Replace risers/manifolds?

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interj

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I'm sure the answer depends... But would like to hear from some others experience.

99 boat with twin 4.3 mercs, just under 500 hrs. Used in salt water on long island and docked in brackish on a freshwater creek. Coming up on time for replacing the risers and manifolds. They were last done in 07 I believe. Just received a quote for ~1300 per engine.

The engines have always been maintained , I have had the boat for the last 10 years. They are not showing any signs of wear. Do I replace th risers 1 more time ? How much life can be left in these 14 year old engines ? Or save the money for rebuilds / new engines ?? Opinions are welcomed.
 
The only way to check manifolds and risers for wear is to remove them and to examine their interiors; but even that isn't any guarantee that no leaks will develop. All you need is one rust-through and you've got problems. That said, 500 hours on them with a mixture of salt and brackish water is not a death sentence for the manifolds. As I read it, you've had the manifolds and risers done once already, so they have less than 500 hours on them. If it were my boat, I'd pull the risers and manifolds. If they really looked as good inside as they do outside, I'd probably leave them. By the way, you could still have another 10 years or so on those engines. A great deal depends on how well they were maintained, so don't jump to the conclusion that they'll automatically need to be replaced soon. Good luck. Hy
 
Whenever you replace or rebuilt the engines (which indeed should have entry of life left esp if FWC) you will have to redo the risers anyway.

6 years old risers in salt water? Yeah the brackish water helps. If there is no sign of rusts outside I'd squeeze another year but if you see any evidence of rust streaks outside means the inside is probably started to have issues.
 
I replace my risers/manifolds every two years religiously. 1,300/engine is stupid, especially for such a basic DIY project. If you can use a wrench, you can do this job.
 
Safe to assume the 1300/engine is parts and labor?
 
You didn't say if the engines were FWC or RWC. If a full FWC engine, then the manifolds should last the life of the engine.
 
RWC - and yes parts and labor.

$1,300 is original Merc parts, was told I can save about 200 going after market parts.
 
Sounds about right. You are several yrs past due already. Should still have a lot of life left to the engines at only 500 hrs.
 
I am not sure what you are looking at, as far as access, but on my engine, it took me about 3 hours, to remove and replace the manifolds and risers. Merc 305. If I remember right it was around $600 for the Manifolds and risers and gaskets. Next time I will not do it in the middle of August!

What you may want to do, is get a wrench on each bolt on the manifold, and see if they will turn, before you commit to doing the job yourself. If one or more are forzen, you may want to pass on the job. (Once you loosen do not run until you replace everything!)

One thing I found that made the job a lot easier, was studs for the exhaust manifold. They are held in with bolts, but to start I used two studs where the outer most bolts go. Put the studs in finger tight, put the gasket in place, put the two inner bolts in place, the replace the studs with bolts. It makes lining up and placeing the manifold 10 times easier.
 
I'm not familiar with you area but a friend kept his 302(ford/RWC) engine in the waters in S.F. Bay. She lasted about 7 years before the block rusted thru. The boat was supposedly kept in fresh water prior to his purchase.

14 years in even brackish waters is problem. What's the water temp. Warmer the water, the faster corrosion acts.

I'd run it til she dies and replace with new engines. Check prices between 4.3 and 5.7
 
If you are going to do it yourself, get a can of liquid wrench and wet down all the bolts a day or two before doing the work. Even run the engines as the vibrations will help the liquid soak even further down the bolt threads. Can't hurt and it might help make things a whole lot easier.
 
I just replaced the elbows on my big blocks. I found Permatex Freeze & Release to be a life/ball saver. It uses liquid nitrogen to freezes the bolt to shrink it and make it easier to break loose a corroded/stuck bolt. It worked on all but 2 of my elbow bolts which I ended up having to cut off.
 
You guys have me worried! Our '96 SBC is RWC and has run 1300 hours in FL's warm salty water.
 
Ewwww, John, maybe do a test. Pop a freeze plug and give the block an inspection.

