Change Manifolds and Risers??

[sdleo26]

Hello all. My boat is an '04 290 Amberjack with 5.7L MPI MAG Horizons for power. The motors have 240 hrs, I am the 2nd owner in my fourth season. The delema I am having is whether or not to replace the risers (elbows) and manifolds. The boat runs at perfect temp (163 degrees) under load and 167 at idle. Has never creeped over the 4 seasons. There are no signs of leakage at risers (externally).

The system is a dry joint, which I understand is less probable to leak into exhaust and cause hydro lock as oppossed to a wet joint. I got prices ranging from $1700 (Aftermarket Mallory, Barr etc..) and $2500 (OEM) for parts, but struggle with replacing something that does not show ANY signs of corrison/leakage or overheat. I was thinking of cracking one riser and inspecting, but I would have to replace the gasket, correct?

I have researched this up and down. Most people replace, no two ways about it; every 5 years, and others claim to have 30 plus years on same manifolds and risers!!

Prior to opening it up, I was going to check for hot spots with temp gun. If I do not find any hot spots on manifolds and/or risers, I will not change and watch temp over time. First signs of creep I would change. I wanted to get thoughts on this approach, as I take maintenance very seriously.

Thanks for reading, this forum is an awesome place to get information!!

Best

Scott from Port Jefferson NY

 

[rcmafgny]

My vote is replace. I just had mine done. Different motor, but faced a similar situation and I waited... Tail end of last season got hydro locked. All good now, but PM is the way to go...

 

[1990-270-da-lover]

+1 on the above response, I just did mine because I found moisture on one of the plugs when I pulled them to replace. No outside indications of corrosion or rust. If they leak, they can cause serious damage to the internals on the engine, and the $ to replace will seem tame to the cost of engine replacement. JMHO

 

[sdleo26]

looks like I have a date with the bilge...

 

[Georgia SeaDawg]

Just do it! It looks like you are in salt water, and this is one of those items that you are happy when you replace them and find no damage. Can you squeeze out another year, possibly. BUT if you are wrong, that $2,500 bill can increase 5 fold.

 

[fwebster]

Most people let this go until the engine gets water in it. However, the truth of the matter is that this is a regular maintenance item. The manifolds don't corrode and die at the same time the risers do. As a general rule, with OEM castings, the risers are good for 3-5 years a salt environment. At the end of the 3rd season, buy a couple of gaskets and pop the risers off and have a look inside. If you do not have flaking rust, then clean the gasket surfaces and button the risers back up with new gaskets, and you have invested an 1-1/2 hours and bought another year's worth of piece of mind. Then repeat until you do see flaking rust and at that point, replace the risers. Every time the riser is off, you can visually inspect the exhaust passage into the manifold and look for flaking rust inside.

I have posted this before, but here it is again: The exhaust castings almost always fail from the outside in; not the inside out, meaning the rust action begins in the exhaust passages and rusts toward the water jackets, not from the water side out into the exhaust passage. The reason for this is because the exhaust passage is open to the ambient air around the boat 24/7/365 days a year. If you are in a salt water environment, then this air is usually very humid and laden with salty moisture. Then every time you start the engine, you heat up the risers and manifolds, only to cool them down at the end of the day or even several times a day. That expansion and contraction with heat causes rust particles to flake off in the exhaust passage and be expelled in the exhaust flow, thus exposing fresh metal to rust. The riser is the first exposed metal in the exhaust system that the sea air contacts, so the risers are the first to fail.

For the OP, I would have the risers removed and checked now, but I would not replace anything until you see the signs of impending failure inside the risers. Also, this has been a weak point on Mercruiser products, mostly with 7.4L engines but also with 5.0 and 5.7's as well and Mercruiser tries to improve product over time. I bet they have superceded the riser and manifold castings 25 times. You get the benefit of that product improvement when you buy OEM parts. Aftermarket castings don't seem to last nearly as long as Mercruiser ones. Don't be fooled by a warranty of X years on aftermarket parts either. If you get an early failure, you get water in an engine and are looking at a rebuild or valve job, the warranty will be prorated after the mfg examines the parts. This happened to me on a set of Barr risers and manifolds..........we broke them open at the end of year 2 just to check and found water in the passages; Barr prorated the 5 year warranty to 50% but it took them 12 weeks to make a decision and to tell us what they were going to do. I knew going in that I was done with Barr, so we immediately replaced the risers/manifolds with Mercruiser OEM parts and lost only 2 days on the water...but had I waited on Barr, I would have lost 3 months on the water and would probably have killed somebody at Barr. Some people have luck with aftermarket parts, I did not and would advise you to check them after the 2nd year if you use them.

 

[sdleo26]

Web, thanks, I think I will do as you suggest... What is "OP"?

 

[Irie308]

I'm truly terrified now. We just picked up our 2005 320 which was really well taken care of. The previous owner never did any work to the risers or manifold as he said he pickled the engines after every outing. I think we will have the risers removed and inspected at the end of this season.

 

[Quint4]

"OP" = original poster (person who started the thread)

 

[sdleo26]

got it, I need to brush up on the lexicon of forum acronyms!! Thanks again

 

[gerryb]

Been there...

Something else to consider...Not sure what you plan to do with the boat, but when we sold our 280 it needed new risers and manifolds. I didn't replace them when I had it but in effect paid for them to be replaced when I sold the boat. A knowledgeable buyer is going to certainly asked to have that credited towards the price they offer. IOW, your boat's value will be increased by the new manifolds/risers, unlike many other boat-related purchases. And you get the advantage of knowing that you are less likely to have a more catastrophic problem.

