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Stainless Manifolds and tubes


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No Money matters but Stainless Marine makes a set and I know a lot of performance boaters use them I think they are actually have an aluminum jacket. from the website.

Big Block Exhaust Manifolds Risers / Tailpipes
Our Marine Engine Parts-Big Block Exhaust Manifolds Systems feature state of the art design
with single wall internal casting that is enclosed in a press formed
aluminum jacket creating a fully water cooled manifold. A highly polished
stainless steel risers comes standard as well as bolts, gaskets and fittings

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Why would anybody use 2 different metals in a very hot SALT water system.  The corrosion risk & expansion rates are not good. Corrosion of Aluminum in hot salt water is not a good idea.

All stainless with WELDED joints is the correct way.     S S & Aluminum ??  You better not ever fire up DRY & rev it a few times.

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  • 3 weeks later...

If your going to keep your boat, say for the next 10 years+. Wellll maybe??

Myself, I have had my boat for the past 6 years. I expect to get another 2 to 3 years out of the manifolds and risers. I HOPE that in the next 1 to 2 years to sell this boat, for a 32 or 34 footer.

So to spend that kind of money, one must really think about. When am I buying my next boat?? Rather than using stock manifold.

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2 hours ago, Hatem said:

I need to find out if it's the 3" or the 6"

Hatem, with your picture, you have the 6-inch variety.  To confirm, the elbow is about 7.5 inches tall (from the top of the casting to the underside of the machined flange).  The standard version doesn't use a riser, but the elbow is the same (as used with the 6-inch).  The 3-inch uses a different elbow; single piece elbow/riser. 

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His point about dissimilar metals is good and accurate. I’d stay with the OEM. You know what the performance has been, and therefore will be. Actual life is unknown on the stainless/aluminum option. Could be better, could be worse. Won’t know until some point in the future, and before then you might catch 2 to 3-foot (or more) itis.

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As a possible alternative Chevy water cooled headers. Many older Jersey Skiff racing boats have solid polished Aluminum header. I still have many contacts in that engine class if you are interested.  A side note about the Aluminum headers.   They NEVER turn colors when run WOT for long  high temperature  periods.  S S can & does easily if overheated They also warp & cause difficult to correct exhaust manifold to cylinder head leaks.. 

Do search out marine  Aluminum Chevrolet exhaust headers. Big & small block..  Did / does G M offer Aluminum headers on the racing engines ?

Good news................  www.cpperformance.com  still is around.

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Aluminum heats up the same, just gets there and dissipates faster. It’s vastly more thermally and electrically conductive. Cast iron, though, holds heat longer (a heat sink). Aluminum is a reactive metal. It corrodes, more so in salt water, and especially when dissimilar metals are involved (whether yours or what’s nearby). The corrosion takes the form of a white skin (which, when significant, complete and quickly developed, is actually a barrier to further corrosion) often with a bit of a powdery appearance and feel. You’ll need to watch the anodes, and may need to change the type. In addition, given you’re splashed at a marina, in salt, neighboring slips, boats, types of metals, shorepower and electrical leakage all become more relevant and part of the success (or failure) equation. Aluminum is more reactive than iron, steel, bronze, etc. It’s all been considered by the manufacturer, thus the 5 year warranty vs. lifetime (where common knowledge and thought would suggest aluminum and stainless should be lifetime). Your call.

P.S. What’s depicted by the picture looks normal. Assuming no leaks, if they flush clean and there’s no solid debris, replacement is premature and another season to three is expected. Also, current generation VP’s are all aluminum, including exhaust manifolds, risers, etc. Lighter but also eliminates the dissimilar metals problem.

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I know its a expensive upgrade over  the Volvo brand if I go with Stainless, I am average about 5-6 years on the cast iron so other then the slight performance  gain, I don't think the stainless will be worth the extra price.  Also like all 256 I have 11" riser on mine to avoid water back up the tubes.  

I already over spent my budget this year when I had to pull the motor to replace the starter and of coarse all the extras while it was out.

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Recall, none of us have knowledge of quantity leaking or visual of your bilge. Only you do. Based on the posted pictures, and considering age, it’s great and I don’t get all hubbub regarding stainless. (Also, not poking you here, but a header and manifold are different. A header is generally used with a different objective in mind.). Yes, if at that age and that minor, I’d go another season and reassess. I’d also replace with cast Volvo Penta. FWIW, the small leakage looks more like uneven torque, or a little heat induced warpage. Don’t attempt to retorque now. It will get worse. Congrats on Red Sox.

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I agree with you completely Hatem.  Time to pull all the exhaust castings apart & see what is still salvageable.  I certainly would. The leaks can go back into the engine on shut down . Or spray outward all over the engine & ruin connectors.   We are talking hot enough water & pressure to ruin wires, connectors  or bilge pumps. