I'm replacing the exhaust on my BB 502. I have a set of IMCO Powerflow risers/pipes with the round exhaust hole in the flange. I have to purchase a set of powerflow risers to go with the pipes. I have seen that there are two types of powerflow manifolds, the recirc and the standard ones. I would prefer to use the recirc ones because I could plumb the manifold and the riser together and the water would not have to pass through the flange. I'm concerned with the cooling water passing through the flange leaking and possibly causing reversion. Do IMCO's have gasket leaking problems or are they pretty solid with regards to not leaking? Like I said, I prefer to use the recirc manifolds but when I called IMCO to check on the availablity of them, I was told that they no longer make the recirc maniolds with the round exhaust port. Has anybody else heard this? I kind of felt like the guy at IMCO was giving me the runaround.

It's true, they don't make the re-circ model with the round port .... they don't make any of the Powerflow model with the round port ... the new manifolds are/were called the Powerflow 2000 and they now have an oval port. A new set of re-circ Powerflow manifolds would be nice

A friend of mine has a new set of Imco Powerflows that he put on his 540 this season. The gasket between the riser and manifold leaked on 1 side. Not enough to do any real damage, but still it was a problem. Personally, I like manifolds with by-pass hoses like Gils'.

YB,
Just finished my third season with Imco Powerflows .
Mine are round and have the internal water passage. Had them apart a few times (for other reasons) and replaced the gasket with a new one each time , plus a thin coating of silicone , no problems. This is mostly fresh water and flushed if in salt water .