Exhaust manifolds

Barlow1016

Member
Jun 3, 2017
45
Farmington Utah
Boat Info
1999 340 Sundancer
Engines
454 merCruiser 7.4 MPI Bravo one outdrive’s 4 blade props. 5.0 Westerbeke generator
I have a 1999 340 Sundancer 7.4 MPI with bravo one outdrive’s fresh water boat. I was hoping somebody could chime in and direct me to the proper OEM exhaust manifolds for this fine boat?Thank you gentlemen
 
WOW, those are less than HALF the price of 8.1 manifolds!!!!
Did you replace just for piece of mind or were they starting to leak. Mine show no sighs of leaks or wear but i have no idea how old they are so i think i am just gong to replace them in the spring. Where did you buy yours at?
 
Did you replace just for piece of mind or were they starting to leak. Mine show no sighs of leaks or wear but i have no idea how old they are so i think i am just gong to replace them in the spring. Where did you buy yours at?

Michael, pretty much for peace of mind. I have no idea how old they are. I think I've heard that they last around five years in saltwater. Also, I don't think you get much (if any) notification signs when they do go bad. (But I may be wrong.)

I wish I had a big band saw and could slice them in half to get a feel for the construction and try to determine HOW they might go bad. If it was a matter of the water passages just getting filled with corrosion so that monitoring heat and water flow could give you an indication they were dying, that would be good. But I know nothing kills a boat motor faster (and more often) than seawater in the engine oil.

Does anybody here on CSR know how these 8.1 manifolds age out?

I purchased the "Manifold water rail conversion" kit - 866178A02 which includes the manifold along with new drain elbows, sensor, bolts, turbulator and gasket. Got them from Offshore Performance Specialties. (Which I found on Ebay, but called them directly and got the same deal.)

I also just pulled the trigger on new stainless risers from Nuwave marine, a good price (as far as the going rate, but they aint cheep!) and free shipping via Fedex. Rumor is that they don't last forever either, even though they are stainless. And they tend to weep water down into the manifold when they begin to corrode through.

So, for more money than I paid for my entire last boat, I have a new exhaust system!!!
 
I have a 1999 340 Sundancer 7.4 MPI with bravo one outdrive’s fresh water boat. I was hoping somebody could chime in and direct me to the proper OEM exhaust manifolds for this fine boat?Thank you gentlemen

Is someone recommending you do this? Has this boat always been in freshwater? The likelihood of a 100% freshwater boat needing new risers and manifolds is very low - almost non existent. I have boated in freshwater my whole life, I never hear of anyone replacing a riser or manifold as a maintenance item like you do in salt water. Other things happen, they freeze, crack etc, but never rust or corrode like salt water. It won't hurt to change them, but I bet if you pull the risers you will find they are like new.
 
Michael, pretty much for peace of mind. I have no idea how old they are. I think I've heard that they last around five years in saltwater. Also, I don't think you get much (if any) notification signs when they do go bad. (But I may be wrong.)

I wish I had a big band saw and could slice them in half to get a feel for the construction and try to determine HOW they might go bad. If it was a matter of the water passages just getting filled with corrosion so that monitoring heat and water flow could give you an indication they were dying, that would be good. But I know nothing kills a boat motor faster (and more often) than seawater in the engine oil.

Does anybody here on CSR know how these 8.1 manifolds age out?

I purchased the "Manifold water rail conversion" kit - 866178A02 which includes the manifold along with new drain elbows, sensor, bolts, turbulator and gasket. Got them from Offshore Performance Specialties. (Which I found on Ebay, but called them directly and got the same deal.)

I also just pulled the trigger on new stainless risers from Nuwave marine, a good price (as far as the going rate, but they aint cheep!) and free shipping via Fedex. Rumor is that they don't last forever either, even though they are stainless. And they tend to weep water down into the manifold when they begin to corrode through.

So, for more money than I paid for my entire last boat, I have a new exhaust system!!!
Here is a cross section of the manifold, (riser not shown)and elbow.

turbulator4-copy-300x208-300x208.jpg
-Kevin
 
On my port engine and on the port side, I Sometimes get little spray. Sometimes it does it sometimes it doesn’t. I’m assuming that the exhaust manifold has a small crack in it so…I will replace the exhaust manifolds.I would imagine the risers are probably just fine. Yes it’s always been a freshwater boat
 
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I started marking larger parts that I install on my boat. Both for me and also any possible future owner. Now there is no guessing as to when those manifolds (water pump. transmission cooler, risers, etc.) were replaced last.

IMG_5156 by David Orwig, on Flickr
 
Good idea. I keep a log and associated receipts in a binder. I handed off a binder to the guy who bought my old boat and he really appreciated it. It included instructions, intervals, part numbers and sources for all regular maintenance items.
 
Do they still make the ceramic coated ones? I remember they were having problems with the coating detaching in big pieces.
 
Do they still make the ceramic coated ones? I remember they were having problems with the coating detaching in big pieces.
Just bought a set, mani's, and elbows $1500 no hardware . Quoted $950 same place for the E-coat
 
I boat in saltwater and am on my fourth set of manifolds and risers. I've tried after market, e-coat and a few different brands. OEM costs more but so far has lasted the longest. I had one set that rusted out after three seasons! Fresh water boats though usually last as long as the engine. I don't know that for a fact but I've been told that by more than one person.
 
I kind of look at it this way. An airplane without maintenance records is 100% worthless. A boat without maintenance records is worth less. Don’t ever skimp on maintenance or parts and keep a log in a manila file so when you want to sell your boat everything is documented.
 
M Prod, What else can you councel me on to purchase while I am purchasing these OEM exhaust manifolds and risers? Probably purchase all new hardware? Also what about any thing else that comes to mind? Thanks for your time man
 

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