 

[sdleo26]

I just took the plunge; ordered 2 sets of OEM elbows and manifolds; $2603 delivered from Nuwave Marine. I could have saved another 200 if I picked it up, but not driving to south jersey to get them via LI. Best price I could find, they even beat Marineparts express, which is typically the lowest prices on parts. This is killing me, but the piece of mind is worth it I suppose... BOAT, Bust Out Another Thousand..... so so true

 

[BigJoeB]

I wish i read this sooner brotha, i picked up 2 sets of oem mans and risers for 649 per motor 5.7 delivered just a few months back brand new. So total was under 1300 and i installed

 

[sdleo26]

I wish i read this sooner brotha, i picked up 2 sets of oem mans and risers for 649 per motor 5.7 delivered just a few months back brand new. So total was under 1300 and i installed

I have dry joints, they are literally double the price. That said, when I crack open the elbows, I believe I am going to find the manifolds to be fine; they are FWC (i.e., have antifreeze in them) If thats the case, the manifolds are getting returned. It seems most people have different setups. If they were raw water cooled, then I obviously would need to be replace them. The more I read the more I find out. FWC closed system manifolds should last as long as the block from what I am understanding. Anyone have opinions?

 

[fwebster]

This is from post #6 above....the middle paragraph

"I have posted this before, but here it is again: The exhaust castings almost always fail from the outside in; not the inside out, meaning the rust action begins in the exhaust passages and rusts toward the water jackets, not from the water side out into the exhaust passage. The reason for this is because the exhaust passage is open to the ambient air around the boat 24/7/365 days a year. If you are in a salt water environment, then this air is usually very humid and laden with salty moisture. Then every time you start the engine, you heat up the risers and manifolds, only to cool them down at the end of the day or even several times a day. That expansion and contraction with heat causes rust particles to flake off in the exhaust passage and be expelled in the exhaust flow, thus exposing fresh metal to rust. The riser is the first exposed metal in the exhaust system that the sea air contacts, so the risers are the first to fail."

In other words, your manifolds are just as likely to be corroded because they corrode from the exhaust passage in; not the cooling side out. It doesn't matter if they are seawater cooled, jacket cooled or have Aunt Mamie's blackberry jam in them, they can still corrode and need to be checked every time you check the risers, but you don't need to replace them unless there is rust flaking off inside the manifold or the riser to manifold gasket surface is compromised. That is where most manifolds fail and it the only real reason you have an advantage with dry joints since yours cannot leak there.

 

[sdleo26]

This is from post #6 above....the middle paragraph

"I have posted this before, but here it is again: The exhaust castings almost always fail from the outside in; not the inside out, meaning the rust action begins in the exhaust passages and rusts toward the water jackets, not from the water side out into the exhaust passage. The reason for this is because the exhaust passage is open to the ambient air around the boat 24/7/365 days a year. If you are in a salt water environment, then this air is usually very humid and laden with salty moisture. Then every time you start the engine, you heat up the risers and manifolds, only to cool them down at the end of the day or even several times a day. That expansion and contraction with heat causes rust particles to flake off in the exhaust passage and be expelled in the exhaust flow, thus exposing fresh metal to rust. The riser is the first exposed metal in the exhaust system that the sea air contacts, so the risers are the first to fail."

In other words, your manifolds are just as likely to be corroded because they corrode from the exhaust passage in; not the cooling side out. It doesn't matter if they are seawater cooled, jacket cooled or have Aunt Mamie's blackberry jam in them, they can still corrode and need to be checked every time you check the risers, but you don't need to replace them unless there is rust flaking off inside the manifold or the riser to manifold gasket surface is compromised. That is where most manifolds fail and it the only real reason you have an advantage with dry joints since yours cannot leak there.

Frank, thanks. I was hoping you were going to reply. Appreciate the help; was pondering sending you an IM to verify what you just sent.

 

[BigJoeB]

I have dry joints, they are literally double the price. That said, when I crack open the elbows, I believe I am going to find the manifolds to be fine; they are FWC (i.e., have antifreeze in them) If thats the case, the manifolds are getting returned. It seems most people have different setups. If they were raw water cooled, then I obviously would need to be replace them. The more I read the more I find out. FWC closed system manifolds should last as long as the block from what I am understanding. Anyone have opinions?

Oh good for you, i guess i didnt read it through about the closed system and fwc. Good deal for you and good luck brotha

 

[sdleo26]

So I took Elbows off starboard engine; boy am I glad I am doing this; things were not so pretty, they would have failed any day... The question I have is where do I find the exhaust flappers?? Do I even have them on my setup (5.7 MAG MPI V DRIVE w/ dry joints )?? Should I replace those as well if I do have them? Any help would be greatly appreciated!!

Thanks
Scott

 

[OllieC]

So I took Elbows off starboard engine; boy am I glad I am doing this; things were not so pretty, they would have failed any day... The question I have is where do I find the exhaust flappers?? Do I even have them on my setup (5.7 MAG MPI V DRIVE w/ dry joints )?? Should I replace those as well if I do have them? Any help would be greatly appreciated!!

Thanks
Scott

The flappers on my boat are where the elbows/bellows meet the Y pipe that connects both port and starboard manifolds exhaust behind the engine - just before it is combined, and the exhaust is run out the transom. The flappers are suppose to keep the outside water out in case you stop to fast or are in reverse.

I'd like to see pictures of your manifolds. I have been debating replacing mine. Mine are Dry Joint as well and are showing some surface rust between the manifold and the riser.

FYI - when replacing gaskets, I was told before to not use the "green" gaskets because they have the potential to fail.

 

[sdleo26]

Thanks for the quick reply. I will post pics shortly. There are many different setups even for dry joint; I don't have risers, I just have an elbow that bolts down to manifold. The OEM gasket for that is metal. In my setup (closed cooling) I have the two outside passages blocked on gasket. I will post a pick if that as well. If you have closed cooing, you would use same gasket.