Service life of manifolds and risers

[Mullet]

Hi All,

I was recently on a trip to some offshore islands here in Oz and my engine over heated. Turned out is was due to blocked water passages in the risers. I took them off and soaked in acid which cleared the blockage but also removed a lot of flaky material as well. Through my research it seems that the manifolds and risers are pretty much consumable and fail with relatively little warning signs resulting in major engine damage. As a result I am almost to the point of replacing the manifolds and risers with these (http://www.hitekmarine.com.au/). However, another CSR member suggested I should wait and see if the manifolds and risers really need replacing before I do anything. So before I bite the bullet I thought I would ask if anyone one here knows if there is a more “scientific” approach to determine if the manifolds and risers really need replacing other than waiting for hydrolock:grin:.

For info the engine in questions is a raw water cooled Mercruiser 5.0L MPI with dry joint exhausts operated in salt water.

Cheers
Toby

 

[Nehalennia]

HiTeks are a great alternative I think although spendy. I believe they are made in your area though which may save some shipping cost. I replaced mine with Merc replacements last spring. I elected to switch up to the new dry joint style.

 

[Mullet]

Hi Nehalennia,

Yeah they are a bit expensive at $2500 but I also have the dry joint manifolds and risers and I have been quoted $1900 for replacements over here and so with the extended warranty and life (claimed) I am pretty sure which way I go.

However, as you can see neither option is cheap and so I was hoping to get the most of my current ones. I know that I might be penny wise pound foolish if the old ones cause engine damage but it still doesn’t make it easy to part with my 2 grand

Cheers

 

[IanBat]

Hi Toby,

Barneyridge on the forum, here in Sydney, got a set o the hiteks, about 6 weeks or so ago, not sure if he has fitted them yet.

The advice I was given by a friend who is a marine engine dealer (and PO of my boat) is the OE manifolds should last me around 6-8 years or more. However he did recommend I have the gaskets replaced every 2 years and inspect manifolds


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[kaz911]

my personal take is - if you don't flush in salt-water - 3-4 years - if you flush well - 4-7 years - if you have 1/2 fresh water cooled system - 5-10 years. But there are no rules really - that is why I always get mine inspected annually - but I'm in VERY salty water. Twice pr year might be fine in not so salty water.

 

[dicor]

my personal take is - if you don't flush in salt-water - 3-4 years - if you flush well - 4-7 years - if you have 1/2 fresh water cooled system - 5-10 years. But there are no rules really - that is why I always get mine inspected annually - but I'm in VERY salty water. Twice pr year might be fine in not so salty water.

That's about right IMO (Although I think the last part is a typo). I installed a Volvo Neutra salt system on my Bravo3. Went right on, no big deal. Now before I shut the engine down I induce a salt neutralizer into the raw water system it can't hurt and anything I can do to prevent having to replace that 454 I'll do.

 

[rcknecht]

The length of life depends on sality, water temp, length of your season, and if you flush with fresh water or not. pulling a riser once year after about the forth year of service is not a bad idea. HiTek would be a good option, since you can talk to Allen directly. They are manufactured in China, so you will have shipping costs. I have had some gasket issues with my HiTek manifolds, but overall I like them, and Allen stand behind his products.

Bottom line, is inspect them and replace them before they fail...

 

[Mullet]

Thanks for all the replys. It has been a real shock for me going to an I/O from outboards and I guess I was just surprised to find out about the manifolds being a maintance item with such a short life. I do like the tub though so I think I will just buy the hi tel ones tomorrow as I certainly don't want to spend $250 on gaskets every year to inspect my current ones. Thanks again.

 

[kaz911]

That's about right IMO (Although I think the last part is a typo). I installed a Volvo Neutra salt system on my Bravo3. Went right on, no big deal. Now before I shut the engine down I induce a salt neutralizer into the raw water system it can't hurt and anything I can do to prevent having to replace that 454 I'll do.

Yes - meant every two years sorry

 

[MarkIC]

Did you see any significant economy or WOT rpm increase with the HiTek like they claim?

 

[bjdunnie]

Certainly worth keeping an eye on.

I have just rebuilt an engine after a manifold failed which cost $$$ Sadly the failure occurred 2 weeks before the boat was due to be lifted and both sets of risers and manifolds replaced.

Both engines (5.0l Mercs) had original manifolds and I bought the boat in December knowing that they needed to be changed. When removed, Port engine was not too bad, with some corrosion within the the risers (ok for 10 years of service) and still very servicable. Starboard was a mess and we suspect that it had been leaking water into the engine for some time.

I plan to inspect every 2 years, and budget to replace every 5-6 years when operating in salt water.

 

[julians]

The general consensus on dry joint manifolds is to replace when the water passages get blocked, so yours seem about ready for replacement.

The usual mode on failure for the wet joint manifolds was that that gasket sealing surface between manifold and riser would become corroded and let water from the cooling passages enter the cylinders,but this cant happen on the dry joint manifolds.

The other mode of failure was that the wall between the colling passages and the exhaust passages woukd corrode and become so thin, it would crack and let water enter the engine. This was a much rarer occurance in the wet joint manifolds because the gasket surface would fail way before the walls became too thin.

The dry joint manifolds are far superior to the wet joint manifolds and eliminate a significant cause of engine hydrolocking(ie the first mode of failure), and as a result should last longer, and give warnings of a problem ( ie overheat).

A lot of people dont distinguish between wet joint manifolds and dry joint, and a lot of the scare stories you read about are related to the wet joint manifolds ,which were a poor design.