3.0 Mercruiser Riser to Manifold Leak

Floridaguy800 · Jun 7, 2009

I have a 1999 3.0 L Mercruiser, the leak looks very small, but I want everything to be working properly, it's between the riser and exhaust manifold. My biggest concern is, is this just in need of a new gasket? Was it purely a gasket failure, or the result of something else going wrong?

Also, the back portion of the exhaust manifold looks to have a good deal of rust from this small leak, should I be concerned?

I've taken some photos so you can see what I'm looking at, thanks in advance for your help!

riser

riser up close

leak of water onto manifold

back of manifold quite rusted

Don S · Jun 7, 2009

Re: 3.0 Mercruiser Riser to Manifold Leak

Clean the gasket surfaces and inspect. They should be clean and shiny metal. Then repost with pictures of the cleaned gasket surfaces. That manifold looks awfully thin on the inner web.

Floridaguy800 · Jun 7, 2009

Re: 3.0 Mercruiser Riser to Manifold Leak

I'm going to clean the surfaces and repost. Is there a tutorial or typical procedure for gasket removal?

Isaacm1986 · Jun 7, 2009

Re: 3.0 Mercruiser Riser to Manifold Leak

I have a 1976 24ft Fiberform, has a 351 windsor in it, any way i just had to replace the risers on my manifold system. the channels that seperate the exhaust from the water were so rusted through that they were mixing and dumping water in my oil. Why you have them off, you might just check them to make sure they are still in good shape.

Floridaguy800 · Jun 7, 2009

Re: 3.0 Mercruiser Riser to Manifold Leak

Started to clean the riser, I think I'm going to have to replace it though...it looks pretty rough and I can't even begin to get into this clogged water jacket...whatcha guys think?

Don S · Jun 7, 2009

Re: 3.0 Mercruiser Riser to Manifold Leak

Clean the gasket surface, not the inside of the water passages. If the water passages are plugged up, yes it needs replaced. What I was wanting to see was the manifold gasket surface.

Floridaguy800 · Jun 7, 2009

Re: 3.0 Mercruiser Riser to Manifold Leak

Yeah, I can't begin to get that part of the gasket over the covered jacket off though, it's like on big bonded rusted piece.. Are there only 3 water jackets on this?? I was looking at a new gasket for it online and it had only 3 holes for water jackets.

Floridaguy800 · Jun 8, 2009

Re: 3.0 Mercruiser Riser to Manifold Leak

After quite a bit of scraping/sanding I'm only about halfway done cleaning the gasket off, it's like cast iron itself, and I'm just now getting to the actual bare metal. From the looks of the passages and the big chunks visible inside the jackets, I think I'm safest getting a replacement manifold/riser...Any tips on removing the exhaust manifold?

cooter2506 · Jun 8, 2009

Re: 3.0 Mercruiser Riser to Manifold Leak

IMHO it needs replaced

Floridaguy800 · Jun 8, 2009

Re: 3.0 Mercruiser Riser to Manifold Leak

Yeah that's kinda what I thought...I yanked the exhaust manifold off too...I think it needs to be replaced w/the riser...Anyone know where I can get the best deal on an exhaust manifold+riser? Is GLM an okay replacement?

Exhaust Manifold

cooter2506 · Jun 9, 2009

Re: 3.0 Mercruiser Riser to Manifold Leak

OH MY! Yep replace both. Iboats sells them. Also check ebay. Numerous places sell them just need too shop around alittle.

TommyRox · Oct 26, 2011

Re: 3.0 Mercruiser Riser to Manifold Leak

Oh lord I have the exact same issue on MY 99 BowRider Mercruiser 3.0. I had to replace my exhaust flapper last week and now that it's all put back together - leaks water. I have taken it apart and clean it to bare shiny metal - almost looks new and replaced the gasket. SeaRay says to install gasket dry so that was the last thing I tried - still leaks. Before I used an RTV gasket sealer and cleaned and removed 2 times - both times leaking. I cannot imagine anything is warped...is there a secret to getting this leak to stop? I don't think the riser or manifold in my case needs to be replaced as they look brand new. Will post pics if needed...

Thanks in advance. GREATLY appreciate any feedback

TommyRox

Don S · Oct 26, 2011

Re: 3.0 Mercruiser Riser to Manifold Leak

You need to start your own thread, not hijack old threads.
might want to read the announcement at the top of this forum.

Here is the announcement.
http://forums.iboats.com/announcement.php?f=21

3.0 Mercruiser Riser to Manifold Leak

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