risers after 8 yrs in salt water

nickysc

nickysc

New Member
Jul 1, 2007
581
Springfield SC
Boat Info
270se sundancer
Engines
7.4mpi w/BravoIII
There has been a lot of questions about risers and manifolds on raw water cooled gas engines. Here is a picture of a 3in riser block that has been in service for 8 yrs. Boat was dry stacked and flushed after every use.
When we removed the riser, gasket was still in tack. There was no sign of leaking, or bad seal. When we inspected the block real close, quickly realized we caught it just in time. Block has been sitting on back porch for 3 weeks. Sun rain and just drying out, has caused the rust to fall off. Heres what we had. Both risers, manifolds elboes and down pipes will be replaced with new.

https://picasaweb.google.com/102002628477428471286/20110304?authkey=Gv1sRgCPq_5uOQnfbkLA#
 
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Amazing you didn't lose that engine. Have you done a compression and blow-by test? I wouldn't say you dodged the bullet until after you have those results.
 
fc3 said:
Amazing you didn't lose that engine. Have you done a compression and blow-by test? I wouldn't say you dodged the bullet until after you have those results.
Click to expand...

I agree, bullet was dodged. so far no sign of any damage. Engine was running clean and strong. Owner took it out on a cruise 1 week prier to pulling. I'll remove spark plugs while engine is on stand.
 
Even if it miraculously passes a compression test I would be concerned about the exhaust valve stems that are exposed in the exhaust stream between the valve head and the guide. look carefully
 
The block didn't look that bad when we first took it off. Everything looked solid. After it was exposed to air and dried, the deterioration started showing. I took a pocket knife and the rust just flaked away.
When looking at these exhaust systems you need to look closely. Rust runs deep.
This riser was on a 1997 454 in a 290 sundancer.
 
Spashed today. With new risers, manifolds,and elboes and lots of other new parts. All is well engine is running stronger than ever.
 
dicor said:
WOW you're a luck guy!!! Was there any signs of wear on the outside of the riser? Rust/corrosion at the joint face?
Click to expand...

I agree. Nice catch and luck was on your side. Maybe you should play the lottery this weekend!
 
There was no signs of any kind on the outside, The gaskets were still stuck and sealed. I honistly don't think the engine would have survived this summer. The thin place was below the gasket surface.
 
The boat I just bought has 6 year old riser/manifolds. It's been used mainly in salt water. This type of common failure scares then Hell out of me. I think the first thing I'll do, within the next 2 weeks will be to remove the risers and check them out. What a weak link. You would think by now there would be some type of fail-safe that would prevent you from wiping out a $10,000 motor. They have gotten closer with the dry joint manifold but still not there.
 
Wow, that is rough. When I pulled my risers off my 350 not long ago I found the opposite in my system. The galleys had actually clogged up with rust and sediment all along the lower portion of the 90* elbow, and the contact area with the manifold was about the same, the galleys were all clogged and much smaller than normal. I ran a grinding stone on it just to see what really was up and it seems they were all corroded to the point of no return. I will try and get some pics tonight. You would think they would use something more corrosion resistant or at least some sort of coating in the system to prevent that sort of thing.
 
The mode of failure shown in the original posters pictures (ie corrosion between waterjacket and exhaust gas chamber at the manifold mating surfaces) cant happen with the dry joint manifolds, it can still corrode through elsewhere along the wall seperating the coolant from the exhaust gasses, but I understand this will take a lot longer than the corrosion between mating surfaces on the non dry joint manifolds
 
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