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Old 03-07-2014, 10:32 PM   #1
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Default Manifolds and Risers

Hi,

While I was doing some other mechanical stuff on my boat I removed manifolds and risers and started thinking about reinstalling existing parts or getting new ones. 2013 was my first boating season so I'm still learning. My boat is maxim 2500 from 2002 300 hours (220 fresh water) with single I/O mercruiser 5.7 with bravo 3. The boat was kept for her entire life on CT river so it was fresh water and I brought it into salt water at the beginning of 20013 so it got only 1 salt water season. I'm assuming that manifolds and risers are original. Is there any way to inspect them to figure out if they are qualified for replacement? If yes what will be your recommendation as far of new parts mercruiser or aftermarket? I've seen sierra parts for much less then mercruiser. Just not sure about quality. Also what do you think about ceramic coated? Is it worth of extra money? As always thank you in advance!
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Old 03-08-2014, 12:24 AM   #2
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Hi forbes,
even though theboat was used in fresh water most of it's life the water jackets still rust at some rate just not as bad as with salt water. A lot of folks will tell you 5 years is life for the exhaust but I have seen systems go 10 years with no issues. It depends on fresh/salt, trailer/hi dry/in water, flushing, ...

Inspect the water jacket for scaling. If scaling (flaking rust) then replace it no signs then Ok to reuse but I would not go past 500 hours which if you boat an average of 50 hours per year will give 4 more years.

I have sierra on my boat now and think they make a good manifold. Others do as well but the cheaper you go the shorter they will last IMO. Ceramic coating will increase life but not sure if extra life exceeds the cost.

Is the system wet or dry joint? See link

http://www.ebasicpower.com/faq/dryjointexhaust.htm
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Old 03-08-2014, 03:28 AM   #3
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So many variables affect the life of cast iron exhaust parts. Our son has our 1993 Regal (350 Alpha on a trailer) with at least 1500 hours of North Carolina fresh water use and is still running the original manifolds. Our 1998 Maxum 3700 with twin 7.4 (650 hrs) also has the original parts. A few weeks back I started getting an occasional miss in the starboard engine. Turns out that the original gasket between the outboard manifold and the 3" rise developed a tiny leak. Of course the water passages are red with rust but there are no signs of significant deterioration and the gasket surfaces cleaned up nicely. I'll either replace all the gaskets and run another year or replace everything now. Need to make that decision this weekend. We are on the boat tonight but unfortunately stuck in the slip.
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Old 03-08-2014, 11:30 AM   #4
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Thanks guys!

Its a wet joint system. Is it possible to change it to dry joint without replacing additional parts and making adjustments?

I'll have a closer look at the manifolds this weekend trying to determined the shape of them. Saying that they are original is just my wild guess looking at the top coating etc. Its possible that a previous owner replaced them at some point. I just don't know much history about the boat.

Mike, Had the same thoughts about ceramic coating. It probably make sense to don't spend extra $ on ceramic coating and instead replace them more often.
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Old 03-08-2014, 12:46 PM   #5
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After re-reading te link I provided dry joint came out in 2005. As far as switching over I have heard so who said they did but not sure if it is a direct swap. My concerns would be raw water host to manifold may be different although this would be pretty easy to correct. My bigger concern is are the elbows similar so that they align with the exhaust hose and insert fully. Merc has changed the elbow down angle in the past.

You may want to e-mail merc and ask the question
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Old 03-08-2014, 03:07 PM   #6
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Mike,

I think thats exactly the case. It looks like the exhaust will have to be changed as well. At this point its not worth it to go this route.
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Old 03-08-2014, 03:35 PM   #7
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forbes wet joint has been used ever since inboard boats have been around so this is a proven design, therefore no worries.
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Old 03-08-2014, 10:19 PM   #8
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I would definitely replace them. I also have a 2002 that I keep in brackish water. I replaced them three yrs ago.. Better to be proactive and replace them before they rust out... I used Barr parts for a big savings. Sierra parts are good too...
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Old 03-08-2014, 11:16 PM   #9
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Yep if in doubt replace them. Sure beats a $5k engine replacement.
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Old 03-16-2014, 12:25 AM   #10
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I bought my maxum used with 400 hrs on it. I changed the manifolds, risers, and elbows (elbows don't really need to be changed) as well as changed all the fluids in the motor, v-drive, and generator. I'm glad I popped the manis off cause they were starting to show serious signs of rust. It gave me a piece of mind that I started with major wear parts new.

Shop around on ebay, ect. for the manifolds and risers. You can usually get much better deals than buying from your local mercruiser dealer. I would suggest replacing any hoses and worm clamps attached to the manifolds/risers that show signs of wear as well.
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