How to destroy a new $20K diesel

[Valmika]

Hey A64, Wouldn't the engine only fill with the fresh water if it wasn't running. If it was running you should see it ejected I would think

[a64pilot]

Originally Posted by Mark Killam

Hey A64, Wouldn't the engine only fill with the fresh water if it wasn't running. If it was running you should see it ejected I would think

Yes, exactly, if it were running, it would not fill with water I wouldn't think

[hellosailor]

"Water exits heat exchanger up through the anti siphon and comes back down to the exhaust elbow"


A heat exchanger would imply a separate cooling system, a "fresh water" closed cycle cooling system, wouldn't it? Not a raw water system, where the seawater is usually just pumped through the block and any transmission cooler?

[a64pilot]

Yeah, I am assuming a 4 yr old 20K engine is fresh water cooled, although you can water lock either can't you?
What I am doing is questioning if they waterlocked the engine in the flush proscess, like maybe shut it down, then climbed out of the boat and walked over to shut the hose off or similar.
Other than an outboard I've never owned a raw water cooled engine.

[a64pilot]

If the OP can't find a reason for this damage, I'd be suspicious is all, not that you could prove it, nor I'm sure they would not accept responsibility, so this is all theoritical?

[Scout 30]

Exactly the point of my question. If you hook a hose up to the raw water side without the engine running it will fill the engine up with water.

[Terra Nova]

The exhaust hose out of the water-lift muffler appears to have been routed improperly. That hose should be run directly UP from the muffler to the highest point in the system, then pitched DOWN to the outlet. NOT run across the entire engine room before going up. That created a huge volume of water to back-flow into the exhaust manifold, and past the exhaust valves.

[jongleur]

...exhaust hose out of the water-lift muffler appears to have been routed improperly...

That was my first thought also. Is that water lock
accumulator big enough and low enough for that
length of wet exhaust?

[DeepFrz]

You don't say why the engine needed replacing in the first place. Had it water locked by chance?

Anyway, my guess is that when they replaced the engine the raw water hoses were not replaced nor cleaned. I would check the anti siphon valve at the top of the vertical hoses to see if it is clogged. In order for that much salt to accumulate it had to be accumulating for a period of time I would think. Before starting the engine I would replace those hoses from the heat exchanger to the injection elbow and service or replace the anti siphon valve.

The point of the exhaust hose running horizontally across the engine room is a valid point. I don't know how you would address that other than move the water lift muffler to the aft end of the engine. You would end up with it higher which is also not a great thing but it might be the answer to a problem.

Is the heat exchanger separate from the exhaust manifold or is it part of the same casting. If it is part of the same casting then check to make sure it isn't cracked and leaking salt water into the exhaust manifold.

Flushing the engine should never be done with a hose. The raw water pump inlet hose should be inserted into a bucket of water with the hose keeping the bucket filled only. Then the pump will draw water from the bucket.

I hope this is helpful.

[Terra Nova]

Originally Posted by DeepFrz

...The point of the exhaust hose running horizontally across the engine room is a valid point. I don't know how you would address that...

It must rise from the muffler to the highest point in the exhaust system BEFORE going aft.

[a64pilot]

If that's the exhaust hose from waterlock, that makes no sense at all, why would anyone run the hose back around the front of the engine like that?
Take a whole bunch of water to fill the muffler and all the hose back up past the exhaust elbow, but maybe?
This thing ran for two years though before the problem?

Appears it first runs from the port side of the engine across the back, then around the starboard side of the engine, then across the front then back down the port side?

[Terra Nova]

Originally Posted by a64pilot

...This thing ran for two years though before the problem?...

It could have taken 2 years before the problem manifested itself as a destroyed engine.

[a64pilot]

Originally Posted by Terra Nova

It could have taken 2 years before the problem manifested itself as a destroyed engine.

Seems it did, I can't understand why anyone would run the exhaust like that

[Old Swampy]

Another possibility is that the engine is too far below the top of the exhaust hose resulting to excessive water in the hose when the engine is shut down. This water running back into the muffler might back up to the manifold. However, my guess is that the salt caked in the manifold during you normal usage. The salt, being hydroscopic, might expand to complete the blockage. However, burning the carbon out by running the engine fast before shutting down each day would only affect carbon in the exhaust portion of the manifold, not the cooling water portion.

[Scout 30]

This is a fresh water cooled motor. You can see a radiator cap on the heat exchanger. The only place on this motor that salt water mixes with the exhaust is at the mixing elbow which is after the exhaust manifold & typically higher than the block on Yanmars. After the mixing elbow the water & exhaust should go directly to the muffler. If the engine is running water cannot back flow into the engine. There may be a siphon loop that is higher than the mixing elbow but no other part of the exhaust line should be. The small amount of water in the siphon loop would not back into the motor & the water from the exhaust line, being lower than the mixing elbow would not back into the motor when it is shut down. If water backed into the motor from the exhaust line whenever it was run it wouldn't have lasted a week. If there is water in the engine it's because it was flushed improperly or the starter was run for a long time without the motor running. When water backs into the engine from the exhaust it enters the pistons & you cannot turn the motor over because the water will not compress.