Brand New Merc 3.0 Riser Arrived With Rough Finish, Are they all like this now?

[PeterB26]

HI,

Time to do risers and manifolds on my 3.0L Mercruiser. I bought OEM kits for both the manifold and the riser. They arrived Friday afternoon. Upon unpacking the brand new factory OEM riser elbow the outer surface finish on the riser elbow is VERY rough. A coarse sand-like texture left from the casting process. This is a concern where the large rubber exhaust tube has to make a good seal against this really crappy finish. The old one was pretty darn smooth thereabouts... as it should be. My first reaction is to send this riser back as defective. It sure looks sub-standard to me.... but thought before doing so I'd ask if anyone else has seen this issue.

It's ugly.

It's bad.

It doesn't look to me like it is going to make a good seal at all.

Are all coming in like this? Has Merc dropped their standards this low?
Maybe OEM isn't the hot way to go on this item... anyone have feedback on other suppliers?

or I'd have to improve the finish with an epoxy filler coat or something... sure to fail with heat cycles and time....
or to make it seal I would have to glop it up with a load of perma-gasket or the like, which is SO NOT my style. I strive to do my mechanical work precisely, properly, neatly, and do it well, not slap it together with "caulk and glue."

BTW I was also surprised to see the sealing gasket surfaces painted over on the riser/manifold joint on both the riser and the manifold. That's gotta go! But I can live with cleaning up a little paint especially if painting it meant the surfaces didn't corrode on the shelf. Still it is poor practice for critical sealing surfaces.

Thanks,
Peter

 

[JoLin]

I just replaced mani's and risers on one of my 4.3's and yes, all the sealing surfaces were painted over. They also tend to be not entirely ready for 'mating'. It's normal. I took a flat file to them and carefully filed in all directions until nearly all the paint was gone, then finished up with a wire wheel chucked in my drill. The outer finish was pretty smooth but certainly nowhere near a mirror finish. I had no qualms about sliding the exhaust hoses over the riser ends, and there were no issues afterward.

 

[NHGuy]

I like the paint on the seal surfaces. They're not head gaskets. And they're not exhaust manifold gaskets either. They use graphite coated steel gaskets that only need 25 foot lbs to seal. They run at maybe 120 or 140 degrees, and carry a very small amount of pressure. I think the coating will prolong the service life of the parts.
Talk me into filing them next time they are apart, I will listen.
As far as the outlets, if they are too coarse I'd complain. I have some near new OE risers in my shop and they aren't like that.

 

[PeterB26]

Thanks for the feedback.

Yes, the mating surfaces do need some more prep than just paint removal before mating. Not impressed for the $ I paid, but it is easy enough to do.

I did some searches on the 'net to see what I could find for photos of similar risers to check thier surface finishes. It is hard to be sure becuase most are just stock photos, but the finish on many of them are rough like mine, while some are smooth like the originals..... so I suppose the rough finish, as much as I don't like it, isn't considered a defect.