Risers

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jhr

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Eight killer words at the bottom of the engine report from the yard after they took the boat out for the winter last week: "Rust around exhaust risers, recommend removal and inspection".

In truth, I can't complain; the risers are the original ones (2001) and have lasted better than I have a right to expect. I had already noticed tell-tale streaks of rust seeping out and was resigned to the fact that they would need replacing soon.

However, before I re-mortgage the house, any views on the labour time needed to do the job, and the cost of the bits (assuming OEM)? Also, I'm sure I have read somewhere that you can buy stainless risers, though no doubt at a price. Anybody got any experience of these and whether the extra cost would be repaid by increased longevity? Engine is a Mercruiser 5.0l efi, conventional installation on a 21 foot mobo.

PS Anybody considering suggesting that I DIY it has obviously never witnessed the carnage that I bring to even the simplest mechanical task :)

TIA
 
Uh-oh, Break Out Another Thousand.
Manifolds and risers on petrols in salt water are a bit disposable. They did well to last eight seasons.
 
jhr said:
I'm sure I have read somewhere that you can buy stainless risers, though no doubt at a price. Anybody got any experience of these and whether the extra cost would be repaid by increased longevity? Engine is a Mercruiser 5.0l efi, conventional installation on a 21 foot mobo.
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Short answer, NO.
S/S headers cost almost 5 grands, and they don't add anything to engine performance (in spite of producers claims), unless you're further tweaking the engines e.g. with blowers.
Besides, they're mostly built for big blocks: I've never seen them on 302 and 350 engines.
That said, boys, do they look gorgeous in the engine compartment!

PS: the better way to protect your new headers (and not only them) is to ask your mechanic to fit also a 10 quids 3 way valve to the cooling circuit, allowing a fast and easy connection of a hose, to flush the whole cooling circuit with fresh water after using the boat. Worth doing also with S/S headers, btw.
 
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Hi,

I've just changed the manifolds, spacers and elbows on Mag 350. It cost me about £700 in parts from Trickett Marine, took me half a day and was very easy. Get yourself an engine manual and follow to the letter and you'll not go wrong. I'm not a technical man....although I've become more hands on since owning the boat, use care and a bit of common sense and you'll be fine!!!

Good luck

Paul.
 
Its not the end of the world, labour charges not a lot, if its the manifold risers its a simple unbolt job, both manifold off, make a good inspection, maybe if there not too bad they can be cleaned up and painted, but if there rotten then its new ones and a few gaskets.

While they are off examine to cow horns or exhaust pipe to the transom shield, presuming you dont have transom exhausts.

If the pipes are rotten at the top volvo do a plastic conversion type liner that seals the hoses on the volvo models.

If the pipes are beyond repair it may be engine out to get at the bolts at the bottom of the transom shield.
 
jhr said:
In truth, I can't complain; the risers are the original ones (2001) and have lasted better than I have a right to expect...

However, before I re-mortgage the house, any views on the labour time needed to do the job, and the cost of the bits (assuming OEM)? Also, I'm sure I have read somewhere that you can buy stainless risers, though no doubt at a price. Anybody got any experience of these and whether the extra cost would be repaid by increased longevity? Engine is a Mercruiser 5.0l efi, conventional installation on a 21 foot mobo.

PS Anybody considering suggesting that I DIY it has obviously never witnessed the carnage that I bring to even the simplest mechanical task :)

TIA
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On the Bayliner Owners Club forum they reckon you should be looking at 5 years max. from your manifolds and risers in salt water, 10 years in fresh so, as you say, you can't complain.

I've just changed mine. Well, I'm lying really. A forumite of this parish had recently changed his and he kindly offered to give me a hand. I'm embarrased to admit that this resulted in me standing around looking gormless (which, BTW, I'm very good at) and handing him the required tools whilst he did the job! I might add that he did the job excellently in a couple of hours - plus beer breaks, so, er...about four hours or so. :rolleyes:

I might add that, like you, I fear I would still be on my boat now completing the job without this guy's help. I'm reasonably competent with the spanners, but if I'm unsure of what I'm doing I work so slowly for fear of cocking up.

I'm happy to state that I felt sufficiently grateful to said forumite that I have offered to have his babies. :eek: Fortunately, he declined my offer. :o (phew...)

