Manifold Replacement

[Jake007]

So I had my boat in the shop for repairs to the PS cylinder and a bad water pump... cha ching.... They had to remove the Starboard side exhaust manifold for access. This manifold showed signs of corrosion and reduced passages. My boat is 14 years old and I run some salt water and some fresh but always with a good engine flush after salt runs. I did not have the manifolds replaced now to spread out the cost of all these repairs.

Q. What is the usual lifecycle for manifold needing to be replaced under the conditions stated above?
Q. If the engine is still running cool, how long can I reasonably go before replacing my manlifolds?
Q. What is the danger of not replaceing them now as long as the engine cooling still shows good.

 

[tpenfield]

Re: Manifold Replacement

the issue is not so much about cooling as it is about leaking from the water passages into the exhaust side and eventually into to valves/cylinders.

 

[Jake007]

Re: Manifold Replacement

OK, so it sounds like it is best to change at the recommended interval. So what is the normal expected life of the manifolds.

 

[Don S]

Re: Manifold Replacement

There is no "Normal" time period they go away. Depends on how much you use it, how long it sits unused without being flushed. How often and long it's flushed, and even if something like Salt Away is used.

Basic rule of thumb, they last 5 to 10 years. But there are exceptions both ways.

Best thing to do, is if everything is working fine at 5 years, remove the elbows and inspect for gasket surface erosion around the water passages of the manifold and elbow.
Don't clean them out, when they get plugged up, that tells you they are at the end of their life, the next thing you find is salt water in your engine and you get to go searching for a new engine.

 

[aerobat]

Re: Manifold Replacement

i think in any case its time to replace immediately when the exhaust screens in the cylinderhead are not black but sho up signs of rust/water . then the manifold already started to leak.

the bad thing about it when i understand it right is the case you may not notice a manifold that starts to leak . it will leak slowly into the exhaust valve and corrode it more and more out until some day you engine will drop the exhaust valve. and there will be no signs in engine roughness or temperature.

 

[Jake007]

Re: Manifold Replacement

Well thanks again for the knowledge. I will bite the bullet and plan to get'em changed out in the next month or so. I suspect that the bolts on the manifolds (14 yrs) are the type that are frozen in place with rust and not worth trying to do myself?

 

[Jake007]

Re: Manifold Replacement

So a follow-up question. I am trying to get a feel for how big of a job it is to change these manifolds and if I should try to tackle it myself. I generally only do the basics: tune up, hoses, belts, oil, alternator. This seems like it may be a bigger job? Special Tools? Special knowledge to do right?

 

[tazrig]

Re: Manifold Replacement

If... and its a big If your bolts aren't rusted in solid it really isn't a complicated job. Just time consuming. First drain the water from the block so when you remove the manifolds no water flows into the engine. Then remove the Exhaust elbows on top of the manifolds and scrape off the gasket from the elbows so the surface is nice and smooth. You'll need a gasket remover tool, something that looks like this (usually they have a razor blade on the end but you get the idea):



Then, remove the manifold bolts starting with the outside bolts first and move your way into the center. Remember the manifolds are real heavy. Remove the old manifolds and scrape the engine block gasket area completely. Put on the new gasket and manifold starting with the center bolts and moving out. Torque to factory spec. then put the elbows back on with their gaskets. Very important, don't re-use the old bolts buy all new ones and make sure they are the strengthened ones. (you can get all this on iBoats)

Good luck!

 

[Jake007]

Re: Manifold Replacement

OK, so I should try to see if the bolts break free and if so, go ahead with the job or else bring it in to get worked on by someone that knows how to get them out. How hard can I pull on the bolts before they break off? Use an 18" breaker bar? Pipe extension on the breaker bar?

 

[tazrig]

Re: Manifold Replacement

You shouldn't have to use a breaker bar. If they are in there that tight try soaking them with some JB Blaster overnight. If they still won't budge I'd just turn it over to the pros at that point to let them try heat and other top secret tricks they have picked up along the years etc. Then if they break off they get to deal with the fun of drilling and re-tapping to get them out. Nothing a pro mechanic loves more than getting a half completed job with broken off bolts that he might have been able to save.

 

[jerryjerry05]

Re: Manifold Replacement

The job ain't that hard.The mani's are heavy that's the hard part.
15 years is old enough.
The bolts should'nt be that hard to remove.I've done a bunch of mani jobs and 99.9% were easy.
You should get new bolts with the mani kits.
The reason manifolds go bad is the expansion/cooldown and air.
Salt water will rust them faster.Flushing will help.
Draining them and leaving them empty will accelerate the rusting.
Where in Fl?? Profile,location. You might be close to someone who can help??

