Riser Gaskets. Restricted or unrestricted
 

I am changing out my Manifolds and Risers on a 5.0Mercruiser IO Alpha Drive. I see that most offer 2 gaskets plus a closed cooling block off plate. I am not in any way referring to the block off plate for closed cooling. Question is what is everyone using. The 4 slotted one that is unrestricted or the 2 slotted one with 2 small holes in the 2 other sides which makes it partially restricted. FWIW I boat in South florida. Another thought is switching to Dry joint Manifolds. They 2 offer a restricted and unrestricted gasket. Any info or thoughts are appreciated.

Chris

dry joint is totally restricted. hence the term dry joint. but it really makes little diff which you use.

Ayuh,.... It depends on the t-stat housin', 'n how yer motor is plumbed,...

Without knowin' more of what ya got, the Best tip I can offer is,...
If it's been runnin' Fine, when ya pull the old risers off, take note of which gaskets were used,..
Then use the same style gaskets goin' back together,...

Use the wrong ones, 'n you'll get over-heatin' or hot spots,..

Dry joint is not totally restricted. They just moved the water passages for and aft. You can still get 2 different gaskets for it . They look like oring seals and one style is open in the middle and the other just has a small hole in it.

Chris

Thats a great Idea Bondo.. Problem is its a used boat and someone had put a mix match of parts on it. Mercruiser/glm on one side and Sierra /HGE on the other side. The merc side had the restrictor style gasket and the sierra side had full open. IE 4 slots open. I bought the boat cheap and only expected to get 1 season out of the motor. We ran the piss out of it all last season. Even with 90 degree water temps here in the gulf in july, it never overheated. So I figured I would slap some new manifolds on it for safety and hit it again this season. Decided to go dry joint because I think this motor is in better condition than I thought when I bought it. So putting good risers and manifolds on it and will run it till it breaks.. Probably several seasons. As far as the plumbing, It has the style thermostat housing that directs water to the bottom of the manifolds. Then water exits out the Risers to the y pipe. No hoses are connected to the Risers like on some models.. Probably why it has held up so good.. Its Simple...lol...

Chris

Will be interesting to see answers on this as I am also curious.

On my 5.7's, I run a restricted gasket as I have hoses going to both the manifold and the risers. Figure they are both getting water pushed through them but no idea if this is correct. I would think with no hose going to the risers, you would want unrestricted gaskets since all the water has to flow through it. That is my guess! LOL.

Interested to see what the correct way is if I am wrong. And why. The problem with being an engineer, I always want to know the "why".

Thanks for posting this question.

Brian

Post your serial # of your engine and just to make sure you have closed cooling or am I wrong about that. Also depending if you have riser extension blocks. so do have them in between the riser and manifold. Also Dry joint manifold and riser set up is taller than the non older standard type exhaust manifold & riser. Again all OEM stock parts and set ups go off of serial # not year model. It does not matter what every else has because marine apps & parts can change mid year or when a Service or parts bulletin comes into effect.

80 % of this forum do not have stock OEM set ups nor a lot of them do not have stock OEM parts on their engines so a lot of OEM info goes out the window but in your case seems like you are completely stock.

Don't have the serial number handy but have looked up parts by it before and it was inaccurate at best. I do not have closed cooling so that makes it easier. As far as the Height difference, Merc made 2 versions of the dry joint system as do all the aftermarket company's. The earlier ones before 2005 were standard height and standard degree og angle which is about 7 degrees. Later ones were taller and 14 degrees. I am going with the 7 degree setup. I do have 3 inch riser extensions and have found them in dry joint as well. I should be within a 1/4 to 1/2 inch of stock height. Back to the gaskets. I have decided to use the restricted ones but not sure if I want to put them at the manifold/extension joint or the extension/riser joint. This is a link to the riser company instructions. http://www.hgemarine.com/techinfo/HG...stallation.pdf. It just does not explain its use with extensions.
These are the extensions..
http://bpi.ebasicpower.com/pc/BARMC2...uiser+864929A3

Chris

Hense the reason why I ask post for your serial # because without eyes and hands on your motor who in the world would know EXACTLY what you had plus the set up. I sure did'nt and I'm Mercruiser dealer for 25 years and running. All serial # breaks can have different parts and different set ups installed from the OEM plus a lot of aftermarketers do not have the serial # info correct anyways. Mercnet is how dealers look up stuff & info correctly especially for procedures along with specs. I knew about the two angles from the risers. I am a dealer for HGE also. Good luck.

OK BUP.. Here is the Serial #. I am not sure if they are they are O's or Zeros in this #. I can never seem to get it right on the mercury parts look site but here goes. OL089625 To me it looks like OL ZERO 89625.

Chris

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