When to replace risers and manifolds in fresh water?-gctid368583

[Guest]

Hi everyone!

I have done a search and can't seem to get a good answer. I keep my 2001 Ciera in the Mississippi for 6 months a year. The boat has always been in fresh water. So my question is how long will these last before they need replacing. I just got a magazine from BoatUS and it had an article that kind of rattled me about the longevity of risers.

Scott

[Four_Pyrates]

20 plus years. Salt water only 3 years. If you have it out 6 months a year, I'm sure you would be winterizing with 100% antifreeze. That stops any rusting.

[boatworkfl]

You can remove the exhaust hose and check for rust at the water outlet area.

[carguy]

Hey fellow Kings dweller, didn't know you were on this board. Unless we get some rain this year, you wont have to worry about your risers as we wont be able to get out of the slips.

[Guest]

On my 2855 I took them off at about 10 years and they were fine. I wouldn't be surprised if they lasted another 10 years. It spent most of its life on the Mississippi pool 26.

[MidnightSun]

I have not heard of anyone replacing these unless it was a previous salt water boat. To answer your question of when to replace? I would say never as the engine will wear out before they do. Gotta love fresh water.

[smitty477]

"I just got a magazine from BoatUS and it had an article that kind of rattled me about the longevity of risers."

Boat US article with service life % is cut and pasted below.

Practically speaking from 'salty' northeast experiences over 30 years and dozens of boats the policy is typically dissasemble & inspect at 5-6 years and replace at 7-9 years. Certanly a bit longer for heavier diesel applications but mostly on target for typical 8 cylinder gas applications. Just finished helping a few friends do this over over this past winter on a 37 Sea Ray, 31 Sea Ray and a Jersey (all gas).

Hope this helps

Exhaust Manifolds

Exhaust manifolds last forever, don't they? Even if they do fail, it isn't a major problem, right? These are common reactions when people are asked about their boat's manifold. Unfortunately, exhaust manifolds are important, and ignoring them can potentially lead to expensive problems, perhaps an engine rebuild. There is an additional hassle-manifolds are normally damaged by corrosion, so they're not covered by your insurance policy.

All of this makes the outlook seem rather bleak. It's not as bad as it seems, though. All that's needed is a change in attitude. Rather than seeing it as a "sealed for life" component, view a manifold as a service item to be replaced at regular intervals. If you do this, major problems can be avoided.

Life Expectancy

How long will a manifold last? Obviously the way you use your boat will be a factor, as will the type of water it's on. Saltwater boats are going to see a shorter manifold life when compared to their freshwater counterparts. Most experts suggest that a manifold will have a life expectancy of six to eight years. However, heavy use in saltwater can see this drop to as low as three years, while lightly used freshwater boats can get up to 20 years out of a manifold. One thing is for certain, the older your manifold gets, the more likely it is to fail. This is clearly shown in the chart below.

Years in Service Probability of Failure

3 0.5%

4 25%

5 45%

6 65%

7 85%

8 90%

9+ 100%

Why So Fragile?

The manifold is a complex metal casting, actually a pipe within a pipe. It feeds hot exhaust gases and water to the riser where the gases and water combine to continue their trip overboard. Without the cooling effect of the water, the hot gas would burn through a hose or thin wall pipe very quickly. Keeping the water and gases separate in the manifold is critical. If water finds its way into the gas-only section, it can enter the engine cylinders and wreak havoc with the internal engine parts.

Manifolds and risers live in an incredibly harsh environment. They endure very hot corrosive gases slamming into the manifold at high velocity. The water jacket portion of a manifold is intermittently exposed to hot saltwater and moist air, the perfect conditions for corrosion. All the time they're vibrating madly during running time and left idle for long periods, allowing rust to eat away at the metal. That they last as long as they do is impressive.

Symptoms

Before your manifold fails, you may get warning signals. Needless to say, you should take notice immediately. If your engine is difficult to start, produces white smoke, or runs roughly, water in the cylinders may be the culprit. If you ignore the situation, hydrolock may occur. This is when sufficient water has leaked into the cylinder that piston compression becomes impossible. Massive, and usually terminal, damage will result as you try to start the motor.

