350Mag Mpi (2009) Exhaust riser and manifold change

[silver_power]

Hello, i own a Wellcraft nova spyder with a new 350Mag Mpi (MY2009) and i was wondering if anybody can inform me every how many years should i change the exhaust risers for not having problems. I had similar problems with my old engine and i do not want to have the same with new.
Thank you very much.

 

[Don S]

Re: 350Mag Mpi (2009) Exhaust riser and manifold change

Not enough information to answer your question.
What went wrong with your previous manifolds, and what year were they? Do you boat in salt water, if so how much?
If you had the older style manifolds that failed at the riser/manifold junction, your new type manifolds (dryjoint) is designed to prevent that.

 

[silver_power]

Re: 350Mag Mpi (2009) Exhaust riser and manifold change

Well , my old engine at which i had this problem was a 1992 350LX mercruiser. Yes,as i am in Greece, the boat runs in Aegean sea. The exhaust manifolds went rusty and so during the winter period, salt water entered into the cylinder and 2 cylinders became rusty.
When i fixed the internal of the engine , i changed both the exhaust manifolds and the risers also. The mechanic i had then told me that because of the years (10years), the manifolds went rusty and the water passed into the cylinders.
Now my new engine is a 2009 350Mag Mpi and as i do not want to have similar problems i ask if someone knows every how many years shall i change the manifolds in the future.
By the way, does mercruiser has developed any kind of a new style manifolds and use at the newer engines like mine in order not to have similar problems with rust and so not to allow the water to pass into the combustion chamber?. Please inform me if you know something.
Thank you very much.

 

[Bondo]

Re: 350Mag Mpi (2009) Exhaust riser and manifold change

i ask if someone knows every how many years shall i change the manifolds in the future.
By the way, does mercruiser has developed any kind of a new style manifolds and use at the newer engines like mine in order not to have similar problems with rust and so not to allow the water to pass into the combustion chamber?

Ayuh,... You should remove the risers, 'n check the castings after, say 5 years, then replace as necessary...

Merc has the newer "Dry Joint" manifolds/ risers...
Donno if they're Better or not...

 

[Don S]

Re: 350Mag Mpi (2009) Exhaust riser and manifold change

By the way, does mercruiser has developed any kind of a new style manifolds and use at the newer engines like mine in order not to have similar problems with rust and so not to allow the water to pass into the combustion chamber?. Please inform me if you know something.

Yes they did, they use the new Dryjoint type exhauset manifolds and risers as I mentioned in my first post.

If you had the older style manifolds that failed at the riser/manifold junction, your new type manifolds (dryjoint) is designed to prevent that.

The old style manifolds had a very narrow 1/4" cast iron wall between the water and exhaust cavities, and they would fail at the junction where the riser and manifold went together. The red areas in this picture show where the areas were that would fail.

In this next picture, you will see the dryjoint type manifolds. The area that failed all the time no longer exists.
The water going to the riser now has external passages shown below in blue.

So the problem with water into the engine from leaky gaskets doesn't exist anymore. The only problem you will run into is when they start getting plugged up with rust and corrosion. This will be seen as increased engine temps, not water in the engine.

 

[Volphin]

Re: 350Mag Mpi (2009) Exhaust riser and manifold change

Why not go to an aluminum manifold with anodes? Hey, it works on our out drives...

V

 

[Don S]

Re: 350Mag Mpi (2009) Exhaust riser and manifold change

Aluminum manifolds is the worst possible thing you could do for a salt water boat.

 

[silver_power]

Re: 350Mag Mpi (2009) Exhaust riser and manifold change

I see what you mean saying dryjoint manifolds,......
Why mercruiser does not use stainless steel manifolds,?It is a matter of cost or any other reason?

 

[Riegfrghtl]

Re: 350Mag Mpi (2009) Exhaust riser and manifold change

Price. Extremely expensive!

 

[scoflaw]

Re: 350Mag Mpi (2009) Exhaust riser and manifold change

What year did merc go to the dry joint?