Merc 3.0 Cracked Block but Manifold ok?

[Mike1004]

Hello,

I did a number of searches but am left with a couple of unanswered questions.


I bought a 2012 Bayliner 185 as a winter project, previous owner didn't winterize and cracked the block. I knew this going in and have ordered a new long block.

He also indicated the manifold was cracked, I'm not sure.

I have done 2 tests on the manifold...
1. (From the sticky post) Filled water jacket with acetone for about 30 minutes... The acetone appeared to drop about 1/16 to 1/8 of an inch in the water jacket ports but I know acetone vaporizes quickly. Is this expected?

2. Blocked exhaust and water jacket port. Layed on side and filled exhaust ports with water. Pressurized the water jacket to 20psi and no sign of bubbles. Put it up to about 40psi and still no sign of bubbles. The manifold looks in good shape, no obvious external cracks and no rust or corrosion. .y gut tells me it's fine, anything to suggest otherwise?

When I pulled the manifold I noticed one of the middle exhaust valves was all rusted and clearly water was in there but the manifold is absent of the same damage.

I don't want to put a bad manifold on if there is any doubt but a new o e is $800 and if this one is good, I would prefer to use it.

Thanks in advance for any input!

 

[Rick Stephens]

Make a block off plate and pressurize the water jacket of the manifold through the inlet pipe.

 

[Mike1004]

Make a block off plate and pressurize the water jacket of the manifold through the inlet pipe.

I tried that and filled the exhaust ports with water with the manifold on its side.. no sign of any bubbles.

Are you saying pressurize and see if it holds the pressure?

 

[Scott Danforth]

over a $300 manifold you want to chance the engine? buy a new manifold

 

[Mike1004]

over a $300 manifold you want to chance the engine? buy a new manifold

Unfortunately it's about $800 here in Canada. I have no issues replacing it, unless I can be confident this one is good.

 

[Scott06]

Unless you knew the manifold was drained and block wasn’t I wouldn’t mess with it.my neighbor was too lazy to winterize his boat u til after it froze, seems ok until he used it 3-4 times I think took a couple heat cycles to pen the crack

 

[Scott Danforth]

Unfortunately it's about $800 here in Canada. I have no issues replacing it, unless I can be confident this one is good.

so hop in a car, drive south, buy it in the US, buy a tee shirt, drive back north.

 

[Mike1004]

so hop in a car, drive south, buy it in the US, buy a tee shirt, drive back north.

During non Covid times I would. Unfortunately borders are closed and it's a 2 week quarantine upon return if you manage to get down there. I will likely wait and see if they open back up closer to spring.

 

[Mike1004]

Unless you knew the manifold was drained and block wasn’t I wouldn’t mess with it.my neighbor was too lazy to winterize his boat u til after it froze, seems ok until he used it 3-4 times I think took a couple heat cycles to pen the crack

This is exactly my concern. I'll likely grab a new one given the uncertainty.

 

[Rick Stephens]

Are you saying pressurize and see if it holds the pressure?

Yes. 15# pressure. Should hold indefinitely.

Not arguing with the consensus that replacing it is best. Just stating how you check the mani to see if cracked.