3.0L Mercruiser Alpha One Water in Oil

[kaeden1100]

Hey guys!

So I'm fairly new to boating (Been around boats for 2-3 years but just got my first boat this year.) I've got a 1992 Bayliner Capri 1700 with a 3.0L Mercruiser Alpha One. I've had no problems from the boat up until about a month ago. I was checking the oil before I went out and noticed water in the oil. The oil was very milky, resembled chocolate milk quite a bit. So I was naturally very alarmed. I immediately changed the oil and filter. Then after talking to a few friends they suggested it was probably a head gasket. So I checked the compression on all 4 cylinders and compression was good all the way around. It's also worth noting the boat never overheats. It really never even comes close. It sits pretty solid at 140 no matter what. So after checking compression and it looking okay, I was confused. I checked around for obvious cracks or leaks and couldn't find anything. So I decided to take it back out. I've had it out about 3 or 4 times since then and I checked the oil before and after going out everytime. It looked clean. Up until the 4th. We were out all day on the 4th and I checked it before we went out but forgot to check it after. I went to go out again this weekend, checked the oil, and sure enough it was milky again. So I'm at a loss here. All my local marine shops are 3+ weeks out right now, so just trying to see if it's anything I can figure out so that I'm not basically done for the season waiting on a marine shop.

Again, this is my first boat. I'm a mechanic so I work on cars for a living, but boat motors are kind of a whole new animal to me, so any and all help is greatly appreciated!

Thank you!

 

[achris]

It started making chocolate milk after coming out of winter, yes?

Do you live in an area that freezes over winter? If so, exactly how do you winterize the engine?

Chris...

 

[Rick Stephens]

Not much difference twixt a boat motor and an automotive motor. Wrenching is wrenching.

There's a good post in the stickies about water in oil.
https://forums.iboats.com/forum/eng...s-outdrives/379100-water-in-your-oil?t=369864

Sounds like a cracked manifold since it didn't immediately put water in your oil after you changed the oil and used the boat a couple times.

Like Chris asked: you live where it gets cold in the winter?

 

[kaeden1100]

It started making chocolate milk after coming out of winter, yes?

Do you live in an area that freezes over winter? If so, exactly how do you winterize the engine?

Chris...

I bought the boat at the end of May, and the guy I got it from had just had it out the weekend before I bought it, I believe for the first time this season. Before he took it out though, he supposedly had just had the motor oil and gear oil for the outdrive changed. As far as winterizing I'm not sure how he did it to be honest. I imagine he had one of our local marine shops do it since he took it to them for all the other service. As far as it freezing in winter, yes. I live in Southern Indiana and sometimes (while rare), we will see sub zero temperatures. Not often and not very low below zero, however definitely below freezing for a decent part of the winter.

 

[kaeden1100]

Not much difference twixt a boat motor and an automotive motor. Wrenching is wrenching.

There's a good post in the stickies about water in oil.
https://forums.iboats.com/forum/eng...s-outdrives/379100-water-in-your-oil?t=369864

Sounds like a cracked manifold since it didn't immediately put water in your oil after you changed the oil and used the boat a couple times.

Like Chris asked: you live where it gets cold in the winter?

Okay, forgive me for my ignorance on this, but I know on a vehicle you've got an intake manifold and an exhaust manifold. It was my impression that on these 3.0 Merc's, Intake and Exhaust manifold are the same housing correct?

 

[Grub54891]

Okay, forgive me for my ignorance on this, but I know on a vehicle you've got an intake manifold and an exhaust manifold. It was my impression that on these 3.0 Merc's, Intake and Exhaust manifold are the same housing correct?

Yes.

 

[achris]

And the exhaust manifold in a boat is (usually) water jacketed. If the water isn't drained from the manifold properly, and it freezes... She cracks.

