smugglers blues

Hey everyone, I have twin 454s in my 84 Scarab. Stock exhaust, with 3 inch spacers raw water cooled. After 2 engine failures to leaky exhaust (took me 2 times in row to learn the hard way) I am now replacing all the exhaust components. I have become a little gunshy of these systems and am going over it all with a fine tooth comb. I am confused about this whole restrictor gasket vs. open gaskets on the risers and manifolds. Can someone tell me whats the best way to go here and why? I saw the recent bulletin from Mercruiser on the issue but it appears to me its referring to gen V motors and I am Gen IV. Any advice on this? Would be very much appreciated.

mr3dman

The restrictor that goes on top of the 3" riser on both sides is there to help equalize the water pressure between the port and stbd manifolds.. People have run without the restrictors and been ok, I have as well. The only negative on not running the restrictors is that you will probably have a higher temp difference between the risers. The one thing you don't want to do is run one side with a restrictor and the other side without. If you want to keep it factory, run the open gasket on the manifold to spacer joint and the restrictor gasket on the spacer to riser joint. Don't use sierra or paper style gaskets. Use the merc/ quicksilver gaskets..

smugglers blues

Thank you mr3dman for the quick response. That makes sense to me. Does it matter which direction the restrictor ports are installed? Do the small restrictor holes face the starboard/port sides of the manifold or bow/stern. Or does it not really matter?

f_inscreenname

I would think the gasket is longer one way then the other and should only go on one way.

smugglers blues

f inscreenname, no I think you are referring to the "log style" manifolds and risers. Mine are perfectly square "center rise" exhuast.

mr3dman

f inscreen is correct in saying that you will find that they are just a tad longer on one side. You will find that out when you install them, same part number for all the iron exhaust from your motor till the 496 came.. Anyway, I believe they will line up with the restrictor holes forward and aft if I remember correctly.

smugglers blues

Thanks guys, I am gonna go with the restrictior gaskets. Now I just need to decide if I am buying new elbows now. While the manifolds and spacers looked like they just came off the titanic, the elbows look brand new. I just realized they are stainless merc elbows. I was kind of excited thinking I may not have to buy elbows but after some research...people don't have much good to say about stainless elbows. Complaints that heat across the stainless/iron joints expands at different rates creating gasket failure. Anyone have any experience or knowledge about this? New iron elbows the way to go?

f_inscreenname

The stainless merc risers are the way to go. Cast is only used when there is nothing else you can use.

smugglers blues

f inscreenname, so you think I should keep the ones I have? I think they are 10 years old. They look great though, I don't see any corrosion but the age of these things scares me.

blue thunder

The 3 inch spacers are no good. They raise the height of the riser significantly causing you to have to use longer riser studs. It is nearly impossible to keep these from leaking if you run in any sort of rough water. I recommend you look at imco SS tube elbows that fit the center rise manifolds. I lost 2 engines as well before I switched to these risers. Well worth the cost they are....