Saltwater Intrusion into Diesel Engine

[Honeyman]

Aside from the exhaust riser not being high enough, what are other conditions under which saltwater can get into your engine? Can it happen while its running? Mechanic on a friend's boat said it had suffered saltwater intrusion while running hard, healed over. John Deere diesel. Any thoughts?

 

[Ross]

Busted gaskets and seals.

 

[Ed Schenck]

Which gaskets and seals Ross? Something in the waterpump and/or heat exchanger?

 

[RichH]

1. Broken seal on water pump ..... high pressure water gets pumped into crankcase
2. Pinhole in exhaust manifold ..... when engine is shut down (and both valves are closed on a cylinder - causing vacuum; water can migrate through the pinhole into the combustion chamber and leak down into the crankcase (plus starts the cylinder walls and pistons rings to 'rust').
3. Broken head gasket. Water is drawn into the combustion chamber on the downstroke of the piston though the broken head gasket ... is removed by 'steam' if the engine is still running; but, will be free water when the engine is stopped (similar to #2)
You may see 'carbon' in the freshwater side of the cooling system OR if you add the correct chemicals will cause a special dye to fluoresce (glow) when the water is contaminated with carbon monoxide (plus excess of CO2 when viewed under 'blacklight'.
4. cracked engine block or cracked cylinder head ---- see all of the above.

 

[Mike Turner]

Second RichH on his first point - on the boat we just bought, there was a LOT of water in the crankcase oil; turned out the raw water pump seal had burst on the run from the owner's dock to the yard to be hauled for the survey. Rebuilt pump with new seal solved the problem.

 

[Glenn17467]

I had a blocked heat exchanger and rusted over raw water pump drain holes caused salt water to back up through the pump shaft into the crank case. A cracked head should allow water from the fresh water system (coolant) unless the engine is cooled by raw water.

 

[Ed Schenck]

Seems to me that most of Rich's points are for coolant water, not salt water. On three of the diesels that I have owned only the new 3YM30 uses an "internal" pump for saltwater. So the heat exchanger, I think, would be the only source of salt water on the other two(QM's). They both had external belt-driven pumps for sea water.

 

[Bill Roosa]

Running hard???

If he was heeled over he was under sail not motoring. So he probably had salt water enter the exhaust which you already know about.
Salt water can come from 2 places; the exhaust outlet at the back of the boat and the thru hull raw water intake.
Other than the exhaust the most common way salt water can get into the engine is to crank it without it starting. The raw water pump fills the exhaust up to the manifold and it then enters the engine.

 

[Ross]

Re: Running hard???

Funny that I see mention of flooding the exhaust lines when cranking. My engine starts blowing water out with every turn before it starts.

 

[Chuckbear]

Funny that I see mention of flooding the exhaust lines when cranking. My engine starts blowing water out with every turn before it starts.

That does not mean it is not taking in more water than it is blowing out.

 

[AXEL]

I use to get salt water in the engine all the time while under sail (heeling) unitll I figured out the problem was a clogged anti-siphon valve. I've seen this on other boats as well. It's always a good idea to have an anti-siphon valve coming from the exhaust riser and run up as high as possible. also check them, in my case the little breather hole became clogged.

 

[Honeyman]

This boat was healed way over motorsailing into heavy seas and 21-27kts of wind! Thanks for your ideas...