FYI. Anyone doing their own work, use permatex aviation gasket sealer on all threads. It not only acts as a thread locker, it seals out any water which prevents the bolts from getting frozen.
 
AMEN to the Sealer! I used to use Never-Seez, but a watertight seal keeps the salt away by keeping the water out. That "Corrosion" is more of a Salt Deposit.
 
Of course its hard to say, but I have kept my boat in salt water for 11 seasons worth on the North Shore, when I got the boat it was already 14 years old. It came from a freshwater region but had already been used here for some time because it came with several coats of bottom paint on it. I replaced the OE manifolds in 2004. In 2010 I replaced them again, and found that the water outlets in the riser area (OMC one piece batwings) was starting to clog, but no sign of rust through. So now the engine is 25 years old and still runs as it always has, no sign of rust through yet. I have looked in the intake manifold when I replaced the thermostat (every few years) no sign of flaking rust, and I looked in the block water passages when I replaced the front water pump, same thing, no flaking rust. So while risers and manifolds can rust through in less than 10 years in salt water, the block it self is likely to last longer. I have always filled the engine and manifolds with the best -100 antifreeze when I winterize to keep air out (that and the corrosion inhibitors reduce corrosion). So to answer your question, if you can do the job yourself, its is worth replacing them and keep running the engine. If you liked the boat enough to repower I'd do closed cooling but for now, doing the manifolds is not that bad of a job if you can get the bolts out. On my OMC one thing they did that really helped, was use plated studs in the block, with plated nuts. I can pull those manifolds off in about 15 min. Spray the area below and around the rubber hose with silicone spray, spray some PB Blaster or Kroil on the nuts/studs, I let it sit for a few hrs and they come right off. I like the use of studs/nuts much better than bolts. If you have to use bolts, though, I'd use something like OMC gasket sealer to make em come out easy next time. I use it on thermostat bolts and they come right out.
 
General consensus for RWC engines is replace manifolds and riser/elbows every 3-5 years. Granted , a lot of people do keep them longer, sometimes much longer (& sometimes damage in less time), with no issues, but the concept of "preventative maintenance" is replace BEFORE engine replacement or iffy-outcome major rebuild is required due to leaks that could have been avoided.

If the engines and transmissions or drives are apparently strong and in good shape , the $1300 for replacement parts and labor sounds like a good deal to me and good value. . It might cost you that much or more if you do it yourself, plus potential knuckle skin & frustration factor if they prove to be reluctant. 500 hrs. sounds like very little, but as they say, "corrosion never sleeps."

That said, shiny new engines & transmissions or drives will make you feel good and may have more power and other improvements (FWC?) if the irretrievable cost does not put you off.
 
Sany,

I presume that you meant to say every 3 to 5 years, not "every 35" years.

I recently replaced mine after 6 years. Inspecting them after removal showed almost no thinning of the walls and only a little blockage of passges (that could proabably have been cleaned out). But I broke a couple of bolts in the manifolds and already had the new parts on hand, so I replaced all of them anyway.

Mike
 
quote:
Originally posted by meide

Sany,

I presume that you meant to say every 3 to 5 years, not "every 35" years.

I recently replaced mine after 6 years. Inspecting them after removal showed almost no thinning of the walls and only a little blockage of passges (that could proabably have been cleaned out). But I broke a couple of bolts in the manifolds and already had the new parts on hand, so I replaced all of them anyway.

Mike

Click to expand...


Ye-es indeed, Mike, I did mean 3-5 yrs. Thanks for the correction of that blatant typo! 35 yrs could really be bucking the odds a scosh unless the boat sat on the new-showroom floor that long or only ran in Lake WD40. But I suspect there have been a few FW-use-only boats' cast exhaust parts that have survived that.

Not all castings by the same mfgr. come out of the mold with equal quality, so that is another factor that can affect the longevity.
 
Just to point out, all this talk about replacing risers / manifolds, we are talking about salt water only? I've always boated in freshwater lakes - I have never replaced an exhausted manifold or even pulled a riser to inspect. It's just not even an issue - manifolds last the life of the engine.
 
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