They are aluminum and they worked out great so far.I have those manifolds for sale,I just installed a set of CMI today and had CMI weld in the bung when I ordered them.

Nordic95

That looks like a good location and clean job. I have the EMI exhaust with long stainless risers. I had bungs installed at the factory. They placed them in the same location as yours. I use Holley MPI kit and I can monitor the O2 on my laptop. I am thinking about getting a O2 gauge to mount on my dash since I have a open port.

I emailed Dana Marine and for $195 they'll put O2 bungs on both risers. Looks like I only need one though. They said they'd have to weld them further downstream where they could weld from the inside too. I'm worried about water on the sensor if it's that far downstream

I realize that this is a really old post but I'm curious if your having trouble keeping O2 sensors alive? I have a similar adapter in mine and have lost 2 O2 sensors.
Do you have any suggestions? Thanks

I believe the Innovate Motorsports Bung Extender would extend the life of your O2 Sensors. It's what I use.In cold water the condensation on the inside of the pipe can kill O2's or any amount of reversion will definitely do it as well

Thanks for the suggestion. I've heard good things about those extenders, particularly for protection from heat. I'll give it a try, I just need to figure out how to install it an angle so the water doesn't collect on the sensor.

Get your post count up to ten and upload some pictures. There is a wealth of knowledge available here.