Exhaust y-pipe leak

b_arrington

b_arrington

Well-Known Member
GOLD Sponsor
Feb 21, 2007
3,485
Setauket, NY
Boat Info
Back Cove 37
AB Ventus 9VL
Engines
Cummins QSC 8.3 600
The 98 270 DA I help maintain had leak into the bilge that I discovered. The boat was hauled yesterday and the engine pulled out based on the symptoms. The mechanic said the exhaust y pipe is badly corroded, and it looks like it’s from electrolysis.

With the understanding that I don’t know how the y pipe connects, it seems weird that that part would be attacked. Any thoughts on why it might be that case? The zincs on the B3 drive typically wear normally.

Other info. The boat is slipped and connected to shore power. Batteries are always off when docked. My boat is 2 slips over and seems to be OK with normal zinc wear. I replaced a dead battery charger and batteries this spring.
 
Mine rotted away at the bottom, it was a tight fit in the keyhole and collected trash was keeping it wet
It's an aluminum pipe connected with 4 stainless screws
 
scoflaw said:
Mine rotted away at the bottom, it was a tight fit in the keyhole and collected trash was keeping it wet
It's an aluminum pipe connected with 4 stainless screws
Click to expand...
When I replaced the motor and transom in my 270 I found the ears on the bottom of the y-pipe were basically gone. They look like they had corroded as well. I’m not sure exactly what caused it. However I replaced it when I did the motor.
And - same conditions - salt water, batteries always off at end of the day - verified mercathode worked with tool..
 
If you are plugged in to shore power make sure your galvonic isolator is functional too. Otherwise your boat is grounded to every other boat on the pier and has become the anode for all the other boats.
 
We had the engine out 2 years ago to replace the leaking transom plate. I think the y-pipe was replaced at they time, but the mechanic a checking the maintenance records.

If it was, it would be a really fast deterioration.
 
Hoplite808 said:
If you are plugged in to shore power make sure your galvonic isolator is functional too. Otherwise your boat is grounded to every other boat on the pier and has become the anode for all the other boats.
Click to expand...

I’m not sure there is a galvanic isolator on the boat. I don’t recall seeing one when I was working in the engine room replacing other stuff.
 
b_arrington said:
I’m not sure there is a galvanic isolator on the boat. I don’t recall seeing one when I was working in the engine room replacing other stuff.
Click to expand...
It would be with the AC wiring. The one on my ‘96 270 is behind the AC breaker panel.
 
This is from my manual - I don't ever remember looking for it but apparently its there somewhere :)
upload_2022-7-14_16-42-44.png
 
I spoke to the mechanic today and he showed me the y-pipe. It was new 2-ish years ago when the transom assembly was replaced.

It looked to be in great shape - except one of the four mounting ears was completely corroded away. That made the pipe loose and allowed in the water. Suspect is some type of electrolysis as discussed. He’s going to reassemble with some type of anti corrosion compound, and I’ll have to find and check the galvanic isolator.
 
The area where the pipe mounted to the hull was pretty corroded too, so I can see why it was leaking.

I'm not tackling this repair - the mechanic has 50 years of experience so I'm going to let him do the work.
 
Ouch - I remember that pipe isn’t cheap either :(
 
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