Overheated due to bad impeller, now have water going into #3 cylinder and milky oil

[samocamo123]

Hi, I have a 1986 Ebbtide Montego 170 with a 3.0l stringer 400 (302sthrcom) and I overheated my boat due to an impeller failure and had to limp it back to the dock in short trips before it would overheat again. I replaced the impeller as it was in pieces and was going to go back out on the lake, but it ran rough when I tested it on muffs. I noticed the #3 cylinder had milky colored water going into it and the exhaust manifold cap now has water spraying out of it. The oil was clear but after trouble shooting (for only about 5 min, not including limping it back to the dock after overheating), it looked milky. What could be wrong? Could it just be a blown head gasket or is it something else?

 

[Scott Danforth]

Pressure test to verify, however head may be warped and head gasket toast

 

[samocamo123]

Pressure test to verify, however head may be warped and head gasket toast

Can the head gasket be blown without the head warping? Also, if its possible, how likely would it be? I believe both the head and block are cast iron.

 

[Scott Danforth]

when I got my 3.0, the head was warped from a prior over-heat. it took 0.015 to get it true. anytime the head gasket goes, you need to check the flatness of the head and the block deck with a ground straight-edge and a feeler gauge

heads warp all the time from over-heat events.

 

[southkogs]

When I did the head gasket on my old Stringer, to have the heads done was just a couple hundred bucks. The head looked amazing ... especially compared to the rest of the engine

 

[Lou C]

With a bad overheat, warping heads is likely and they can crack as well. This was the case with my 4.3, the block deck was fine, not warped but the heads were both cracked in the exhaust valve seat of the center cyls. So I would up installing a set of re-man heads. This is why you should always have heads checked by a machine shop.

 

[Lightwin 3]

Can the head gasket be blown without the head warping? Also, if its possible, how likely would it be? I believe both the head and block are cast iron.

Block and head are cast iron

Check the head and block with a straight edge as mentioned.

Also, look in your thermostat housing for more impeller pieces. I found a bunch in my 4.3 housing.

 

[Lou C]

You can check for flatness with a mechanic's straight edge and feeler gauges. Most engine specs call for no more than .003", but it really should be less than that.
However, you can't see cracks that may be in a cyl head, that will show up with magnafluxing that a machine shop can test for.

 

[samocamo123]

As an update, I have tested compression and got 90 80 30 110 with the engine cold. I also took the head off and it wasnt visibly warped (I couldnt see a gap when I held a straight piece of metal up to it as I dont have a good straight edge yet.) The head gasket didnt have any obvious blow outs, but it was just a sheet of thin metal (none or little rubber anywhere on it.)

 

[southkogs]

If you've got it all apart, I would just have it machined and cleaned up. You definitely have something going on with those compression numbers.

 

[Lou C]

Make sure they check it for cracks. That water came from somewhere. Post a pic of your head gasket, head and block deck.

 

[samocamo123]

If you've got it all apart, I would just have it machined and cleaned up. You definitely have something going on with those compression numbers.

Make sure they check it for cracks. That water came from somewhere. Post a pic of your head gasket, head and block deck.

I will post pictures tomorrow, do you have any idea on what it would cost to have the heads checked and or machined? I would like to spend as little money as possible as its a pretty old boat (if possible I would like to just replace the head gasket and go to the lake before it warms up too much for good fishing.)

 

[Lou C]

My machine shop charged $40 or so to check them, they found that they had cracks and the cooling passages were eroded to the point where it made more sense to buy re-man heads so that's what I did...

 

[samocamo123]

I will post pictures tomorrow, do you have any idea on what it would cost to have the heads checked and or machined? I would like to spend as little money as possible as its a pretty old boat (if possible I would like to just replace the head gasket and go to the lake before it warms up too much for good fishing.)

I finally checked with a straight edge today, and in the worst spot it was 0.013" warped. I would imagine this means it needs milled? Also does any one know how to mill a warped head? (I have access to a cnc mill, but dont have any special tools for head work so I would like to know if it could be done with standard mill tools) I attached pictures of the block deck, head and head gasket. The head has been cleaned but the rest are untouched.

 

[Lou C]

I think I see a crack on the valve seat area on cyl #3. You need a good machinist to look at it for you at this point. Also is there pitting in the cyl wall of #3?

 

[samocamo123]

After having the head worked on, I installed it with a new head gasket and manifold gasket and (with engine hot) I got roughly 105-115 in all 4 cylinders. Is this compression good enough or does this mean I will need a rebuild eventually?

 

[Bondo]

I got roughly 105-115 in all 4 cylinders. Is this compression good enough or does this mean I will need a rebuild eventually?

Ayuh,..... Should be 150 psi,.... It's already pretty much worn out,.....

 

[samocamo123]

Ayuh,..... Should be 150 psi,.... It's already pretty much worn out,.....

Hmm, my boat only has around 600 hours on the engine. How could the rings be so wore?

 

[Bondo]

From over-heatin',..??..........

 

[Lou C]

I had a similar problem and even with the blown HGs, my comp test results were close to normal. After I replaced the heads with reman heads and new HGs, my comp test results were 160-175 or so...