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Gaskets on exhaust riser

adam_g

adam_g

Contributing Member
Doing my winter thing on my &#

Doing my winter thing on my '95 7.4 L Searay. When I pulled the riser elbows off of the manifolds there were no gaskets. Metal to metal with no sign of any kind of sealer. I do not believe these have ever been off before. The engine has 200 hours. I notice that Sierra makes gaskets for this. There never was any sign of leaking. Could it have left the factory like this and why?
 
"GM did that on many auto engi

"GM did that on many auto engines for exhaust mans. Look at the money saved on gaskets. I don't know if Merc. did it on purpose but if the parts are machined to a close tolerance, gaskets aren't necessarily needed."
 
right. like GM manifold mating

right. like GM manifold mating surfaces against the head. No gaskets. Nothing. Seems odd but it works.
 
"I'd be real nervous about

"I'd be real nervous about no gaskets in the manifold to elbow joints, considering the cyclic heating and cooling and differential expansion involved.
With water jackets surrounding the exhaust passages and the damage that can result from water leaking into the manifolds on shutdown, I think I would strongly consider putting them back together with gaskets and Loctite 510 sealer as specified in Mercs service bulletin no 99-10.

To me the minor cost of gaskets and doing it right far outweighs the potential downside of water leaking into the cylinders.

Just my thoughts,
Rod"
 
I'm with Rod. You would n

I'm with Rod. You would not believe how much expensive damage a water leak at the manifold/ riser joint can cause.

Jeff
 
"I hate to re-engineer somethi

"I hate to re-engineer something that came from the factory. Maybe Merc's thinking is that a leak resulting from metal on metal would be much smaller than a hidden leak that occurred from a fiber gasket that lost a chunk of material between the exhaust passage and the water jacket. The thin section between the two passages could possibly lead to this. I think that I will send this thread to Mercury for their comments. All said, I just ordered two gaskets."
 
"More Confusing than ever
My

"More Confusing than ever
My note to Mercury:

While doing routine maintenance and winterizing I removed the riser elbows
off of the ex. manifolds. To my suprise, there were no gaskets and no
sealant. The finish on the faces were very smooth (ground and lapped?). I
do not believe that these have ever been off (200 hours on engine)and there
is no sign of leaking. Did this leave the factory like this? There are
several service bulletins floating around (99-10 and 2001-13) that are
confusing. What do you recommend for putting this back together. I would
prefer not to use a permanent type of sealer since I want to inspect the
manifolds at least every year. The boat has raw water cooling and is run on
a very clean lake.

The first reply from Merc:
Thank you for your inquiry. I am not sure why there was no gasket on
there because it would have come standard with a 2-slot gasket from the
factory. Below I have attached some information that should help you
determine what part number you may need. I hope this helps. Thank you.

Best regards,

Andrew Bambrough
Consumer Service Specialist
MerCruiser Customer Service

My second question:

Andrew,
Do you recommend any type of sealant be used or can I install it "dry"?
Thanks

His answer:
No, that is a dry gasket.

The only problem with this is that I saw a sevice bulletin that showed the gaskets smeared with Loctite gasket sealer. All I want for Christmas is no water in my combustion chamber."
 
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