260 oil in water please help

Hello, I have a 1983 mercruiser 260 hp. The boat sat for 4 yrs and when I started it and let it run about 15 minutes I noticed water in the oil.I changed oil and filter, and got the same results. I changed the head gaskets and manifold gaskets , and got the same results. I then tore it back apart got the heads done and pressure checked , and replaced a cracked exhuast manifold, and got the same results.after each time I took the motor apart I noticed the number 6 cylinder was full to the top with water. The engine runs ,and sounds great, but when I pull the plug out of the # 6 cylinder it shoots water.I did not visually see a crack in that cylinder when it was apart. Any help , please \. Thanks.

Re: 260 oil in water please help

sounds like your engine is craked letting water enter the cylinder prob from not winterized

Re: 260 oil in water please help

Hey welcome to iboats,
Are you running it on muffs or in water?
if so do i dont know much about your engine but is it a closed cooling system or open?
also what are your compresion numbers in number 6 if there is a crack they should be off if im correct(some senior here will let me know if im on the right track with that)

Re: 260 oil in water please help

You could have a leak between the exhaust manifold and the water jacket. Is the exhaust manifold you changed on the same side that #6 is on? You could also have issues with the seals between the risers and the manifolds. They need to be sound and tight.
Check the manifolds and risers, maybe just change the rest of them because of the age of the exhaust, or you could leak test em with acetone. To do that you seal up one end of the water jacket and fill the other with the acetone. It will find a leak better than water because the molecules can fit through a smaller space.
Does your motor diesel when you shut it down? That can make it take a gulp of water back up the exhaust.
If #6 is on the side with the new exh. manifold my guess is the riser cracked on the inside allowing water into the exhaust path.
I'm not a professional boat guy, they will be along in a while and say whether I am pointing you int a good direction.

Re: 260 oil in water please help

Ryanlewis2010 said:

Hey welcome to iboats,
Are you running it on muffs or in water?
if so do i dont know much about your engine but is it a closed cooling system or open?
also what are your compresion numbers in number 6 if there is a crack they should be off if im correct(some senior here will let me know if im on the right track with that)

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Thanks for your responce. I am using the water muffs on my open cooling system, and I do not what the compression is on that cylinder. I am also thinking there is a fine hairline crack in that cylinder.

Re: 260 oil in water please help

The exhuast manifold was replaced on the same side as the #6. I also thought it could be in the riser or manifold, but now Im thinking if that was the case I would be getting water in all 4 cylinders on that side.

Re: 260 oil in water please help

after changing the oil and then running how much water is in the oil but the only good way to determine wherther or not its the cylinder is compression all should read very close to each other

Re: 260 oil in water please help

Chris Craft230 said:

Hello, I have a 1983 mercruiser 260 hp. The boat sat for 4 yrs and when I started it and let it run about 15 minutes I noticed water in the oil.I changed oil and filter, and got the same results. I changed the head gaskets and manifold gaskets , and got the same results. I then tore it back apart got the heads done and pressure checked , and replaced a cracked exhuast manifold, and got the same results.after each time I took the motor apart I noticed the number 6 cylinder was full to the top with water. The engine runs ,and sounds great, but when I pull the plug out of the # 6 cylinder it shoots water.I did not visually see a crack in that cylinder when it was apart. Any help , please \. Thanks.

Click to expand...

Ayuh,.... Welcome Aboard,...

How much water is it taking on,..??
How high does the dipstick level rise, how fast,..??

My 1st guess is, it's cracked in the base, 'n you won't see it, til it's upside-down, 'n the pan is off....

Re: 260 oil in water please help

I'm thinking you mare right. I can.t tell you a exact amount but I can say , when I turn the engine over I keep getting a small squrt out of the plug hole.Thanks everyone for your help, I think at this point I,m looking to find a good used engine. Thanks