We had a rather disappointing end to our 2010 season when water started filling our bilge on our last outing. The best I can determine is that the Y-Pipe for the exhaust has rusted through and some of the seawater cooling the exhaust is going into the bilge rather than going overboard.
Does anyone know if the Y-Pipe can be changed without pulling the engine? Budds'Outlet is a 1990 Sea Ray 270 with a single 7.4L mated to a Bravo 3 outdrive.
1999 Sea Ray 330DA
Twin 7.4 MPI (310 propshaft HP) V-drives
All standard equipment including:
Twin Mercury Marine marinized 7.4L L-29 V8s
Cast iron block w 4-bolt mains
4.25x4.00 bore & strok
Re: Mercruiser Y-Pipe
I had the Y-pipe out of my previous boat, which had a stern-drive. There was nothing wrong with the Y-pipe, but the oil pan was leaking, so I pulled the engine to change the pan. While I was in there, pulled everything else, including the Y-pipe that would make it easier to clean the bilge.
You must pull the engine, which isn't that bad if you have access to a hoist. Secondly, the Y-pipe and the inner transom plate are aluminum. They won't rust. But it can corrode. The seal is a formed rubber gasket that's like an O-ring. If the Y-pipe is loose, it might leak. More likely than the Y-pipe is that your drive bellows or shift bellows are leaking which will drip water onto the Y-pipe making the pipe look like the suspect. Check carefully after cleaning everything as well as you can. Then inspect with a mirror and a light to ensure that water isn't coming from above.
Thanks for the responses guys. That's good advice on making sure I knowwhere the leak is before taking things apart. That I will do.
I am pretty sure that it is exhaust related below the waterline as it made a "burbling" sound and the sound changed with engine speed. The sound was inboard, inside the engine compartment. Nothing sounded different outside the boat. Just the normal bubling of the exhaust. Also, the Y Pipe is also the only exhaust component that is not fairly recent.
I will of course be very certain that I have identified the leaking component before I take anything apart. The gasket between the plate and the Y Pipe is an interesting suspect although I'm not inclined to think it would lose its seal and start leaking without some provocation. I'm also not inclined to think it would be the drive bellows as a leak in the drive bellows would not be accompanied with an exhaust related burbling sound.
Lots of theory going on in my mind without solid facts. I'll need to do some crawling around with a mirror and light to get better information.
Thanks for the info Frank. I think I'll inlist the aid of my friendly boat mechanic on this if I can't readily detect the hole. Without the back presure from the seawater I doubt I can replicate the problem with muffs on the drive while the boat is up on the trailer. Considering the situation I'm also not likely to relaunch the boat until this is cured. You are probably right, its going to be hard to see the problem area.