Exhaust manifold and riser gasket sealant?

[villain style]

I am replacing my exhaust manifold and risers gaskets with new ones. Should I use a sealant? If so, which one and do I apply on both sides of gasket????? Engines are 95 GM 350 inboards with closed cooling.....

Thanks... Oh and risers are stainless steel if that makes any difference....

 

[fc3]

Mercruiser says no. But some guys I know use perfect seal on them. I forgot what I did when I put new manifolds, risers, and elbows on Just Ducky. Hopefully, that's the last time I do gas engine exhausts!

Best regards,
Frank

 

[MLauman]

You'll get different answers to this but I found that most people put no sealant on the exhaust manifold gasket (per Merc) and a light coating on each side of the riser/elbow ones. I used black Permatex.

 

[JVM225]

I didn't use any sealant on mine and I never had a problem.

 

[fc3]

I've been thinking about it and I'm pretty sure I used perfect seal on manifold to riser and riser to elbow joints. Nothing, of course, on the head to manifold joint. I remember also using perfect seal on the raw water hoses and drains to eliminate that occasional drip.

Best regards,
Frank

 

[Salty Dog - LI]

My marine mechanic uses OSCO "green" gaskets dry. He said the OSCO gaskets have something in the gaskets that provides a great seal. The key is to make sure the mating surfaces of the exhaust parts are not damaged. Clean them well and polish with emory paper, not sand paper! The MERC gaskets can leak dry.

I put on the green OSCO gaskets specified for my engine when I replaced the exhaust manifolds, 3" extensions, and exhaust elbows last spring. No leaks!

Good luck!

 

[H2ONUT]

I have used Sierra gaskets. They are "green" also, and seem much heavier than the Mercruiser gaskets. I use a spray from NAPA on gaskets. It is red and tacky. I use it for all gaskets, marine and automotive.

 

[douglee25]

I would strongly suggest using some sort of sealant because the mating surfaces are never 100% true and are usually pitted to some degreee. I would recommend Permatex The Right Stuff or Permatex Form A Gasket #2. Either or will stay flexible to create a good seal. The last thing you want to do is have a small leak and have water in your cylinders.

http://www.permatex.com/products/Au...uto_Permatex_the_Right_Stuff_Gasket_Maker.htm

http://www.permatex.com/products/Au.../auto_Permatex_Form-A-Gasket_No_2_Sealant.htm

Doug

 

[digster868]

It really is a great question... because so much depends upon the manifold or riser gaskets you are using. For the gaskets that I use I never use a sealant.

When you buy the gaskets, most times the manufacturer will tell you whether or not to use any. A sincere, good quality gasket for manifold or riser will not require sealant.

With Kindest Regards,
Digger

 

[digster868]

Oh, and with all respect to Doug.. pitting may be a problem. Unfortunately, some of the sealants you use may react with the gasket itself. He may have a bit more knowledge there than I do. There can be some strange reactions in saltwater environments with aftermarket gaskets and different materials.

Digger

 

[SAshton]

I just did replaced manifolds/risers & I used the quicksilver perfect seal....... I use it on bolts, gaskets, almost everything

 

[2000SEARAY280SS]

I've been thinking about it and I'm pretty sure I used perfect seal on manifold to riser and riser to elbow joints. Nothing, of course, on the head to manifold joint. I remember also using perfect seal on the raw water hoses and drains to eliminate that occasional drip.

Best regards,
Frank

I used Perfect seal on my twin 5.7’s and really liked the way it self leveled and flowed onto the mating surfaces. I used the Quicksilver gaskets with no problems. Make sure you use the proper torque for your engine.

 

[villain style]

Thanks guys. Wow, seems like there is alot of different opinions with positive results. I think I'll use a little and torque to spec. I purchased the Quicksilver replacement gaskets but they did not come with any installation recommendations.... I believe torque is 33 ft lbs. Sound right???

 

[Leafy Isle]

Hi there, related to this thread.... are your stainless risers the OEM Merc ones? I have twins and one side has the stainless, one cast iron. Where did you find the replacement stainless risers and does anyone know why Merc discontinued them?

Thanks.....

 

[villain style]

They are the original risers. I took the exhauset manifolds/risers off one engine to check and prepare for replacement of them (boat is new to me within last 2 years and I was not sure when they were ever maintained/replaced) and saw that they were stainless steel. They looked in very good condition too........ So I bought new gaskets and am preparing to reinstall. I think Merc discontinued making the stainless steel risers beause of the cost to manufacture them....

 

[SAshton]

torque rating is 30-35 ft lbs and you'll be OK....Retorque after a few uses(10hrs or so)