Hairline fracture on exhaust manifold and riser?

[boataway]

what are the risks to running with hairline cracks in the manifold and riser (VP 5.7 GX-i)?

I noticed some rust spots on the outside and upon closer inspection, both seem to have cracks about 2 inches long. I've only had the boat for one year and not only did I drain and flush the engine block last fall, but I left the drain plugs out and use an engine bay heater. I'm guessing it was like this when I bought it, but since she was kept on a lift, there was no seepage to leave a rust mark.

There is no milkiness to the engine oil.

I'll try to post a picture soon...

 

[tpenfield]

The risk would be if there is also an internal crack that can have water collecting around the valves.

 

[boataway]

No Title

wouldn't I see the oil turn that milky color?

here's a picture.

 

[tpenfield]

wouldn't I see the oil turn that milky color?

Not necessarily . . . Depends. But that is the risk that you asked about

 

[evantful]

It wouldn't be wise at all to continue running with them like that. It certainly does look like two cracks. If it did that externally it could have done that internally also.
Its not great having to spend the money now, but having to replace the manifolds/risers now is a lot better than having to replace the manifolds/risers AND a Long Block later.

 

[Maclin]

Water from the exhaust manifolds/risers could only get into the oil through the piston rings and even then not much before a hydrolock would occur. Water would only get into the top of the engine, I.E. heads and cylinders, if the manifolds have internal cracks. There are two passages inside them one for exhaust gases and one for cooling water. The cooling water gets mixed with the exhaust in the riser and expelled in the exhaust stream. If there are cracks internally that let the water leak into the exhaust ports when the engine is off then damage will occur.

 

[boataway]

does the boat need to be out of the water to replace those two items?

 

[evantful]

It can be done in water if need be. The only thing you would want to do it in a calm area, or to plug the exhaust hoses temporarily when you disconnect them from the risers to prevent backwash from waves pushing into the transom (it really wouldn't be likely but better to cover all your bases).

 

[BRICH1260]

Take them apart and inspect the inner linings. If not cracked, you might be able to buy some time until the end of the season when you can replace both of them. But assuming you can quickly get the parts, while they are apart, I would just replace now.

 

[boataway]

I'll order the parts to replace. Is there any reason why I couldn't just replace one side at a time?