 

[aerobat]

Re: Manifold Replacement

i replaced mine manifold last year and the bolts were no problem. assuming you have a good toolbox you should be fine.

the job is not very hard to do, the only pain in the @ss was to clean the head from the old gasket and handling a heavy part with limited space available.

 

[Jake007]

Re: Manifold Replacement

The estimate I had for this repair was ~$1500. Wow, I am starting to feel like I might be able to do this repair. So I will spray with PB Blaster the night before, then give them a pull with a standard ratchet. If they all start to come loose, order the parts and get'er done. I am in Orlando.
So the parts I should order are just the two manifolds and attaching bolts which may come with it, any other parts? Elbows? Elbow gaskets, etc?


Thanks for the advice guys!

 

[tazrig]

Re: Manifold Replacement

They typically come in all inclusive kits but if they don't you will need (per engine) 2 manifolds, 2 gaskets, new bolts, drain plugs for new manifolds, (don't re-use old ones) fittings that screw into the manifolds for the water hoses to attach to. Also if the elbows are as old as the manifolds then replace them too. Also with new gaskets and bolts. If the rubber water hoses are dry rotted or "crunchy" when you squeeze them they should also be replaced. If the large hoses that the elbows go into are cracked or badly dry rotted replace them as well. It is also not a bad idea to replace all the hose clamps to both the water hoses and the elbow hoses unless they are in perfect condition. I know this sounds like a lot of parts and expense but better to replace everything in the line now and not have to think about it again for 5-10 more years than replace only some of it and potentially have some of the rest let go the next time you take the boat out. Boating is all about preventative maintenance. I had a pair of Merc 5.7L i/o's that lasted 22 years without a single breakdown because of preventative maintenance. You can get all of the above parts on iBoats.com you just need to tell them what year make and model of engine you have and they can look up the specific parts for you. One more thing. always replace things in pairs. In other words don't just replace one elbow on the motor or one hose. If you have twin motors then whatever you replace on one motor be sure to replace on the other. At least as it relates to mechanical parts.

If you are going to do repairs on the motors yourself it's always a good idea to get a factory service and parts manuals from the manufacturer for your motor. If money is tight you can always view most them here thanks to Don S. putting together the following links. For example here are some of the Mercruiser links:


http://forums.iboats.com/mercruiser...cellaneous-mercruiser-information-329915.html

 

[bruceb58]

Re: Manifold Replacement

You should replace the risers at the same time. Personally, I prefer going with OEM manifolds and risers. They cost more but are of better quality than the aftermarket ones.

Tazrig, any reason your posting Mercruiser links when the OP has a Volvo?

 

[jerryjerry05]

Re: Manifold Replacement

What motor you working on?I'm guessing a V/8 of some sort.
Manifolds,risers and all the gaskets.
You shouldn't need sealer.
Maybe the rubber boots?They are 15 years old too.
New hose clamps.
While your at it, the belts and a new impeller?
The original equipment is a bit more pricey.
I have used Barr and Osco with no problem.
Check this site and Amazon for prices and delivery.
At that cost the delivery should be free???

 

[bruceb58]

Re: Manifold Replacement

You shouldn't need sealer.

If you are talking about the Riser/manifold gasket, you should consult the instructions with the Volvo gaskets. They seem to change over time.

 

[tazrig]

Re: Manifold Replacement

You should replace the risers at the same time. Personally, I prefer going with OEM manifolds and risers. They cost more but are of better quality than the aftermarket ones.

Tazrig, any reason your posting Mercruiser links when the OP has a Volvo?

I was just giving an example of what's available on the site. Where does the OP say he has Volvo and not Merc?

 

[bruceb58]

Re: Manifold Replacement

Where does the OP say he has Volvo and not Merc?

Well...posting in the Volvo section is probably the biggest clue.

 

[Jake007]

Re: Manifold Replacement

Wow... here we go.....
Engine is a Vovo 5.0 GI. I know you guys are right but I hate to part with the cash. I am a strong believer in preventative maintenance. I can't stand being embarrased with a group of friends while setting out for an awesome boating day only to have a breakdown. As mechanical things age, the old "while you are at it" repair clause gets more and more applicable. I will take a look at these other items before ordering anything so I avoid the 5 trips to get parts that I usually take. I have been wondering about the water hoses for the last few years myself but wherever I go most folks say they are fine. I am guessing that they are not under as much pressure as a car since the system is an open system? Mine have never been replaced and are kinda stiff/crunchy. Belts are new and water pump changed last month.

As far as draining the block comment earlier, did that mean open the drain plugs on the manifold or a different drain?