mercruiser 3.0 water in oil

hello everybody,

I recently bought an older 81 charger open bow with the hopes of restoring it. The person that had it did not know much about it because they received it in trade for some work. I only gave him $400 bucks for it. It was stored outside and has a good floor carpet and hull. The seats are shot and need recovered. Not a big deal to me to redo the seats. It has a merc 3.0 inboard with an alpha 1 outdrive.

I brought it home and started to go through it and winterize it. There wasnt any water in it, and the lower unit was drained. I installed lower unit oil and changed the engine oil. I removed the line to the fuel tank to put in a gas can for starting because I dont want to trust whatever may be left in the gas tank.

I started it up just fine. It idles good, and will throttle up a bit fine. after about 20 mins I shut it down and checked the oil and found it milky. There is no rust on the block and it did not leak or show any signs of an exterior crack. This is a big disapointment. I was asured that the engine was good. I want to try an fix it myself because I cant afford to replace the engine, especialy on an older boat like this that needs other work still.

I went ahead and finished winterizing it to try and preserve it for now. I did fill it with antifreeze so I cant realy do anything with it till spring, but I am trying to figure out what to do then. I have read some posting and researched a bit but wonder if anyone else can add some advise or insite to my repair plans?

If I have researched correctly there can be several causes.

1. cracked internal block, or cracked cooling jacket.
2. cracked head
3. blown head gasket
4. intake ?

I plan to drain anitfreeze and run a compression test to check for a week cylinder. After this I plan to perform a cooling system presure test and remove the plugs one at a time if leaking to help identify wich cylinder is the problem. Then I will work to remove the head to replace the head gasket and inspect the head.

When I check the intake what should I be looking for, besides water leakage?

is there anything else I should be doing or look into??

Re: mercruiser 3.0 water in oil

There is another way water can get in your oil. When I bought my used boat with a 3.0 I found water in the oil. I also found water in the trim pump reservoir. I found out the previous owner had left it uncovered in the rain on the trailer with the drain plug in. Water filled the back of the boat and it got in through the dip stick.

I was given some different solutions. One was to pour diesel fuel into the oil fill and drain. Others that had done that said it caused more problems. I decided to change the oil and filter. Run it for 10-15 min., drain and repeat.

This might not be how you got water in your oil, but I would try changing the oil and running it for some time to see if the water returns before tearing apart the engine.

Re: mercruiser 3.0 water in oil

I just remembered something. When I found that water in my oil, it was full of water all the way up to the top of the dip stick. I think I drained out about 4 gallons of water/oil mixture. So if you have that much water in there it would probably be a good indication your engine was under water. Good luck.

Re: mercruiser 3.0 water in oil

thanks for your reply.

I wondered if the water was just there from being stored. I cant say how long it sat, but the plug was removed.

when I drained the oil in it, it was nasty and there was about 4 quarts worth of mostly oil. I then changed it and the filter. I have not drained the oil I just put in. i did check the oil after a fresh fill and it was difficult to tell if I have water or oil on the dip stick. It feels like oil, but looks like water. I have not let any of the fresh oil out of the plug, but I am sure it is milky just the same.
When I opened the oil fill cap on the top valve cover i could see some standing milky oil inside.

When I ran it it did not have a thermastat in it. It did get warm, but never hot enough to where I couldnt touch it. So I could just run it awhile to get hot and and change the oil again. I was wondering about condensation that may have been trapped from sitting? But I wouldnt know for sure.

It sucks that its winterized, because i want to work on it now!

Re: mercruiser 3.0 water in oil

I am going to tell you what you don't want to hear.

You probably have a cracked block. If the oil had no water in it when you drained it out the first time there wouldn't be enough water to turn your new oil into a milkshake.

You need to get that oil out of there and flush out your engine just in case. You are going to get all of the internals covered in rust. so even if you do find a good used block your head and rotating assembly will be junk come spring.

You also need to get the AF out of your engine. If it is cracked you are just letting it seep into your oil valley anyways.

Pressure test the blocks cooling system should be your first step before tearing anything apart...

Re: mercruiser 3.0 water in oil

Alpheus said:

I am going to tell you what you don't want to hear.

You probably have a cracked block. If the oil had no water in it when you drained it out the first time there wouldn't be enough water to turn your new oil into a milkshake.

You need to get that oil out of there and flush out your engine just in case. You are going to get all of the internals covered in rust. so even if you do find a good used block your head and rotating assembly will be junk come spring.

You also need to get the AF out of your engine. If it is cracked you are just letting it seep into your oil valley anyways.

Pressure test the blocks cooling system should be your first step before tearing anything apart...

Click to expand...

I should go ahead and drain the oil and AF then until I am ready to work on it?