You can test the manifold in-situ. Remove the exhaust elbow (at the end of the manifold) and make and install a block-off plate. Set up a fitting on the front end (where the water goes in) and pressure it up. If the pressure drops, you have a leak. You don't need high pressure, around 0.7bar will be plenty to find a problem.

drain the water out before pressuring it up.

Chris....

 

[kaeden1100]

And the exhaust manifold in a boat is (usually) water jacketed. If the water isn't drained from the manifold properly, and it freezes... She cracks.

You can test the manifold in-situ. Remove the exhaust elbow (at the end of the manifold) and make and install a block-off plate. Set up a fitting on the front end (where the water goes in) and pressure it up. If the pressure drops, you have a leak. You don't need high pressure, around 0.7bar will be plenty to find a problem.

drain the water out before pressuring it up.

Chris....

Thank you for the information. Just to clarify, when you say drain the water first, you're referring to draining the water from the block correct?

 

[achris]

Thank you for the information. Just to clarify, when you say drain the water first, you're referring to draining the water from the block correct?

No, from the manifold...

 

[kaeden1100]

No, from the manifold...

Ah okay, my bad. So I assume there are drain plugs on the manifold itself then.

 

[achris]

Ah okay, my bad. So I assume there are drain plugs on the manifold itself then.

 

[kaeden1100]

Okay, thank you. And sorry again for the ignorance. Just don't have the boat in front of me and want to try and get as much information as I can before I go and take a stab at it. So I have an idea on where the drain plug is now. As far as removing the elbow goes, it should unbolt from the general area I outlined in the attached picture right? And then you're saying I need to come up with something I can block that off with something correct? And then as far as "Set up a fitting on the front end (where the water goes in)" you're referring to the opposite end of the manifold right, where I assume the manifold is fed through the thermostat housing?

Again sorry. I feel like an idiot here, I'm just trying to make sure I understand everything properly and don't mess anything up.

 

[kaeden1100]

Forgot to attach the picture.. my bad.

 

[achris]

Okay, thank you. And sorry again for the ignorance. Just don't have the boat in front of me and want to try and get as much information as I can before I go and take a stab at it. So I have an idea on where the drain plug is now. As far as removing the elbow goes, it should unbolt from the general area I outlined in the attached picture right? And then you're saying I need to come up with something I can block that off with something correct? And then as far as "Set up a fitting on the front end (where the water goes in)" you're referring to the opposite end of the manifold right, where I assume the manifold is fed through the thermostat housing?

Again sorry. I feel like an idiot here, I'm just trying to make sure I understand everything properly and don't mess anything up.

All correct. And don't feel bad about not knowing. We all started at the beginning.

Chris.....

 

[Rick Stephens]

A piece of plywood drilled for the bolts, and a gasket. Rubber is best.

 

[kaeden1100]

Another question. I've been working all day and haven't had a chance to take a look at the boat yet, but would it be easier to just remove the manifold and inspect for cracks visually? I know I'd need a new gasket when it goes back on obviously, just wasn't sure if that'd be easier than having to mach something up to block it off, etc.

 

[kaeden1100]

Okay, so I got a little free time on lunch and decided to actually take a really good look at the motor on the boat. That's when I noticed some small rust water lines on the side of the block that looked like they were coming down from the manifold.I know I probably should've pressure tested the system first, but my curiosity and time limit today got the best of me so I decided to go ahead and yank the manifold off. The results are pictured. I'm thinking maybe the gasket was my issue? I'm sure some of the damage to the gasket was done when removing the manifold honestly, but I don't see that pulling the manifold off could've done all the damage to the gasket. The gasket looks pretty rough honestly. Maybe original? Anybody else thinking the same here or know of anything I should check next while I've got it off?

 

[Rick Stephens]

There is no water held in by the gasket. So no, it wasn't the gasket.

Run a wire brush on the block where all the rust is in the middle under the exhaust and intake ports. See if there's a crack there.

 

[Grub54891]

Yeah, it looks cracked where Rick says. Common place for them to Crack when not winterized correctly.

 

[achris]

That has a crack-like appearance.