4-53 DDs with rusted airboxs & blowers but no apparent leak???

A question for the Detroit Diesel experts.

I have two 4-53's in the same boat with similar damage. Both engines will hold pressure on the fresh water cooling system for 24hrs. Neither engine shows oil in the water or water in the oil. Both engines have valve train that looks to have at max 50 hrs run time if even that. All injectors from both engines have not a spot of rust on their tips, so I assume the chambers are dry.

AND both engines have rusted out blowers and airboxes. The airboxes are currently dry, and mostly composed of red dust!

Short of an engine room flood that allowed water entry directly through the air intake what else could have caused the air boxes and blowers in both engines to rust out this way? If it was a flood, why no rust or water in the oil? I see no high water mark above the bilges.

I'll be pulling the heads next week. What should I be looking for as to a clues about the cause of this damage?

pictures are port and starboard engines. Rusty outside but not so bad as to hint to totally dusted blocks from the inside no?

 

No ideas? Anyone, Anyone, Anyone?

 

Salt water spray will do that.

 

Hi Gonzo,

Could water in the bilges, or general high humidity in the engine room cause this? How would a salt water spray have gotten into the airbox? Ingested through the blowers maybe?

Leo

 

Where are the engineroom vents located?

 

behind the motors. The blowers and intakes face the bow and are about four feet ahead of the vents, and maybe three feet up from the bilge.


+ what is weird is that both engines were this way. I could see one getting swamped or sprayed, but both?

 

At the speed the air is entering the engineroom at WOT the spray can easily go four feet. Ideally there should be some kind of water trap.

 

pull the airbox covers on the other side from the blower and have a look inside.

 

The blower can't rust out, it's aluminum.

 

Hi Powerabout. I did open the airbox. The cover itself fell apart in my hands. The inside is huge chunks of rust. Can;t even see the ports on the cylinders, they are somwhere under the rust. Both engines look the same.

Hi Slow Fred,
Rust is the wrong word. Think about lots and lots of white corrosion. It's so deep that you can not even see the rotors. It looks like someone just packed flower into the blowers input. I can kind of vaguely see where the rotors should be - and perhaps even discern thier shape.

 

Hi Gonzo,

I see a lot of boats just like mine with the blower intake just sitting there with nothing but the marine flapper valve. I was shocked to not even see an air cleaner. Perhaps the spray entered becuase the 4-53's have the blower intake on the hull side, where as the original 6-71's had them on the centerline of the boat? Could such a simple mistake during the repower have resulted in the destruction of two good engines? What evidence could I look for to confirm that this is what happened?

 

It depends on the boat type and use. If the boat was run at high RPMs on heavy seas where the vents were hit by waves, it can ingest lots of water.

 

when you pull the airbox covers and you see rust 99% chance that came through the inlet.
assuming the engine coolant is still full and it wasnt full with plain water?

Being able to assemble one engine opposite the other is a very cool feature of inline jimmys in a boat.

 

Hi Powerabout. I did open the airbox. The cover itself fell apart in my hands. The inside is huge chunks of rust. Can;t even see the ports on the cylinders, they are somwhere under the rust. Both engines look the same.


Sounds more like the boat sank (perhaps for a good while) and the engines were never serviced .

With that must rust it is doubtful the engines could be rebuilt as the block is probably shot.

Replace or repower would seen to be the only option.

 

If you buy a new detroit now do they come with a RR badge?