Water in oil...

[Drew3521]

Well I’ve got a 1991 Caravelle Classic 1750 with an I/O OMC cobra and I’ve got water mixing with the oil. I’ve replaced riser and had manifold checked, no water on plugs boat runs great. Except for the oil being extremely contaminated with water added almost a quart in 25 minutes on the water. After changing the oil I ran it on the muffs for about 15 minutes and no contamination run the boat in the river and it’s filling the crankcase. Any ideas? All cylinders are at 150psi for compression test. Boat has always been properly winterized and the freeze plugs haven’t moved. Also replaced water flapper in exhaust. Any help would be great. Thanks.

 

[kenny nunez]

Unfortunately, you have a cracked block. The crack is probably under the intake manifold. You did not say what engine you have and I am just assuming it is a Chevrolet. If there is no crack then there is a pin hole leak somewhere.

 

[Drew3521]

Unfortunately, you have a cracked block. The crack is probably under the intake manifold. You did not say what engine you have and I am just assuming it is a Chevrolet. If there is no crack then there is a pin hole leak somewhere.

3.0 gm just took the head off gasket looked good piston heads didn’t look washed nice carbon on them. I’m gonna say cracked block internally?

 

[Drew3521]

3.0 gm just took the head off gasket looked good piston heads didn’t look washed nice carbon on them. I’m gonna say cracked block internally?

No cracks that I can see so it’s gotta be internal

 

[Scott Danforth]

many times the 3.0 block cracks on the inside just above the pan rail

 

[kenny nunez]

The thinnest part of the casting is usually at the bottom of the water jacket Inside of the crankcase. You might be able to get a fitted block which comes with main ,cam bearings & pistons with rings. You re use every thing else. Otherwise just get a marine short block. Marine Power in Pontchoula,La. would be one place to look. Be careful with used engines.

 

[Drew3521]

The thinnest part of the casting is usually at the bottom of the water jacket Inside of the crankcase. You might be able to get a fitted block which comes with main ,cam bearings & pistons with rings. You re use every thing else. Otherwise just get a marine short block. Marine Power in Pontchoula,La. would be one place to look. Be careful with used engines.

Thanks man. Yeah looking at just getting a whole new 3.0 well reman the head doesn’t look all that great. Either might as well replace it and forget it. Instead of fighting with it every time I take the boat out.

 

[hugh g]

Well I’ve got a 1991 Caravelle Classic 1750 with an I/O OMC cobra and I’ve got water mixing with the oil. I’ve replaced riser and had manifold checked, no water on plugs boat runs great. Except for the oil being extremely contaminated with water added almost a quart in 25 minutes on the water. After changing the oil I ran it on the muffs for about 15 minutes and no contamination run the boat in the river and it’s filling the crankcase. Any ideas? All cylinders are at 150psi for compression test. Boat has always been properly winterized and the freeze plugs haven’t moved. Also replaced water flapper in exhaust. Any help would be great. Thanks.

I had the same exact issue on my own 3.0 a few years back. Turned out to be a bad exhaust manifold. I changed that & the riser & never had an issue after that. Btw, the guy who pressure tested the manifold said it was ok. Oops! And I changed the head gasket & had the head planed which solved nothing.

 

[Drew3521]

I had the same exact issue on my own 3.0 a few years back. Turned out to be a bad exhaust manifold. I changed that & the riser & never had an issue after that. Btw, the guy who pressure tested the manifold said it was ok. Oops! And I changed the head gasket & had the head planed which solved nothing.

Problem I’m having is they don’t sell my manifold anymore can’t find a new one anywhere. Did your pistons look washed when you pulled your head I pulled mine today and they don’t look like waters been getting to the top of pistons here’s a picture of what the pistons look like. None of the valves look clean either. I heard when waters getting in from manifolds/risers top of pistons will look almost steam cleaned. Any ideas?

 

[hugh g]

Problem I’m having is they don’t sell my manifold anymore can’t find a new one anywhere. Did your pistons look washed when you pulled your head I pulled mine today and they don’t look like waters been getting to the top of pistons here’s a picture of what the pistons look like. None of the valves look clean either. I heard when waters getting in from manifolds/risers top of pistons will look almost steam cleaned. Any ideas?

I don't quite remember what the pistons looked like as it was more then 15 years ago, but I do remember finding water on top of #4. I lucked out & had no engine damage & ran the boat right up to 3 years ago. When I had the issue I ran the engine off muffs & thought I was in the clear after changing the head gasket. I launched it & after running for 5 minutes that sucker was full of water again.

 

[Jrobbs3]

Problem I’m having is they don’t sell my manifold anymore can’t find a new one anywhere. Did your pistons look washed when you pulled your head I pulled mine today and they don’t look like waters been getting to the top of pistons here’s a picture of what the pistons look like. None of the valves look clean either. I heard when waters getting in from manifolds/risers top of pistons will look almost steam cleaned. Any ideas?

Regarding your manifold sourcing issue. I ran into the same problem with my OMC 235 recently, replacement stock manifolds are obsolete. I was able to find a source after quite a bit of looking. Check: https://bpi.ebasicpower.com/shop/. I'm not sure your engine specifics but looks like they have a couple of OMC 3.0L options.