I do have a question here about doing a preasure test. If the head gasket is bad wont a preasure test have a leak?

Re: mercruiser 3.0 water in oil

I was also wondering if there are any other drain cocks I might be missing to drain the water/AF i know of the lower block side, upper on bottom of exhst manifold, and one on top of exhst manifold?

Re: mercruiser 3.0 water in oil

If the head gasket is blown (doubtful) yes it will leak there. Block off all of the pertinant hoses using hose clamps and pieces of dowel rod,broomstick or whatever will seal up the hose. Introduce 10psi of air into the cooling system and listen for a leak. It should be a sealed system.

Every 3.0 I have seen has 2 drains on the port side of engine.

Re: mercruiser 3.0 water in oil

If the head gasket is bad wont a preasure test have a leak?

Click to expand...

Ayuh,.... That's the Whole Idea of a Pressure Test....
You'll Hear the leak, then follow the sound...

Which sparkplug hole,..??
Oil filler cap,..??
Valvecover vent,..??
Carb throat,..?? Exhaust,..??

It gives you a direction to Go, not necessarily the actual Problem, until further tear-down...

Re: mercruiser 3.0 water in oil

ok those are the two drains I had used initialy.

I just went out and drained the oil out of it. Of course milky.

I am about to drain the anti freeze now. I just want to make sure though first that its ok to leave it stored like this with no anti freeze in it?

I also was wondering on your diagram there it says step 2 to remove power steering cooling line? Is that somewhere I should be dumping water from?

I do not have power steering on this boat. there is only a hose on the front for the thermstat going into the exhst manifold.

Re: mercruiser 3.0 water in oil

I am about to drain the anti freeze now. I just want to make sure though first that its ok to leave it stored like this with no anti freeze in it?

Click to expand...

Ayuh,... Many of Us store our motors Dry,... Just Drained, No antifreeze...

I also was wondering on your diagram there it says step 2 to remove power steering cooling line? Is that somewhere I should be dumping water from?

I do not have power steering on this boat. there is only a hose on the front for the thermstat going into the exhst manifold.

Click to expand...

If you had P/S, it would have it's cooler in the line coming in from the transom to the t-stat housing...

You should also pull the Big hose off the circulating pump,... It tends to hold back some water...

Re: mercruiser 3.0 water in oil

Ok, I am new to this. I bought the boat to have a little fun working on it and rebuild it. I am smart enough to do anything that I have learned and figure things out, but I have not had a boat before so this is all a learning expierence for me. I do thank you for everyones help and advice on this because there realy is not any other way to learn but from others who have done it before. i dont have any reasonable mechanics in this area who do I/O except the merc dealer who is sporting 135/hr. shop rate and I wanted to work on it myself anyway.

I just drained out my AF today and started to try a block preasure test.
I would hope that I am doing this correctly but you guys tell me. I am a bit confused on the water flow direction here. It makes reasonable sense that the exhaust manifold would be a water return. I only have one 5/8" line that comes from the transom to the front and connects to the thermostat housing wich I am not too sure of this lise purpose?? Is it an inlet or out? I am guesing that the water is pumped in from the lower back side at the outdrive?

I removed the 5/8" line from the therm housing and pluged it.

I removed the line from the thermstat housing to the exhaust housing pluged it and used it as my air inlet and am pushing the air in toward the block, not the exhaust housing.

I am sure that I am missing something that I need to plug here because logic says that the water needs to go somewhere else.

I applied about 15lbs of air and it is holding it. there are no audible leaks. I have kept the preasure on currenlt to see if the preasure drops slowly, and it seams to be holding it.

Because I am not sure if I am realy getting it right, I went ahead and opened a drain on the lower block to see if air was there, and it was.

I took out each spark plug one at a time to see if any air came out and none did, preasure still there.

removed the oil cap on the valve cover, no air. removed the oil drain plug, no air.

Ok, what part am I doing wrong? and what else should I try?

Re: mercruiser 3.0 water in oil

Because I am not sure if I am realy getting it right, I went ahead and opened a drain on the lower block to see if air was there, and it was.

I took out each spark plug one at a time to see if any air came out and none did, preasure still there.

removed the oil cap on the valve cover, no air. removed the oil drain plug, no air.

Ok, what part am I doing wrong? and what else should I try?

Click to expand...

Ayuh,.... Good News,.. That says the block Ain't cracked....

How over Full was the oil this time when you drined it,..??

Re: mercruiser 3.0 water in oil

It seemed like about four quarts in the pan. I have not ran it since the first time before winterizing.

Dos it sound like I had it preasurized right? I was not sure because I didnt remove anything else or plug anything besides what I listed before. i was kinda figuring that there was something I needed to plug up somewhere else.

should I go ahead and refill the oil in it for over the winter, or leave it drained?