Riser Installation

[CDAWaves]

I pulled my port side riser to inspect the condition for preventative maintenance. This is the first time it has been disassembled since new. I was surprised that there was not a gasket between the manifold and riser. There are 2 small round rubber rings that are inset into the manifold which appear to seal the water channel between the 2 parts (manifold and riser). The rest of the area is just bare metal on metal.

I have looked online for replacement gaskets and found the rubber rings(labeled old style) and I see a pre 2011 and post 2011 regular gasket. I am wondering if I should just install new rubber rings with no gasket like it was originally or use the rubber rings with the pre-2011 gasket or no rubber rings and just the gasket. The service manual I have only addresses the manifold to engine removal and installation. It does not show anything about the riser to manifold connection. Here are some questions.

-Do I install both the rubber rings and gasket? Just use rubber rings and the rest is metal on metal? Metal on metal doesn't sit right with me, but I usually like to do what was OEM. Rubber rings and thin layer of liquid gasket? No rubber rings and just the gasket? If I need liquid gasket what kind for this application?

-What is the required torque for the 4 bolts holding the riser on the manifold?

The engine is from a 2005 24V
Marine Power 5.7 340HP Manufactured in 4/2005

The riser is the MP2K aluminum - http://www.michiganmotorz.com/marine...age-p-808.html
This is the rubber ring seal - http://marineenginedepot.com/MP/Mari...r-(Old-style)/
This is the pre-2011 gasket - http://marineenginedepot.com/MP/Mari...er-(Pre-2011)/

[dom w. forte]

Go back just with the o rings , and about 20ft lbs , add some anti seize .

[Thegerman618]

just curious what was the condition of the risers? I assume a little rust with some carbon build up but anything us 5.7 owners should keep an eye out for?

[CDAWaves]

The riser and manifold were in surprisingly good shape. Really no rust flaking in the water jackets and carbon build up is not a problem. The boat has been in fresh water only to my knowledge and the engine has about 600 hours. Given the condition I will not worry about checking them again for a long time. I didn't know it until I removed them that the risers are aluminum so rusting isn't a problem.

[dom w. forte]

My 2004 has 2500 hrs and have never been apart, their are no external stains of any kind , the o- ring style were much better then the gasket style.

[ktulu07]

Riser installation

My 2004 has 2500 hrs and have never been apart, their are no external stains of any kind , the o- ring style were much better then the gasket style.

I am in the process of reinstalling the riser on my engine. Same model as this post. Marine Power 5.7 circa 2005. I bought both the gasket and o-rings.

My question is where to put the o-rings. There doesn't seem to be any place for them to sit. Do I just put them around the bolts on opposite corners? The gasket seems to have a cut out for them so I could install both.

Excuse my rudimentary drawing but, below is what I was thinking.

Regards,
Steve

Annotation 2020-04-20 100858.jpg

[secr1973]

So is it gasket and o-rings or just o-rings? When I pulled mine apart there was some kind of thin sealant between the surfaces.

[boatwakes]

If you pulled it apart and there were only o-rings, replace the o-rings and go. If there was a gasket, replace the gasket after scraping away all previous gasket material and making sure not to damage the flange face. If there was hi-temp RTV, someone has been in there before you and did not perform the repair correctly (NEVER USE RTV WHEN INSTALLING ANY RISER TO MANIFOLD). Because the manifolds and risers are aluminum, they are extremely problematic when used in saltwater but freshwater use they will last a very long time. Aluminum does not rust but it will oxidize and literally crumble and it does this in the water passages, a place that cannot be inspected visually. Use your discretion but we recommend replacement per manufacturer's guidelines.