What happens when manifolds/risers fail?

Johnshan1 · Feb 12, 2009

I have a 2000 Larson 254 Cabrio with a 5.7L GL Volvo Penta engine in it. I have never replaced the risers or manifolds and know I am on borrowed time. I need to do some other things to the boat this year, and replacement of risers and manifolds is schedualed for the late fall of '09.

If a riser of manifold were to fail I understand water can enter the engine, but would it lock up if running?

Thanks for any info on this.

Johnshan1 · Feb 12, 2009

Re: What happens when manifolds/risers fail?

Also, it is RWC in salt water.

I have 440 hours on the boat, expect to hit 600 this season if all goes well.

Thanks again for any input.

Bondo · Feb 12, 2009

Re: What happens when manifolds/risers fail?

If a riser of manifold were to fail I understand water can enter the engine, but would it lock up if running?

Ayuh,..

Anything is Possible,....
And,..
You've gotta shut it Off at some point....

HT32BSX115 · Feb 12, 2009

Re: What happens when manifolds/risers fail?

Howdy,

Sounds like you want to get one more season in before replacing everything.

If they start leaking while you're out there you might not notice it at all....except when you shut it down.

Mine had leaking riser gaskets. Every time I shut down to pick up a skier etc, a small amount of water would run into an open exhaust valve. Then a few min later when I tried to start it it would "hydrolock" briefly.

If I let it sit over night (or more than about 2 hours or so) it would crank normally. Presumably the little bit of water that did run into the cyls leaked past the rings after a couple of hours........or over night.

After you park your boat and the salt water runs into the inevitably open exhaust valves and sits there for the several days or couple of weeks, when you get back to the boat, that's when you'll notice the problems. It doesn't take long for salt water to destroy a bare steel cylinder

This is just if the riser gaskets are leaking or you have internal cracks/corrosion paths that allow leaks.

My suggestion: Pull your risers and inspect. If everything looks acceptable you only replace your gaskets and bolt it back together...... It would be a really good idea to know.....

If there's even a question you can just replace it all now.....but you would operating from a position of knowing instead of wondering.......

Cheers,

Rick

iang · Feb 12, 2009

Re: What happens when manifolds/risers fail?

Here in Australia Volvo insist on annual inspection of riser gaskets when used in saltwater,on new motors you will void your warranty if there is no proof of this being done.This should answer your question.

Johnshan1 · Feb 12, 2009

Re: What happens when manifolds/risers fail?

Thanks everyone. From the sounds of it, the failing of the manifold or riser is not so much the issue, rather the joint between them?

So, pull apart, inspect, replace gaskets? If thats all the concern really is, those mating surfaces, I will pull it apart tonight!

Thanks.

mthieme · Feb 12, 2009

Re: What happens when manifolds/risers fail?

After you pull them apart, look in the ports. They rust up. You'll want to clean out as much as you can.
This goes for the manifolds as well as the risers.

Johnshan1 · Feb 12, 2009

Re: What happens when manifolds/risers fail?

So basically- pull risers off, clean any gunk out of them, inspect to make sure its not rusted to the point of being non-structurally sound, and replace the riser gaskets/inspect mating surfaces- done?

180shabah · Feb 12, 2009

Re: What happens when manifolds/risers fail?

Deterioration at the joint = replacement. Even if it hasn't perforated yet. Some of the passages that you can't see have pretty thin walls and a failure here is just as bad as one at the joint.

winbasic · Feb 12, 2009

Re: What happens when manifolds/risers fail?

Is there much involved in removing the risers or is it relatively straight forward?

bpmcl00 · Feb 12, 2009

Re: What happens when manifolds/risers fail?

4 bolts and a couple hose clamps. the pain in the *** is getting the exhaust tube out from the back. mine was caked on and a pain in the arse to get to.

remember to replace all gaskets when putting risers back on.

i yanked mine off and took some pics heres the thread, i didnt end up replacing mine cause the passages seemed nice and thick and no major rust build up

http://forums.iboats.com/showthread.php?t=287513&highlight=manifolds+risers

rodbolt · Feb 12, 2009

Re: What happens when manifolds/risers fail?

for US market 5.7L VP motors its simply a matter of unbolting it and cleaning all the gasket surfaces. make sure you clean all the paint from the gasket surfaces of the new units before installing.
your on BORROWED time and do it now not next fall.
engine box access is a whole nother question.

Johnshan1 · Feb 12, 2009

Re: What happens when manifolds/risers fail?

Thanks guys. How long do manifolds last? Engine access is awesome on my boat, I can go down into the bilge and sit right beside the engine, tons of room in my "engine room".

Do manifolds typically fail or not? Is it just the gasket mating surface that is the issue?

Bondo · Feb 12, 2009

Re: What happens when manifolds/risers fail?

Do manifolds typically fail or not?

Ayuh,.... Sure Do,....Especially on raw water cooled Saltwater boats....

bpmcl00 · Feb 12, 2009

Re: What happens when manifolds/risers fail?

if you could guess. what are typical ammounts of hours or years that you can get on a freshwater cooled manifold??

iv heard anywhere from 4-40 years for FRESH WATER only

rdj59 · Feb 12, 2009

Re: What happens when manifolds/risers fail?

Took 35 years for my risers to rot out.

superpop · Feb 12, 2009

Re: What happens when manifolds/risers fail?

I replaced them on my old boat after 11 years just because I was paranoid. Took the old ones off when I had the motor out to replace all the gaskets and seals and did the manifolds and risers at the same time. Really easy to do and it is a lot of peace of mind. Mine probably were fine but I figured I might as well replace them while the motor was out. Under 500 bucks in parts from Michigan Motors and they worked like a charm.

Lupus · Feb 13, 2009

Re: What happens when manifolds/risers fail?

Hi guys,

I know we are talking freshwater here (4-40 years) and I guess this is right. I have my boat in saltwater (raw water cooled too...) and I replaced the manifolds and riser after just 5 years of operation (450 operation hours). I did not do this because of fun BUT because they were worn out. Guess this truely prooves the different between running in freshwater or saltwater.

Bondo · Feb 13, 2009

Re: What happens when manifolds/risers fail?

(4-40 years)

Ayuh,...

That translates from Saltwater(4 years) to Freshwater(40 years)......

Johnshan1 · Feb 13, 2009

Re: What happens when manifolds/risers fail?

I have done the search on GLM manifolds and risers, it is about 50/50 on the thoughts of quality. Has anything been done as of recent to improve their quality or has anyone bought these recently?

I read your post Bondo on the surface not being flat.

Are these ok or not? Sounds like some are, some are not. Buy them and check the mating surfaces?

What happens when manifolds/risers fail?

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