Merc 350 Y-Pipe

[greg82255]

Hello,

I just bought a new boat with a 1986 Merc 350. I am thinking about doing some modifications to the exhaust and noticed that the Y-pipe isn't exactly what I expected. I have heard that from 1983-2002 the same Y-pipe was used in the merc small blocks, with oval-shaped ends. The ends on this one appear to be circular (there is an about 80 degree bend that goes from the 3" risers to the Y-pipe that appears to have 2 circular ends), but it is clearly not the same design as the pre-1983 Y-pipe (I also own a 1982 merc 305). Was there a different Y-pipe made in this year or am I just seeing things? I'd rather not pull the thing apart before I have to just to look at the shape. Thanks

 

[series60]

Re: Merc 350 Y-Pipe

There are several different styles. To be sure which one you have it's best to take it off and have a look at the bolt holes. My 1984 Mercruiser 305 uses this style where one bolt hole is offset to the side.

If you do take it off be sure to look for corrosion around the mating flange. Critical area for water leaks. The black line I have drawn on the mating surface shows where the O ring mates to keep water/exhaust out of the bilge. There is no way the O ring could seal this surface with all the corrosion on the edges of the Y pipe.

 

[Bondo]

Re: Merc 350 Y-Pipe

I have heard that from 1983-2002 the same Y-pipe was used in the merc small blocks, with oval-shaped ends.

Ayuh,... You heard Wrong...
There are atleast 2 bolt patterns, 'n a couple of pipe patterns...

 

[greg82255]

Re: Merc 350 Y-Pipe

There are atleast 2 bolt patterns, 'n a couple of pipe patterns...

Any idea which one was used on the 86 Merc 350?

 

[Don S]

Re: Merc 350 Y-Pipe

Just a quick count in the OEM parts program showed 5 different Y pipes from 83 to 97. There are 3 different numbers from 83 to 86. There are 2 different Y's for the 3" exhaust.
Here is a page from the parts program that shows the differences in them.
Check your elbow casting numbers to find the right one.

 

[greg82255]

Re: Merc 350 Y-Pipe

Thanks Don, that gave me just what I needed to know