Gasket between riser and manifold

[Arrace]

Hey guys, I was wondering what the point of the block off plate is for the mercruiser 898 that fits between the manifold and riser gaskets? I had a cracked manifold and when I ordered a new one it came with all the gaskets I needed but no new block off plate. Do i need to use the block off plate since it didn't come with it? I'm also wondering what the point of this plate is since there are the water jackets and the holes would go straight from the manifold to the riser but with the plate it wouldn't allow water through? I attached an image below of the old one that I took off and scraped and of the manifold with the gasket on it. If I do need to use the block off plate can I reuse the old one? Thanks!
http://imgur.com/a/Js5IP

 

[Bt Doctur]

It has to do with that type of cooling system

 

[81 Checkmate]

Just to add...I have a 898 without closed cooling (Fresh water cooled) and had to replace the rubber Y-pipe connection boots.....When i took it apart it had no restrictor plate, when i put it back together i installed the restrictor plate with the small hole acording to the manual.....The motor got hot (180) very quickly on muffs. Pulled the plates back out...started it on muffs holds 145 deg and on the water holds 145 - 160 deg.

I am leaving the plate out!


So not sure becouse the manual say's to use the plate without closed cooling system.

 

[Arrace]

I might go ahead and leave them out, but the one manifold I already replaced is on the 898 with the blocker in between the riser so maybe I'll just put the blocker on the one that's out of the boat since it'll be easier to make both sides the same lol. Anyone else have any advice on the matter? Not that I'm not taking your opinion checkmate, but I just want to make sure I'm not going to cause anything that may be a long term effect lol. Thanks!

 

[81 Checkmate]

Yea go ahead and try it with both plates installed.........Keep an eye on the temp gauge, if it gets to 180 deg you will know what the problem is. Keep in mind if you have to take it back apart it may rip the gaskets and they need to be replaced.....BTW next time get mercrusier-OEM gaskets instead of the green ones they seal soooo much better.


Good Luck and lets us know the outcome.

 

[Arrace]

Sure will, I'm running it this weekend for the first time out on the water. So if anything isn't working that I can't find an answer for I'll definitely update you guys. Now as far as oem gaskets, would quicksilver gaskets be the same? I'm kinda new to the marine parts so I'm not certain how reputable they are. I put quicksilver in my outdrive for gear oil for now since I can't get mercruiser High performance outdrive oil near me. Hopefully going to pick some up when I get to the marina around the 4th.

I found these on amazon using the oem part number, thats why I came up with quicksilver. Thanks!
http://www.amazon.com/Mercruiser-Exhaust-Manifold-27-99777-27-997772/dp/B007I95344

 

[81 Checkmate]

Yes Quicksilver is the same as Merc....Gear drive oil is ok too.......... Just me but I buy my gear lube at Wallmart


Yup pick up those gaskets in case you need to pull the plates.

 

[achris]

The use of the block off/restrictor plate will depend on the configuration of your hoses. If the water flow path is from the thermostat housing into one end of the manifold and out the other end and back to the thermostat housing, then you need the plate. If the water comes out the thermostat housing into the manifold at one end and out through the elbow at the other end, then you should not be using the plate. So, if you have a hose at both ends of the manifolds, use the plate, hose only at the front ends, no plate.

 

[Arrace]

Thanks for the input! I have hoses at both ends of the manifolds and one coming out of the side of the riser, so I tossed the plates in anyhow. Good to know that Quicksilver is good, thanks again!

 

[81 Checkmate]

Arrce.....Just courius how it turned out on the lake test.....If you can lets us know......