Took my Manifolds and Risers apart….

saopm

Active Member
Oct 6, 2010
916
North Fork - Long Island, NY
Boat Info
2005 420 Sedan Bridge
Engines
Cummins 450
I took my raw water cooled dry joint Manifolds and Risers apart. They look pretty good as far as I can see looking into the water ports. The exhaust ends of the risers look really good too with no scaling on them. Overall they have 8 salt water seasons on them and only about 125hrs of run time. At this point I feel like I might be wasting my money replacing everything. Can anyone convince me otherwise?
 
we did my buddies on his '03 280 at the begining of last season with the same results - the oulets had no scaleing at all and the passages were super clean seemed to be a waste scrapping them - I inspected mine as I had to remove one for access on another job and it looked even better - some would say the manifolds may be getting "thin" where you can't see but I would think there would need to be scale inside for them to be getting bad. I have also been told the life is not linear - when they start to go they go quick. I dont know if there is any truth in that but it makes sense. Now that my boat is dry stacked I expect to get more time out of them, but I will check them every year and replace when necessary. Manifolds and risers are expensive - but they are a lot cheaper than replacing an engine because you thought you could get one more season......
 
Was is tough to do? I don't know when they were last off my boat. I think I'll add it to the ever growing spring list.
 
By the looks of it I am about 5 years premature on this maintenance. So far it was relatively easy to get it all apart. I probably spent about 1.5 hours tearing it down. The can of worms is open.....
 
Tim, that's good to know. I have fresh water cooled Horizons and I was wondering when I should start to get nervous about checking them?
 
Tim, that's good to know. I have fresh water cooled Horizons and I was wondering when I should start to get nervous about checking them?

You are probably good till at least 10 years out, but you might want to remove and inspect the risers before then. At least you don't have to replace your manifolds since they are fresh water cooled. At this point I'm still scratching my head on what to do, buy new gaskets and put it back together or replace everything. I'm leaning towards replacing everything so I don't have to worry about it for the next 10 year and if I sell the boat in a few years then it is a good selling point. :huh:
 
You are probably good till at least 10 years out, but you might want to remove and inspect the risers before then. At least you don't have to replace your manifolds since they are fresh water cooled. At this point I'm still scratching my head on what to do, buy new gaskets and put it back together or replace everything. I'm leaning towards replacing everything so I don't have to worry about it for the next 10 year and if I sell the boat in a few years then it is a good selling point. :huh:

I'm not a salt water boater, nor do I have any experience as one, but I wouldn't go to all that expense at this point. Unless I am missing something, if they visually check out good, I would consider it good to go, if it were my boat.
1.5 hours labour and new gaskets in two years time should be able to catch any problems. Check your oil daily and don't worry too much.
Just my opinion.
 
When we replaced mine, they looked good at first. But when we got them off completely there were several thin spots and a couple almost plugged ports. I also found my flapper on port engine was bad. I'm glad I decided to do the job. Now she has a deeper "growl" while under way and almost seems to have a little better acceleration. Could just be mental, at least I know she will be good as long as I'm going to keep her!
 
I'm still up in the air over mine. I had MM remove and inspect mine last year and they said I should replace next year (now) but my temps are holding perfect and no noticable difference with sound or water flow. I feel like I need to replace them for piece of mind. I'm also leaning towards the Hi-Tek stainless steel one piece manifolds due to lighter weight and possible increase performance. I'm also hoping that I will get more life out of them. The costs is the same as repalcing with OEM Mercruiser parts.
 
I've got 4 seasons in salt water on my RWC 260 Mercs and I'm trying to decide if I should change just the risers or if I should go all in and replace the manifolds too. Twin engines makes the decision twice as expensive. Right now, I'm leaning towards replacing risers only as I flush after each use and don't rack up alot of hours per season. Risers are where I think the weak link is. What say you?
 
Visual inspection is only where you can see. I took mine off since I was replacing them because I had hot spots with a infrared thermometer. They looked clean where I could see them. I took them and threw them on the ground for a couple of weekends before I threw them out. In those couple of weeks, what a difference. Scale showed up bad. air got to them and they just fell apart.

The best way to determine if you need to replace them is using a thermometer. There should be a constant reading as you check all areas. I had several spots where there was a 20 degree difference. This is the indication that there is closing of the channels which the water or coolant is traveling.

I also read somewhere that manifolds and heat risers are only good for about 8 years on salt water and about 10 to 12 years in fresh water. Mine were the originals and was 22 years old. All 22 years was fresh water. To me, the price of the manifolds and risers was much cheaper than an engine.
 
The dry joint exhaust eliminated the problem of gasket failure causing a catastrophic engine failure, but they do not prevent the cast iron walls in the elbows from corroding away. Unfortunately, there is no way to inspect the walls of the elbows unless you crack them open. Of course, if you do that then you have to replace them - kind of a catch-22.

In Florida, there have been dry joint failures as soon as 4 years, but that seems to be the exception. When I replaced mine at 7 years, there was a tiny amount of rust in one of the elbows, but it had not made it to the riser. That cut it closer than I intended.

Nobody can convince you if it makes sense to replace them. Only you can weigh the risk of a $2,000 elbow/riser/manifold replacement versus replacing an engine. Personally, I chose to replace the exhaust.
 
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Thanks for the feedback from everyone.

I’m going to error on the side of caution and go with new. I took a thorough look again and the manifolds look better then the risers as far as I can see, but from what I hear the rust in the manifolds tends to settle at the bottom and cause water flow problems. There is no protective coating left (not sure how long that lasts anyway) so everything has surface rust and some build up at the water ports. I would only feel comfortable using the old system if I had a machine shop boil out the parts. Then I would want to repaint everything to make it look nice and by that point it may only last me a few more years. At least I’ll have peace of mind with the new stuff and if I decide to trade up in a few years it will be a good selling point. If I keep the boat I should be good for another 10 years with an inspection in 5.
 
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Thanks for the feedback from everyone.

I’m going to error on the side of caution and go with new. I took a thorough look again and the manifolds look better then the risers as far as I can see, but from what I hear the rust in the manifolds tends to settle at the bottom and cause water flow problems. There is no protective coating left (not sure how long that lasts anyway) so everything has surface rust and some build up at the water ports. I would only feel comfortable using the old system if I had a machine shop boil out the parts. Then I would want to repaint everything to make it look nice and by that point it may only last me a few more years. At least I’ll have peace of mind with the new stuff and if I decide to trade up in a few years it will be a good selling point. If I keep the boat I should be good for another 10 years with an inspection in 5.
I think that is a wise decision. Hows the condition of your water heater? With the manifolds off you have room to check it and the pump and all other components. Great time for some general house cleaning while it's open if needed. Also check the flappers in the exhaust.
 
mine have lasted 10 year on my 190 SD with 4.3L... I plan on replacing them his summer...
 
I think that is a wise decision. Hows the condition of your water heater? With the manifolds off you have room to check it and the pump and all other components. Great time for some general house cleaning while it's open if needed. Also check the flappers in the exhaust.

The water heater was replaced in spring of 2010 and still looks good. I checked the flappers as you suggested and they look good too. One thing I want to see if I can get to is the starboard trim pump. It is tucked all the way in the back. The bracket is looking a bit rusted so I want to see if I can remove it and repaint.
 

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