4.3L Water Circulation Diagram

[zealer]

Hi, I have a Mercruiser 4.3L V6 #0M676089

Does anyone have a diagram of the water circulation? I am getting water in the oil. The boat was winterized and I haven't even run it long enough yet to have circulated the anti-freeze out of the block. Does anyone have a diagram of the water circulation route? I'm trying to determine where the water could be coming from before I start tear down. Since the thermostat hasn't opened yet (right, since the anti-freeze hasn't been dumped out yet) I am guessing perhaps it is leaking somewhere in the top end like from the heads or intake manifold. Thoughts?
Thanks

 

[Scott06]

Hi, I have a Mercruiser 4.3L V6 #0M676089

Does anyone have a diagram of the water circulation? I am getting water in the oil. The boat was winterized and I haven't even run it long enough yet to have circulated the anti-freeze out of the block. Does anyone have a diagram of the water circulation route? I'm trying to determine where the water could be coming from before I start tear down. Since the thermostat hasn't opened yet (right, since the anti-freeze hasn't been dumped out yet) I am guessing perhaps it is leaking somewhere in the top end like from the heads or intake manifold. Thoughts?
Thanks

Did you drain the block before circulating antifreeze? i also believe the vortec 4.3 has a drain plug in intake cross over that needs to be taken out.

dont have a cooling digram but the water supply hose to thermostat housing usually comes up from the drive on top of intake. If you plug the inlet and the 2 or 4 hoses going to the exhaust you can pressure test the cooling system.

 

[nola mike]

Did you drain the block before circulating antifreeze? i also believe the vortec 4.3 has a drain plug in intake cross over that needs to be taken out.

dont have a cooling digram but the water supply hose to thermostat housing usually comes up from the drive on top of intake. If you plug the inlet and the 2 or 4 hoses going to the exhaust you can pressure test the cooling system.

There is a plug in the head, but Merc doesn't mention it in the winterization procedure. I've pulled it a couple of times after draining the rest of the block and the cavity has been dry. There's also a lot of space in there/room for expansion. I've left it in through quite a few hard freezes. Anyway, couldn't find which manual ops serial number needed. Here's a pic of the post '93s... But yeah did you drain the block first?

 

[zealer]

Thank you for the replies. I bought the boat already winterized. It was done professionally but 2 seasons ago. Guy I bought it from said he couldn’t get it started last spring, got busy with other stuff and just left it in storage. I bought it under the assumption the engine would need to be replaced. Previous owner, As part of his troubleshooting he had pulled all the plugs out and then left it like that for a year. Once in my driveway, I got it started very easily. There is probably more to the story.

The block is still full of antifreeze, as is the intake (pulled the plug at the front of it and antifreeze poured out).

Trying to figure out (and hopefully get lucky) that the water in the oil is from run off and not a crack somewhere. I would have thought I’d see evidence of the antifreeze in the oil, as it is colored. Just a guess.

Anyway, I will pressure test next.

 

[Scott06]

Thank you for the replies. I bought the boat already winterized. It was done professionally but 2 seasons ago. Guy I bought it from said he couldn’t get it started last spring, got busy with other stuff and just left it in storage. I bought it under the assumption the engine would need to be replaced. Previous owner, As part of his troubleshooting he had pulled all the plugs out and then left it like that for a year. Once in my driveway, I got it started very easily. There is probably more to the story.

The block is still full of antifreeze, as is the intake (pulled the plug at the front of it and antifreeze poured out).

Trying to figure out (and hopefully get lucky) that the water in the oil is from run off and not a crack somewhere. I would have thought I’d see evidence of the antifreeze in the oil, as it is colored. Just a guess.

Anyway, I will pressure test next.

You may have 4 lines going from thermostat housing to the exhaust manifolds and elbows vs what is shown in the schematic mike attached. The 4.3 originally in my boat has a serial number close to yours had that.

No big deal just plug all 4 to isolate the block heads and intake for pressure test.

You can also get water in through cracked exhaust manifolds. Wonder if the PO had it properly winterized, hooked up the flush hose to start and introduced water to engine displacing some AF? If the PO pulled all the plugs there wouldnt be AF in block still....

 

[zealer]

You may have 4 lines going from thermostat housing to the exhaust manifolds and elbows vs what is shown in the schematic mike attached. The 4.3 originally in my boat has a serial number close to yours had that.

No big deal just plug all 4 to isolate the block heads and intake for pressure test.

You can also get water in through cracked exhaust manifolds. Wonder if the PO had it properly winterized, hooked up the flush hose to start and introduced water to engine displacing some AF? If the PO pulled all the plugs there wouldnt be AF in block still....

Sorry I meant the spark plugs. Pulling the spark plugs was part of his diagnostic to see why it wouldn't start, and then he left the spark plugs out for over a year while the boat sat.

And yes the thought did occur to me that while PO was trying to start it, he left water in the manifolds. Unfortunately I only thought of this after I started it myself and found water in the oil, and by then it was too late to check if water was left in the manifolds because I had obviously just pumped some there myself.

I'll start with the leak down test of the block, and then if that checks out move onto the manifolds. I have changed the oil once already and just with running the engine for 2 minutes on the fresh oil I got pretty good contamination.

 

[Scott06]

Sorry I meant the spark plugs. Pulling the spark plugs was part of his diagnostic to see why it wouldn't start, and then he left the spark plugs out for over a year while the boat sat.

And yes the thought did occur to me that while PO was trying to start it, he left water in the manifolds. Unfortunately I only thought of this after I started it myself and found water in the oil, and by then it was too late to check if water was left in the manifolds because I had obviously just pumped some there myself.

I'll start with the leak down test of the block, and then if that checks out move onto the manifolds. I have changed the oil once already and just with running the engine for 2 minutes on the fresh oil I got pretty good contamination.

Even if u are not getting more water in you will need to change it several times to get all the contamination out. You can change only 3 qts or so then change.

You have a good plan see what the pressure test tells you. If it holds he may have just gotten water in via condensation.