Probable cause of water in cylinders on mercruseser 260 V8

[jerryb1]

Hi Guys,
I have 94 searay 260 Mercruiser GM engine and I/O drive. I'm trying to find out the most probable cause for at least 3 cylinders getting water inside. Heres the history- The engine has about 300 hrs. It ran fine on a 45 minute trip. I then stopped and anchored. When I tried to start it 10 minutes later it was locked up and I had to get towed back. I took the plugs out and the two middle cylinders on the starboard side and one or two on the port side spit water when cranked. What is most likely the cause- risers, a head gasket leak, cracked head, block etc.? There was no overheating on the trip.
I'm about to take it apart, but I was curious what you experts think happened.
Thanks

 

[Bondo]

Re: Probable cause of water in cylinders on mercruseser 260 V8

Ayuh,... The manifolds are the 1st suspect...

 

[ENSIGN]

Re: Probable cause of water in cylinders on mercruseser 260 V8

sounds about right,pressure test them and the engine so you don't have to guess

 

[Pete104]

Re: Probable cause of water in cylinders on mercruseser 260 V8

Manifolds? possible but check the water shutters too!

 

[lcmains1]

Re: Probable cause of water in cylinders on mercruseser 260 V8

Could be a numberof different things. There is a troubleshooting guide for water in the cylinders on here and should also be one in your manual

 

[TilliamWe]

Re: Probable cause of water in cylinders on mercruseser 260 V8

Ayuh,... The manifolds are the 1st suspect...

Yep, always the first thing to check. Suspect #2 is the risers, suspect #3 is the exhaust shutter (flappers), suspect #4 is the manifolds again, #5 is the risers again Then maybe #6 is head gaskets/intake cracked. Water in a marine engine is usually and exhaust iddue of some sort. Please don't go pulling heads until you are sure about the exhaust, then the intake.

 

[jerryb1]

Re: Probable cause of water in cylinders on mercruseser 260 V8

I finally got around to working on this boat. I get 120lbs cylinder pressure on about half of the cylinders, the remaining cylinders i only get about 60 lbs pressure. I am able to start the engine and run it for 20-30 seconds at a time without water. My thinking is I should at least rebuild or replace the heads?

 

[jerryb1]

Re: Probable cause of water in cylinders on mercruseser 260 V8

Also forgot to mention, there was water in 2 cylinders on each side, so if it was a manifold problem, I doubt if they would both fail at the same time? No?

 

[Doernuth]

Re: Probable cause of water in cylinders on mercruseser 260 V8

Is there water in the oil? Pull the dipstick and see if it looks like a milkshake.

Were the wet cylinders the ones that you have been getting water out of?

 

[dubs283]

Re: Probable cause of water in cylinders on mercruseser 260 V8

Also forgot to mention, there was water in 2 cylinders on each side, so if it was a manifold problem, I doubt if they would both fail at the same time? No?

which two cylinders on either side have water intrusion??

its possible to have both manifolds fail, but not likely, more likely is failed water shutters or riser gaskets - due to undetected overheat

it sounds as if you skipped checking the manifolds and went right to a compression test??

running the engine without water and the drive still on (sterndrive) or belt on the sea water pump (inboard) will fry the water pump in no time

 

[Bamaman1]

Re: Probable cause of water in cylinders on mercruseser 260 V8

In New Jersey, I would think the engine is a victim of freezing.

Anyway it goes, you'll need to disassemble the motor. Just take it step by step. The problem will surface as you get into the disassembly.

Pulling an I/O engine is really not that difficult.

 

[jerryb1]

Re: Probable cause of water in cylinders on mercruseser 260 V8

The two middle cylinders on both sides shot water out when cranking. These are the cylinders that I only now get 60 lbs compression. I see some rust on the valve stems when looking into the exhaust ports. I think I should buy new heads as they only cost about $400 a piece, and with 60 lbs pressure in 4 cylinders, i dont know what else to do. I still don't know how the water got in? Everyone seems to suggest it was an exhaust manifold, flaps, or riser problem, but can someone explain how it would happen on both sides the same day at the same time?
Also, I didn't see any water in the oil, at least I couldn't tell from the dip stick.
I pulled off the intake manifold yesterday and I don't see any obvious problems there?
if I replase the two heads, is there a way to pressure test the block? If the block was the problem, will i see it when I remove the heads?

 

[John_S]

Re: Probable cause of water in cylinders on mercruseser 260 V8

The heads are probably the symptom, not the cause. Sounds like you have it pretty much torn down. How about some pictures of both ends of the risers and exhaust manifolds?

 

[Stamey]

Re: Probable cause of water in cylinders on mercruseser 260 V8

I agree with the above. You need to methodically check the various components, using your current observations as clues. Just because the valves look rusty does not mean that there is a head problem. Those valves could rust from condensation in the heads over the winter.
You are looking for a crack in a manifold, exhaust elbow or riser, failed gasket, or the exhaust flappers for your water intrusion. As for your low compression, you are looking for a failed head gasket as the likely culprit, but depending on how quickly the water got in there, and how hot the engine was when the water got in those cylinders, you could have broken rings, as they are very brittle and a sudden flood of water in a cylinder can break them. I know this from my days of 4-wheeling in some pretty deep water.

