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5.7 getting water in cylinders

J

JFS13

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I have a 97 5.7 mercruiser EFI. I went to start boat today and engine was locked up. Removed spark plugs and had water in cylinders 7&8. I winterized last year. Ran antifreeze and then drained block and exhaust manifolds. I don’t understand where water came from if I drained everything.
 
Tell us more about what lead up to this

Was it running fine and then it had water, or is this first start of the season?
Cylinders 7&8 being on opposite sides, are you in salt water or fresh?
 
First start of season. Shouldn’t be any water in block and manifolds. I drained them when I winterized last year. I think it’s rain water getting in carb. Little salt water mostly fresh water.
 
I use to not think so but that’s why Merc, Volvo and OMC started using those plastic covers over the carb. Thought it was for show but it makes sense. Just for winter storage you could use a large freezer bag over the flame arrestor.
 
JFS13 said:
First start of season. Shouldn’t be any water in block and manifolds. I drained them when I winterized last year. I think it’s rain water getting in carb. Little salt water mostly fresh water.
Click to expand...
Even though you drained it, water still could have gotten into the rear cyls if your elbow gaskets leaked, like right when you shut off the engine. Do you see rust trails around the joint between the manifold & elbows? A 97 is still the wet joint exhaust, correct?
I started using an endoscope camera to actually look inside the exhaust elbows to see what the joint looks like inside. I just remove a casting plug and the camera shows what the inside looks like.
 
Last edited:
exhaust staboard side.jpg

Here's an example of the pix I can get. So you can check at the beginning or end of each season without having to take it all apart.
If it's leaking there will be rust trails around the joint and rust pooling in the bottom of the manifold.

Sometimes when your exhaust is running cool (like running at idle speed or on the water hose in the driveway) you'll see little bits of corrosion, this isn't a leak but is evidence of condensation from a cool running exhaust:
exhaust port side.jpg

this is the port side, it always runs cooler than the starboard side, on my old 4.3 OMC Cobra.
 
This is an OMC/Volvo style system but Merc is similar, you just have to find a pipe plug in the elbow that is willing to come out (lol) and the camera and its snake will fit right in. I used the ones on the top of the elbows that are actually for an optional exhaust system temp sensor.

4.3 with new exhaust system.png
 
louc said:
I use to not think so but that’s why Merc, Volvo and OMC started using those plastic covers over the carb. Thought it was for show but it makes sense. Just for winter storage you could use a large freezer bag over the flame arrestor.
Click to expand...
Okay thanks
 
louc said:
Even though you drained it, water still could have gotten into the rear cyls if your elbow gaskets leaked, like right when you shut off the engine. Do you see rust trails around the joint between the manifold & elbows? A 97 is still the wet joint exhaust, correct?
I started using an endoscope camera to actually look inside the exhaust elbows to see what the joint looks like inside. I just remove a casting plug and the camera shows what the inside looks like.
Click to expand...
I removed the exhaust elbows last year to look how manifolds and risers looked. They looked good and I replaced gaskets.
 
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