2007 Mercruiser 3.0L Manifold/Riser change *need advice*

[Jiminthekeys]

I hope someone her can give me some sound advice on my corrosion concern. I was changing the old in my 2007 sea Ray with a 3.0 Mercruiser inline 4cyl. During the maintenance I noticed a build up of running rust from the riser to manifold and also a bit of rust/corrossion on the lower rear of the block. I purchased the boat last year and as far as I know it is the original riser and definetly the original manifold. I figured the riser was shot or the gasket so I removed the riser as well as the manifold to inspect.
What I found:
-Riser heavily rusted and corroded. Needs replacement
-Riser to manifold gasket; failed and started to leak. (mostly to the outside from what I can tell.
-manifold passages looks great to me except the mating surface the got eaten to thin on the riser side which I believe warrants immediat replacement as well as a spot on the #4 cyl mating corner on manifold that got eaten by leakage.

**My big concern is with the mating surface from manifold to head. The #4 corner on both shows a small amount of corrosion and unevenness. The corrossion pitted the corner on the heads so it's not like I can file anything down. I included pictures of this so maybe someone can advise me on what I should do with the head mating surface if anything at all. Maybe the gasket still has enough surface to seal? There did not seems to be any leakage from the manifold to head before taking the manifold and riser out and the manful/head gasket looked normal to me.

Also how does the flapper look?

Thanks for any help, this is my first time doing anything on a sterndrive other than oil, gearlube, and impeller changes.

 

[Don S]

Re: 2007 Mercruiser 3.0L Manifold/Riser change *need advice*

You need a new manifold and elbow. The gasket surfaces are gone. You must be in salt water, and all I can say is you are real lucky the engine isn't locked up from salt water in the cylinders.

 

[Jiminthekeys]

Re: 2007 Mercruiser 3.0L Manifold/Riser change *need advice*

Thanks Don. Yes I will definitely be replacing both the manifold and riser. After I took these off and realized the extent of gasket failure and water intrusion I new I was lucky. I was just surprised it was this bad on a 5 yr old engine with 230hrs. that gets pulled up on my davits every time it comes back, flushed religiously with fresh water and salt away...

From looking into the head all valves are clean and there is no corrosion in the cylinders there. My only concern at this point is the little bit of corrosion on the corner of the head gasket surface. Do I need to do anything about that? If so what would you recommend? Or is there plenty of gasket surface intact to make a proper seal?

Here's another few pics of the gasket surface on the head. Only the surface around that #4 port is corroded, all the rest is nice and smooth.

 

[Jiminthekeys]

Re: 2007 Mercruiser 3.0L Manifold/Riser change *need advice*

Anyone have any suggestions on what i should do with the corrossion on head mating surface? Do i need to have it machined before i install a new manifold?

 

[dingdongs]

Re: 2007 Mercruiser 3.0L Manifold/Riser change *need advice*

should be ok but a compression check will see if internals are sound.a clean up and follow with a nice coat of hammerite smooth paint will save any further rusting of external block.salt water left in the bilge is a recipe for rusting like this!

 

[Jiminthekeys]

Re: 2007 Mercruiser 3.0L Manifold/Riser change *need advice*

One thing that is puzzling me is why does my exhaust manifold have 4 water passages but the riser only 3? With just a gasket blocking one passage off is this normal??? Maybe this is why they started leaking?

 

[Bondo]

Re: 2007 Mercruiser 3.0L Manifold/Riser change *need advice*

One thing that is puzzling me is why does my exhaust manifold have 4 water passages but the riser only 3? With just a gasket blocking one passage off is this normal??? Maybe this is why they started leaking?

Ayuh,... That's how the flow is regulated,... It didn't Cause anything,... Rust caused yer problems...

 

[Jiminthekeys]

Re: 2007 Mercruiser 3.0L Manifold/Riser change *need advice*

Ok. Thanks bond-o.