Pacemaker Boat Owners Association

i have a mercruiser 350 and i am getting a chocolate shake after running the engine for about 5 minutes she runs nice but overheats and no coolant in the heat exchanger when i turned her off. does anyone know where i should start? i am thinking it is a blown head gasket but hop not.

Any good shop would magnaflux your heads/block for cracks before doing any work to them/it. Problem is, either way you are looking at a partial tear down at least until you find a leak. Until you find the leak, stop running it or you will be digging yourself deeper.

This is the way to go


http://cgi.ebay.com/ebaymotors/5-7L-350 ... iesQ5fGear

What do you mean "a chocolate shake"? Do you mean a water-oil mixture in the crank-case? Do you mean stuff coming out of the exhaust? Do you mean an oil-water mixture in the cooling system? I assume the latter, but before I start offering advice to anyone regarding engine problems, I would first like to hear a reasonably clear description of the problem.

weel i found out what is was water was leaking in to the block from the inake manifold gasket replaced it and bam she doesnt leak.

Do at least 2 oil and filter changes to get the old stuff out of there.

will do just waiting the get the hull done before i can run her in the bay

Looks like you found out how the water was getting in, but where did the water come from? Still sounds like you're missing something to me.

Cap't Bill - I'd guess it was coming from the cooling system. These SBCs have openings to the water jacket at the intake manifold mating face at both ends of the heads (small, squarish holes in the image posted by Mike above). I'm assuming the gasket had failed for whatever reason beneath one of these ports and the coolant was draining down into the crankcase via the lifter gallery.

It's not such a rare occurrence...I've seen it once or twice.

Kind regards,

JoeBobb

well i am running water for coolant until i work out the kninks in the motor and tranny is chaeper tha coolant and since i am in my front yard doing the work it just works better.

Untill you are 100% sure on the leak solution water is good as antifreeze in the oil will eat your bearings. Sounds like you have the answer in hand. You can always do a pressure check as well.

well I am back to square one I have found more water in the oil so I am going to tear the heads off and go thru them completely. First i am going to do a leak down check just to see if that is the problem first. Thanks again for the help.

here is another update i just finished clean and lapping the valves and heads. I have torn the head off and cleaned them up. I took apart the valves and lapped them and to ensure a excellent seat. I painted the heads and reinstalled the valves. Now i just have to install them and test the cooling system.

there was a video on utube it was a ford motor that was getting water in the oil it was through the heads there are 3 plugs in the heads that go to the water jackets i dont know if chevy has the plugs or not
steve

Another thing to look for is in the area under the intake manifold. GM 350's some times develop a crack there. The good news is that you can repair it with a bit of work with a die grinder and some JB Weld. A buddy of mine went through that with his street rod and never had a bit of trouble with it after the fix.

Have the heads Magnafluxed at a machine shop to check for cracks. You can NOT see some cracks and they will open up as the engine heats up. GM heads are known for cracking between the water passage's and the oil passage. The machine shop will also do a pressure check on the heads to rule out internal leaks. Lapping the valves and cleaning the heads does nothing for a coolant into the oil problem. Time and material is to expensive to do the job twice. John

J.F.D. Services
Marine Diesel Repair

Well guys its happened again water in the oil and the antifreeze is getting suck dry. I have replaced gaskets boiled riser and still the same thing oil and water are mixing together. I am just going to take it to the mechanic and let them fix it if there price is in range or I will just buy a fuel injected motor with center risers. Any thoughs on what I should do?

If you are going to replace the engine then it's just a matter of how much you want to spend. You can spend the big bucks and get one that is all ready to drop in and start or you can go with a reman and use your old parts on it. Did you check your exhaust manifolds for leaks? That was where my problems all started, a failed manifold. I did a rebuild which due to bad parts or a goof on my part did not work out. I then bit the bullit and bought a reman long block on line and used all my perifials. The reman cost me $1450- with $150- in shipping. And it had a warrenty for a year. None of which my rebuild had. And push come to shove after looking at the recipts, the reman was cheaper. As I said, it's a matter of how much you will want to spend.

I am always a bit cautious about turning my stuff over to a mechanic unless they have an excellent reputation and I trust them. You did not mention if your manifolds are raw or fresh water cooled. I am guessing they are freshwater. I would pressure check the system before you do any kind of tear down and look hard at the manifolds. I would also be concerned about the bearings as the antifreeze will damage them.

I have pressure tested the system before and I noticed it had a drop in pressure. I will do another pressure test tomorrow and give you an update.