk to freezing except this year. I drained the day before the freeze and started up a week later to refill block.

 

[Lou C]

What I’ve seen:
Every year at winterization I’ve filled it with AF, either the best -100 or mixed up a batch of Sierra no tox AF. At first start up in spring first AF comes out the exhaust then clear water no rust. That’s what makes me think it made a difference. And the fact the the water passage in the intake is still solid no big chunks coming off.

 

[Searay205]

I filled mine with used motor oil one year over winter. Pretty sure that winter it didn't corrode....