Recommended site for Risers & Manifolds

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Keith the Cop

Member
Oct 13, 2009
173
Long Island
Boat Info
2000 400DB
1989 340 Sundancer (Gone but not forgotten)
Engines
3116 Cats
I have to replace the risers and exhaust manifolds on my 89 340DA. It has big block mercruisers.

Where do our members shop for such items?
 
I bought my boat this past summer and the previous owner said I should replace mine before next season. How do you know when they need replaced?
 
Deckworks1 said:
I bought my boat this past summer and the previous owner said I should replace mine before next season. How do you know when they need replaced?
Click to expand...
As a rule of thumb I was told to replace them every five years by my mechanic who is also a close friend. :smt089
 
I bought OEM Mercruiser on ebay from Doug Russell Marine. Be careful of some of the less expensive brands.
 
Deckworks1 said:
I bought my boat this past summer and the previous owner said I should replace mine before next season. How do you know when they need replaced?
Click to expand...

You should pull a riser on each motor at the very least each season to visually inspect it. It is easy, takes only a couple of minutes, and a new gasket is cheap.
If you want to be a little more cautious, you can pull the manifolds also. It takes a little more time, but isn't complicated, and a set of gaskets is a small price to pay for piece of mind.
If you see any evidence of corrosion between the inner walls that seperate the water from the exhaust gases, buy new manifolds and risers.
I always makes sure to put some anti-seize compound on the threads of my bolts before putting them back in. It makes future removal for inspection and/or replacement much easier.
 
On my 270 if I unbolt the risers to try to lift them up the rubber exhaust linkage bit will foul with the top of the engine hatch - and I can't move them forwards beacuse I can't get the bolt threads out - there's nut on the top, not a bolt head - I can't remember the right word for these but you know what I mean...!

Any tips? - Other than having to take the manifold off and drop if down??

My manifolds/risers are 11 years old now so I reckon I'm due a change!

Cheers,

Nigel.
 
Take it from Rod and I - "*******" has the best prices around, if you want OEM. I would NOT use aftermarket stuff. I can't believe they won't let me type the name. Let's try it this way...

Bee Oh A Tee F I X dot Com.
 
Thanks for the Technical help. I happen to have time next week to inspect.
Sweet, I get to spend some winter time with my baby.
 
nigel said:
On my 270 if I unbolt the risers to try to lift them up the rubber exhaust linkage bit will foul with the top of the engine hatch - and I can't move them forwards beacuse I can't get the bolt threads out - there's nut on the top, not a bolt head - I can't remember the right word for these but you know what I mean...!

Any tips? - Other than having to take the manifold off and drop if down??

My manifolds/risers are 11 years old now so I reckon I'm due a change!

Cheers,

Nigel.
Click to expand...

I loosen the clamp on the rubber exhaust extension and remove the riser from it.
If I'm hearing you correctly: You have studs extending up out from your mainfolds. The risers are lowered on the studs, and then secured with nuts.
Does that sound like what you have?
If so, double nut it and remove the studs.
You do this by installing a second nut on top of the first one and locking them together by using a wrench on each and turning them towards each other.
Once you have done the double nut thing; Get a wrench on the lower nut and turn the stud out. The upper nut will keep the lower nut locked in place on the stud so you can use it like the head on a bolt.
Once you have all of the studs out, loosen the big clamps that lock the risers in to the rubber exhaust hoses and twist the risers out of those hoses.
I would replace the studs and nuts with bolts when you re-assemble.
 
No problem! Glad I could help.
The one thing I forgot to mention. Pick up a small bottle of anti-seize compound at your local auto supply store. Put a little coating of it on the threads of the bolts (or studs if you choose to use those again) before you thread them back in to place. It will make future removal nice and easy.
 
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Also be sure to torque them to spec. 25 or 30 ft-lb. Proper compression of that stupid gasket is key.
 
Unless I am mistaken my studs (previously bolts) penetrate into the manifold cooling chamber. You must use sealant on the threads to avoid leaks not anti-seize.
 
The bolts do not seal anything - the gaskets do. You really don't need antiseize on the elbow/riser studs/bolts either. There is no intense heat and very little chance of corrosion. Probably wouldn't hurt but likely not necessary.
 
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