How often do you replace manifolds and risers?

C

chazaroo

New Member
Dec 4, 2006
415
Florida
Boat Info
1996 Sundancer 250
Engines
single 5.7 w Bravo III
This is mainly a salt water question. I'm curious to know how long these things last on average. Secondarily how often do you re-torque risers?
 
Usually about 4 years.

I re-torque everything before spring launch.
 
sounds about right. After 3-4 years pull a riser and inspect. Look for early leaking sign always though. (hard starts,leaking gaskets, WOT the temp increases, white smoke etc.


Mine lasted 9 years in New England(salt water but only 260 hours) they still show no signs but it's time to just replace everything
 
I bought my 2000 260DA over the summer with 140 hours and all original manifolds / risers, etc. There are no signs of trouble, but I'm having them replaced this winter to be safe.
 
Please use caution in accepting anyone else's experience as a standard for riser/manifold life. There are far too many variables involved for any one answer to be right.

I've seen Florida (we boat 12 months a year) OEM risers last 6 years and aftermarket ones to last only one full season. Do you boat 12 months, are you in brackish or salt water, do you use your boat regularly or does it sit idle for weeks at a time, do you freshwater flush after use, etc., etc.

Furthermore, keep in mind that the riser to manifold gasket, not the riser itself, is what usually leaks and causes the problem. Furthermore, the risers are significantly more likely to leak than the manifolds are and that that if the riser to manifold gasket is maintained and checked/replaced regularly, the manifolds hardly ever fail.

The best approach, and the one that will save more engines than you might imagine, is to religiously remove the risers and check then which necessitates replacing the gaskets frequently. I did it annually when we had a Mercruiser powered 390EC.
 
I agree with Frank. What aftermarket risers were you referring to that failed in 1 season?
 
Every Jan, 2008, and never before in my 15+ years of Merc ownership. 1st boat - 5.0 Liter with alpha for 4 years - Absolutely zero maintenance required other than fluids (lakes + trailer). 2nd boat, 1997 SR250 with 5.7L, BIII, and SS risers - 10 years, ocean + trailer - pulled manif/risers almost every year. 3rd boat '05 340 w/ 8.1S - 3.5years - aluminum manifolds, ocean + slip - new manifolds this month (starting today).
 
I agree that an annual check is a good idea. And the gaskets are the problem most of the time from what I've heard. Also, the idea of periodically retorquing the riser bolts to spec may go a long way to solving the problems, according to my mechanic.
 
I understand that due to the caustic nature of salt water, risers/manifolds/gaskets will require a frequent maintenance schedule.

That being said, what should I be looking at with a fresh water boat.

The boat is 23 years old, I am the third owner, approx. 775 hrs., some years stored in water, some out (last year in water). I'm not sure if they have ever been replaced. Is this something I should be concerned about?

thank you all!
 
No question they last longer in fresh water. Having said that, it's important to check them periodii\cally. And 775 hours is way overdue for at least a check. When you pull the risers you'll be able to see the condition. Whether you do it or have your mechanic do it, it isn't a huge deal, though in your case the bolts may be tough getting off. But any way you cut it, risers are cheaper than a new motor, which is what you'll need if the risers or manifolds or gaskets fail.
 
ghuskin said:
I understand that due to the caustic nature of salt water, risers/manifolds/gaskets will require a frequent maintenance schedule.

That being said, what should I be looking at with a fresh water boat.

The boat is 23 years old, I am the third owner, approx. 775 hrs., some years stored in water, some out (last year in water). I'm not sure if they have ever been replaced. Is this something I should be concerned about?

thank you all!
Click to expand...

Dude!
 
Watch out for OEM manifolds leaking from the water jacket into the exhaust chamber. This can cause water to get into the combustion chambers when the engine is shut down- BAD NEWS! 3-4 years in salt water is about right, but the best idea is to flush, flush and flush some more with fresh water. An even better idea is to install a heat exchanger and use antifreeze. Then all there is to worry about is the riser.
 
Chazaroo,

Thank you! I'll keep a close eye on things!

Hampton,

Dude? What is this supposed to mean? This is my first boat and am glad of the great resources here (all expressed on another thread). I confess that I don't know as much as many of you, mostly on experience alone. this is why I asked the question. I feel it's better to ask a stupid question (to some) than to not ask at all, only to regret that i didn't later on.

My mechanic did not indicate anything suspicious the when the boat was in for outdrive repair inthe summer. they gave the engine look, and didn't say anything bad (they would have said something if it was wrong).
 
GHuskin,

No offense intended at all. There's a series of commercials shown during football games where it demonstrates the 100's of different uses of the word, "Dude." This one is along the lines of, yes, it's a good time to get them checked. It doesn't mean that you were delinquent, but I certainly think it's time.

Dude (signature block)
 
Hampton,

This will definately be on my list! sorry I didn't catch the reference. Makes much more sense now!

While on the subject, what signs do I need to look for when inspecting the risers/manifolds/gaskets? rust? leaking? Is there any way of finding out if they are original or not? if everything looks o.k., should i at least change the gasket?
 
Ghuskin,

I have a similar situation, I purchased my boat (1983 245DA) late in the fall of 06, it's got a bit less than 500 hours on it, was wet slipped in 06 in fresh water but on the trailer since. I'm at least the third owner and I will be pulling my risers off to check for the first time this spring. Not being around saltwater (in small boats at least), I'd never heard of the corrosion problems with the risers and manifolds. I've asked boaters around here and it's not uncommon to go many years without problems...

Now I hope I can get those bolts off OK...
 
GH,

I'm not an expert, but I believe that you need to have them pulled and inspected by a Merc Technician, or equivalent, since it has been so long. Once you have a starting point, you can keep an eye on them yourself between maintenance periods, but then you may still decide to have them pulled annually. From reading others' posts, it may pay to have them pulled every year to keep fresh gaskets on them and to keep them torqued correctly. This could save you some good life on all the parts, especially the engines.
 
I totally agree with Hampton. Have a Merc technician pull the risers and check everything out. Then you've got a benchmark to start from and a plan for how often you should be checking.
 
fwebster said:
Please use caution in accepting anyone else's experience as a standard for riser/manifold life. There are far too many variables involved for any one answer to be right.

I've seen Florida (we boat 12 months a year) OEM risers last 6 years and aftermarket ones to last only one full season. Do you boat 12 months, are you in brackish or salt water, do you use your boat regularly or does it sit idle for weeks at a time, do you freshwater flush after use, etc., etc.

Furthermore, keep in mind that the riser to manifold gasket, not the riser itself, is what usually leaks and causes the problem. Furthermore, the risers are significantly more likely to leak than the manifolds are and that that if the riser to manifold gasket is maintained and checked/replaced regularly, the manifolds hardly ever fail.

The best approach, and the one that will save more engines than you might imagine, is to religiously remove the risers and check then which necessitates replacing the gaskets frequently. I did it annually when we had a Mercruiser powered 390EC.
Click to expand...


I have a 350 FWC block (6 years 250 hours - very low). What should I check for after pulling the risers?
 
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