As Mario said, don't bother with stainless risers. As well as the cost issues, word is it's difficult to ensure a gas/water tight seal due to the varying expansion rates of SS and cast.

Tricketts is the place for the bits...

http://www.trickettmarineproducts.co.uk/mercruiser-manifolds.html

...cost was a reasonable (I thought) £570 (delivered) for two manifolds, two risers and gaskets.
 
I think there is some confusion here about stainless risers, Mapism is thinking about the 4 into 1 type manifolds, but Mercruiser do make a stainless riser or elbow for their engines I know as I have just found out I have them on my Magnum 350, part No 816900A.
I must be incedibly lucky, I bought a classic Draco 24 that was traded in for a song and found the boat was in unbelievably good condition throughout, easily worth £10k more than I paid for it.
However I had the dreaded water leak through the steering pin in the shield, so I pulled the engine to do my modification ( boat number 16), I thought I'd go over the 1997 motor while it was in the shop, it has freshwater cooling from new so when I took off the riser I could see the manifolds were like new inside, but expected the riser to be rusted as this is where the seawater goes out , imagine my suprise to find they were shiny inside the water passages, thats when I checked the part number and found out they were SS. And there have been no issues with varying expansion rates (re Carlton).
 
spannerman said:
Mapism is thinking about the 4 into 1 type manifolds
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Precisely. Actually I didn't know of the s/s risers you're talking about.
You've been double lucky, anyway: also the closed cooling is not standard on small blocks, afaik.
 
jhr said:
Huh! Have you seen the cost of "white flappy things"? .... And I understand that they need replacing every five years or so as well :D
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might I suggest a pair of these?

canpadbanner.jpg


I have a pair in case everything goes quiet all of a sudden, when on my perambulations upriver.
 
From what I have seen of the locally produced (Aust.), after market (not Mercruiser) SS exhaust systems, manufactured for standard small block engines, 5.0 to 5.7, they haven't been that successful.
The word is they are noisey and tend to fracture.
There has been success with a cast aluminium system (locally produced), which have a similar appearance to the genuine manifolds.

With standard manifolds and risors, the problem is nearly always at the join between the two. Its a simple job to remove the risor for annual inspection, scrape clean the two surfaces, a new gasket with a good sealant, and re-tighten in six months.
 
jhr said:
Huh! Have you seen the cost of "white flappy things"? .... And I understand that they need replacing every five years or so as well :D
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Yer jhr, don't listen to these wind up merchants.
I see the tin booter as stuck is oar in too:)

V Paul and others have given good advice as usual:)

A Man of your Calibrer can do it!

Or get a sensible boat with a shaft drive innit:p
 
spannerman said:
but Mercruiser do make a stainless riser or elbow for their engines I know as I have just found out I have them on my Magnum 350, part No 816900A.
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That's an obsolete item, and no longer available. Had to many failures due to the different expansion rates of cast iron and stainless, causing the gasket to fail.
 
I had a leaking manifold to riser join, with a rusty stain on the manifold; I was expecting the worst when I took it apart last winter.( a 2004 Volvo Penta 5.7GXi, 4 years use in salt water). I was pleasantly surprised, it was only the gasket. There was remarkably little corrosion, I put this down to having VP's "Neutrasalt" system fitted and used ever since the boat has been used in salt water (with closed cooling fitted to protect the engine and inlet manifold at the same time).

I also removed the manifolds to give them a clean up and repaint. Again, virtually no corrosion to be seen.

The worst part of the job was scraping off the old manifold gaskets!

The manifolds are heavy; it's easier to replace them if you cut the heads off some bolts and screw them into the head first; the gasket and manifold can then just be slid along the bolts, no chance os a mis-aligned gasket etc. I used a couple of riser bolts ( I needed 2 new ones as the old ones were bent slightly; no idea why!).

Incidentally, VP recommend that no additional sealer is used on the gaskets.

Graham
 
GrahamHR said:
Incidentally, VP recommend that no additional sealer is used on the gaskets.

Graham
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Graham...........They (VP or Merc.) may not recommend sealant be used, but with all the failures at that point.....I think it needs all the help it can get. ;)
Going around the bolts with a socket, periodically, is a practice that is advise-able.
 
Changed mine earlier in the yaer, was not a particuarly complicated job , just heavy getting the manifolds in place. I used Trickett marine for the new manifolds and can not recommend them highly enough.
 
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