The others here are offering valid, knowledgeable advice, and you'd be wise to take the methodical steps they recommend unless you just feel like throwing money at it.

Chris

 

[John_S]

Re: Probable cause of water in cylinders on mercruseser 260 V8

As far as likelyhood of both sides leaking, if these are the original manifolds, and boat has seen salt or brackish water, I'd say highly likely. One side probably would start before the other, but you can go a while before enough water is draining back and causing an issue. On center risers, the middle cylinders would see the most water from a leak. If they were not drained properly, they could both be cracked.

On the heads, you could test if it was rings, valves, or both. Common for the vaves to rust along with seats, preventing a good seal. If they had been leaking for a while, then there is also higher probabability of cylinder rust, and scouring, especially if saltwater sat in there.

 

[jerryb1]

Re: Probable cause of water in cylinders on mercruseser 260 V8

Thanks Guys- I appreciate every bit of information. The manifolds and risers were only about 2-3 years old. I bought the boat beginning of last summer, so I dont know exactly when they were changed but they didnt look that corroded. I did notice some rust at the interface to the manifold,riser and elbows at the outside. There was no sealing compound on the gasket between them.( I thought there should have been some)
I agree that the rust could have been from condensation over the winter as I left the starboard side manifold off and the plugs out all winter( I probably should not have done that).
Bottom line is I now only have 60 lbs pressure in 3-4 cylinders. I'm pretty sure it's from the rust on the valves/seats, as i squirt oil into the plug hole and the compreesion still shows low, so It's probably not a ring problem.
As I said previous the engine started okay, and I know about frying the impeller, but i didnt run it that long, so hopefully not.
I dont mind changing both heads, putting new manifolds and risers as I own this boat with a buddy, so the cost would at least be cut in half. The engine has 560 hrs on it and it's 15 years old. My only concern is that the block is bad and we dont want to change all this stuff and find it still has a problem. That is why I asked if I pull the heads off will I see any issues with the block, and can I test the water passages for leaks?

 

[jerryb1]

Re: Probable cause of water in cylinders on mercruseser 260 V8

A couple more questions. I can buy new vortec heads for $395. a piece. Is it better to do that or bring my heads to an automotive machine shop and have them rebuilt? Are there compatibility issues with new heads?

 

[FreeBeeTony]

Re: Probable cause of water in cylinders on mercruseser 260 V8

If I were you I would get a Vortec longblock from Rapido......the heads you are talking about are already $800.

Just my $0.02...........and you would have a "new" engine........thats what I did about 4 yrs ago.
It would suck if you replaced the heads only to find you have problems down below...

 

[Stamey]

Re: Probable cause of water in cylinders on mercruseser 260 V8

It's a can of worms. An automotive machine shop may be able to pressure test the block, but you should call around and ask before you go pulling anything. You may be able to pressure test the entire engine assembly, if you can obtain the necessary parts to block off everything, mainly hose inlets and outlets going to manifolds or coming in from the outdrive.

Typically, if it's big enough to leak that much compression, you'll be able to see the crack in the block as soon as you pull then heads. I bought an '83 chaparral, with a 305", last year that needed a head gasket. I pulled the heads, and with no prior knowledge of the boat, any why the head gasket blew, I sent the heads to a machine shop to have them checked for warpage. They found no significant warpage, but did find the valve guides bad. I ended up resurfacing, new valve guides and valve job, 300 bucks later. Still cheaper than one of the heads you were talking about buying.

What I found out, after re-assembling the engine, was that the manifolds and exhaust elbows were corroded enough on the inside that they were restricting water flow to the point that the engine was overheating. This was key information that the PO didn't supply, or didn't realize. It is worth noting that the elbows I removed did not look corroded, from what I can see in them, so I had no hint by looking at them when I had the engine apart.

Once I put the new elbows on the overheating problem has now been minimized, in that any speed above idle the engine runs fine, but sitting at idle for 10-15 minutes will get it pretty warm.

If it were me, I'd pull the heads first, and see what I can see. Clean up the block surfaces and see if there are any obvious cracks, and maybe have the machine shop check the heads out, before I did anything else. If the block and heads check out OK, as far as cracks, I'd then see what the cost would be to make the heads right, including guides and whatever else. If I liked the price I'd go with the rebuild of the existing heads. If the head(s) are cracked, we need to ask why, and decide what direction is best to go now.

If I had known the reason for the blown head gasket when I bought my boat I would have passed on it, but I was already in 400 bucks worth, not including labor, before I know what caused the head gasket to blow. Fortunately I found elbows for steal, and then manifolds over the winter for a reasonable price.

Chris

 

[jerryb1]

Re: Probable cause of water in cylinders on mercruseser 260 V8

Thanks again guys. I spoke to a local machine shop and he said he will test the heads if I bring them in. He would rework them for $175 , but suggested new for $375, as he said since it's salt water cooled the passgaes would probably be corroded. FreeBeeTony mentioned to buy a new Vortec block if I was changing the heads and basically have a new engine. Two concerns with that are one, the reviews on that company sound like a nightmare, and second I would then have to pull the drive which seems like a lot more work. I replaced a lower unit on my old alpha, but never removed an upper. How difficult is that?