Sorry I did not get back to you from your pm sent to me. Your 5.0 came with the non dry joint exhaust manifold & riser set up !998 thru 2001 0L serial # run had a 7 degree riser. The riser gasket for standard cooling was restricted but if you had the riser ext kits then the riser gasket was open NON restricted gasket.

If you had any water reversion problems you could have installed riser extension blocks to raise the height of your exhaust set up to combat against it. (water reversion). This is common with pleasure boats that have the added on or heavy added length swim platforms and everyone hangs out back there while at rest in the water. That is a big cause of water reversion in the pleasure boats. FYI

The positive with dry joint exhaust manifolds & risers is exactly what is says a dry joint in between the manifold and riser mated together compared to your older style that was not. I take this is why you want the Dry joint set up boating in saltwater.

Just adding some other info on top of - There is no performance gain by converting over plus the dry joint manifolds & risers and riser gaskets is more expensive than your older set up. Of course the exhaust manifold gasket itself is the same. Matter of fact the dry joint riser gasket is a tad more restrictive for exhaust flow because it has a smaller opening. The tabulator design for the dry joint exhaust riser set up.

Also less aftermarkets have or sell the dry joint set up compared to the non older style exhaust set up. With the dry joint exhaust manifolds & riser set up, we see more exhaust manifolds gaskets blown than your older style exhaust set up. Couple of reasons, one Mercruiser when new had them torqued wrong (not enough) and the other reason is the dry joint manifold and riser is heavier and a lot heavier if you add riser extension blocks to it. We see that combo blow exhaust manifold gaskets all time. To help prevent it or at least to get longevity against blown exhaust manifold gaskets is keep checking your exhaust manifold bolts for proper torque settings. Good luck

Hey Bup, Thanks for the info on checking the torque frequently. I did the dry joint install this wknd and so far so good. My manifolds are osco , 3 inch spacers are Barr and the risers are HGE. Thats the only way I was able to get a complete set. When I removed the old set, The down turn elbows, which connect the risers to the y pipe, were 2 totally different parts. After Iinstalled the new dry joint setup, neither would fit or have the correct angle to the Y Pipe. Just out of luck, I found this place in Sarasota Florida. http://www.marinesurplusinc.com/servlet/StoreFront. It was about an hour from me and they listed some down turns on their site that looked like they might work. I took my old ones to compare and find a better angle and length. This place probably had 15 different down turns in stock, brand new and CHEAP. 50 a piece. Merc wants 189-289 each... After looking at 8 or 9 different castings, I found a set I thought would work. Brought them home and they fit perfect. Next time I am at the boat I will look at the casting #. We also Installed a remote oil filter kit. It attaches to the riser. WARNING. Don't use the washers for the riser bolts if you use a kit like this. Or use longer riser bolts. Dont ask...lol.. All is good now.

Chris

If the mating surface on the manifold and riser is still in good shape.Go for the gasket that has the two long holes and the 2 little round holes.Reason is the one with the four large slots tend to make the water eat away at the machined surfaces and you get a leak at that point.The one with the two little round holes lets the air in the top of the manifolds escape and tends to slow down the turbulence at that joint around the riser,has been my experience any way.Been putting them back like that since center rise manifolds came out works fine.Regardless what was on there.DO Not use a bunch of silicone sealer if at all.That is how I would do it.My 2 cents