340 monsoon engine replacement

[Bluefishcay]

Bought a response last summer with a 340 monsoon.  Block was cracked due to water freezing and then repaired with jb weld.   Am now replacing the engine with a new long block.  While doing so I found water in the exhaust on almost all the cylinders.  Maybe 1/2 tsp per cylinder sitting on the top of the valve.  Is this normal for a wet exhaust?  Manifolds leaking?, if so how do I verify as it’s a big expense to replace them.  Cracked head?  Condensate from freeze/ thaw cycles?   Stored in an unheated building.  

[csleaver]

To check the exhaust manifold for leaks, remove it, connect a hose to one of the water fittings, block off the other fittings, and turn on the faucet to the hose.  Look for water coming out of the manifold ports were it connected to the cylinder head.

Here is a video to give you a basic idea of how to do it.

 

 

[Bluefishcay]

Checked both manifolds and no leaks.  Perplexed on where the water came from.  Maybe condensation as it was cold when I pulled the boat.  Also not a lot of water on each valve.  Just enough to pool and cause rust. 

[Rack]

Take a sample of the oil and have it analyzed. cost about 40 dollars

Its like a blood test for your engine.

[BuFootin]

I had a Response Lxi with the 340 Monsoon and would get a slight condensation buildup up In cylinders after running in cold water then letting it sit in an in-heated building.  Found it by chance after I pulled a few spark plugs and noticed they had water droplets on them.  Immediately panicked ….but never any water in the oil and it ran fine for years.

[Bluefishcay]

6 hours ago, BuFootin said:

I had a Response Lxi with the 340 Monsoon and would get a slight condensation buildup up In cylinders after running in cold water then letting it sit in an in-heated building.  Found it by chance after I pulled a few spark plugs and noticed they had water droplets on them.  Immediately panicked ….but never any water in the oil and it ran fine for years.

I wonder if this is what happened.  I ran water to the manifolds with no leaks, yet all 8 cylinders had a small amount of water sitting on the valves when I removed the manifold.  It was cold when I pulled the boat, water temp 40’s and air temp the same.  I suspect this may be common, but people simply don’t pull manifolds all that often, thus don’t see it. 

[BuFootin]

You say “ small amount of water”….if guessing is that a teaspoon or a quarter cup?  If it’s closer to a teaspoon I’d say “ no problem”

[Bluefishcay]

Small amount, maybe a teaspoon.  Enough that it was rusty.  Could be just condensation, just never ran into anything like that before. Have pics, but don’t have a way to host to post them.  

[Malibumastermechanic1]

Replace the manifolds , pressure testing does not work. They can have thermal cracks that open only when they get warm. 
seen it at least a dozen times 

[Steve B.]

Think I'd warm it up gently watching and listening and smelling like a hawk. Shut off frequently. Maybe remove the suspecting manifold while it's good and warm and look for water. Quadruple check the oil. Then let her cool down completely for a period of time, and look for the condensation again.

Steve B.

[Bluefishcay]

There was no water in the oil.  Manifolds did not leak when water was put to them.  I expect that since it was in every cylinder, and I pulled the boat in sub 40 deg water temps, it was probably condensation.  

[Steve B.]

Ah. Every cylinder definitely points in that direction. I'm also wondering if the condensation issue isn't magnified by that exhaust design and alloy. Where similar iron exhaust systems may not react the same. Hope it runs great from here on.

Steve B. 

[Bluefishcay]

On 1/27/2023 at 10:36 PM, Steve B. said:

Ah. Every cylinder definitely points in that direction. I'm also wondering if the condensation issue isn't magnified by that exhaust design and alloy. Where similar iron exhaust systems may not react the same. Hope it runs great from here on.

Steve B. 

Let’s hope so.   New engine is in and was test fired in the shop.  Will be a few months until it’s back in the water.  May just pull a manifold to check for water as they are easy to remove and no gaskets.