Inspection is always a good idea, and we recommend that you try to do so at least every two to four years. It may seem a little pointless since it's impossible to see into all the passages, but you will still get some clues about the extent of any corrosion. Your manifold may be blocked with the products of corrosion, for example, leading to "hot spots" in the cooling system and low-level overheating. These won't necessarily show up on your temperature gauge, but can result in a shortened engine life.

If your boat suffers more than average corrosion problems, then it may be more likely to suffer from premature manifold failure. Stray current corrosion is evidenced by rapid zinc wastage, corroding lower units and corrosion build-up on through-hull fittings. This is normally the result of poorly installed 12vDC wiring or faulty 12vDC equipment. Electrical problems should be corrected as soon as possible; the damage caused by leaky 12vDC wiring is potentially far worse than a broken manifold.

Manifold Replacement

Replacing a manifold is certainly a job that you can do yourself. It may take longer than you expect, though. Bolts may be rusted in place and other fittings may be in your way. It can turn out to be a day-long job. If this does not appeal to you, boatyards will tackle the job for you.

If you decide that your manifolds and risers are nearing the end of their service, and you don't want to interrupt the boating season with a blown engine, replacements are available from by calling the BoatU.S. Engine Parts Specialists at 800-528-4828. You will need the make, model and serial number of the engine, the exhaust pipe diameter, and will need to order the necessary gasket kit, installation kit, and end plates if required.

A final word of warning: each year, owners (and mechanics) sink boats by leaving the exhaust ports unplugged after disconnecting the manifolds. Waves sloshing into the ports can sink a boat overnight. Hoses must be plugged and tied securely above the waterline to prevent water from flowing into the boat. With this in mind, consideration for your manifold will pay dividends in reliability and peace of mind, giving you seasons of trouble-free service.

[Guest]

The life of a freshwater manifold lies in the winterizing. Most failures are from freezing.

I know people who just run their outdrive in a tub of antifreeze. This does not do a good job and I am afraid many marinas do not do a good job of winterizing as well.

I remove all hoses and drain plugs completely. Run a wire up the drain holes to make sure they are not blocked.

After draining I put 50/50 antifreeze back in the block and oil cooler. (this needs to be properly drained in the spring to insure it doesn't get into the water)

I would recommend changing the exhaust and riser gaskets every 5-7 years. (this can be done on the boat in most cases)

[MidnightSun]

check737 wrote:
The life of a freshwater manifold lies in the winterizing. Most failures are from freezing.

I know people who just run their outdrive in a tub of antifreeze. This does not do a good job and I am afraid many marinas do not do a good job of winterizing as well.

I remove all hoses and drain plugs completely. Run a wire up the drain holes to make sure they are not blocked.

After draining I put 50/50 antifreeze back in the block and oil cooler. (this needs to be properly drained in the spring to insure it doesn't get into the water)

I would recommend changing the exhaust and riser gaskets every 5-7 years. (this can be done on the boat in most cases)

Not actually true however antifreeze addition will help although I question the need as a rust inhibitor. We normally winterize with the drain only method. My previous 2855 I sold to my dock neighbour many years ago, he sold it two years ago with around 1800hrs on the clock, risers, gaskets, manifolds all original and actually from the outside still looks brand new after 20 years. It is still going strong the last I heard of it. About the only thing really needing replacement IMHO are the bellows on a 5-7year plan.

[Guest]

I do all my own winterizing, I did the Merc antifreeze method for years , but now I just drain and clean out the orfices with a wire and refill with the pink just to make sure I got into all the spaces, and then drain that off. The block is empty all winter. I have never had a problem, but Like I say, the article above kinda rattled me a bit.

Scott

[6104696]

FYI I have a 2005 Merc 6.2 with a Bravo 3. Used extensively in saltwater, but flushed with fresh water (10-15 minutes on the muffs) after every use or after every weekend of use. Also a 2007 Merc 135 hp with an alpha drive.

No problems thus far. Same has been true for 2 previous stern drives that were similarly maintained and used for 7-9 seasons of ownership. Sooooo....my poiint is that if you have the opportunity to regularly flush your saltwater-used stern drives, you can greatly reduce corrosion issues.

(I also keep the engine and accessible oxidizable parts coated in a good corrosion inhibitor).

[Guest]

would these ceramic coated ones be any better ?

http://www.perfprotech.com/store/articles/marine-exhaust.aspx

[itsabowtime2]

In fresh water they really should never need replacing unless they crack from improper winterizing. Mine are 19 years old and going strong.