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Discussion Starter · #1 ·
Have a 1978 Yanmar SB8 Where we initially had the head gasket blow out on a water jacket that filled the cylinder with water. We replaced the head gasket and it fired up nicely, but was smoking a lot. We had it running for a good 15 minutes and we purposely shut it down and it wouldn’t fire back up. We pulled the glow plug and an awful lot of water came out which made us think we could have blown the head gasket again, but I would’ve thought it would take a hell of a lot longer than that.

What we’re concerned about is that the one water jacket where the head gasket failed last time is pretty worn out and could be too far gone.

The other theory we have is that the thermostat valve could be stuck open letting water in from the mixing elbow on the exhaust side.

For anyone not familiar with these engines they’re salt/fresh water cooled and have a water mixing elbow that pushes the used water out the exhaust.

I’m happy to hear any theories from those with experience with this particular model, or any diesel in general.

Thanks I’m advance
 

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Emmalina
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163 Posts
You can,t just change a blown head gasket without testing the head and cylinder block with at least a straight edge ! Single cylinder engines like that can be skimmed with a grinding stone quite effectively. I presume its raw water cooled.
 

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Master Mariner
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9,322 Posts
Is this fresh or salt water?
 

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One of None
Hunter 34
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8,921 Posts
Is the mixing elbow clogged? 3-5 years many even sooner
 
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