Exhaust Manifold replacement

[rad1026]

I have a 1989 Chaparral with a merc V-8 260 HP. I purchased the boat 2 years ago and I have done all the maintenance I can do so far including new bellows and impeller. I have not however inspected or replaced the exhaust manifolds. In the next few weeks I will be removing the manifolds and I suspect will be replacing them since I doubt it has ever been done. So my question, I have seen several types of manifolds from direct cast iron replacements to aluminum and some "hi-flow, less restrictive designs". Can you experienced people give me some pros and cons of the different types of manifolds.

Also, when I get these off, what kind of criteria should I be using to determine if they really need to be replaced? What should I be looking for?

Thanks for the help.

 

[tommays]

Re: Exhaust Manifold replacement

ASSUMING the boat has spent its life in freshwater they last a really long time

If you drain them and remove the ellbows you can inspect the condition of the gasket area and get a good idea of there condition

Tommays

 

[rad1026]

Re: Exhaust Manifold replacement

yes freshwater use only. A really long time? 18 years?

 

[tommays]

Re: Exhaust Manifold replacement

Well that is a saltwater manifold at 11 years that is trailered and flushed

I have not seen freshwater manifolds rusting out BUT see who else kicks in and idea



Tommays

 

[Mkos1980]

Re: Exhaust Manifold replacement

Rad, I just purchased a 90 Chaparral 350 V8 last year with the origional manifolds and risers. Freshwater bolt and all, but they were rusting from the outside in from the bottom. When I took them off the insides still looked good. I replaced them with some hi-po Aluminum ones.

 

[rad1026]

Re: Exhaust Manifold replacement

MK, we have the same boat, mine is the 2100SX. So really there is a chance they may not necessarily need to be replaced? I just need to get them off and make a decision at that time. Just curious MK, why did you go with the aluminum? Where they GLM? I can't see a weight savings of like 80lbs. making much difference of a boat of that size.

 

[Mkos1980]

Re: Exhaust Manifold replacement

my father went with the GLM Aluminums and I went with the Aluminum Revolutions. I went a little on the hi-po side since I was doing some engine work and added a small cam. After some dyno test both the Revs and GLM's put out the same HP. It was about 8-10 more then the stock mercury ones. So 80lbs and 10 hp. Not bad. Plus I'm never going to see saltwater. i have ye to hear anything bad about them eather. maybe one case or something, but I hear that with other brands too. The GLM's were 504 shipped to my dads door from ebasic.

 

[Bondo]

Re: Exhaust Manifold replacement

yes freshwater use only. A really long time? 18 years?

Ayuh,....
I've got some kicking around here with over 40 Years on them,+ they're still in nearly New condition......

 

[rad1026]

Re: Exhaust Manifold replacement

Wow, should I really worry about it then? I mean when I drain them I don't get a lot of rust or anything. I guess for the price of some gaskets it would be good to know what kind of shape they are in.

 

[Bondo]

Re: Exhaust Manifold replacement

should I really worry about it then?

Ayuh,.......
For an Hours time,+ a couple $5.00 gaskets,.....

I'd pull the Risers,+ See if your Gasket Surfaces are in Great Condition like the picture Tom posted.....
While you're there,.... Peek down the Y-pipe,+ see what your Flappers are looking like.......

 

[rad1026]

Re: Exhaust Manifold replacement

ok so I pull the risers and if the surfaces look great, leave the manifolds alone or check them too? I assume the flappers in the y pipe are a one way to keep water from coming back in the the risers? What am I looking for there Bondo? Thanks for all the help guys!

 

[Bondo]

Re: Exhaust Manifold replacement

Ayuh,.....

What goes Bad is the Gasket Surfaces,......On Freshwater motors anyways....

If the Gasket Surfaces can be Cleaned up,+ look like the 1 posted by Tom,.....
Throw a New Gasket on it,+ bolt it back together......
And,......
Ayuh,.. The Flappers are pinned into the top of the Y-pipe on your boat.....
If they're in good shape,... No Problem.....
If they're Burnt Up,..... Replace'm.....

 

[tommays]

Re: Exhaust Manifold replacement

Flapper


tommays

 

[rad1026]

Re: Exhaust Manifold replacement

Nice, I'll do it. Thanks everyone! Have a great weekend, I'm heading home to a nice bottle of single malt scotch.

 

[Don S]

Re: Exhaust Manifold replacement

And if the manifolds and risers all look good, get the OEM gaskets, not the aftermarket cardboard look alikes.
Here is the service bulletin on them.

Service Bulletin 99-10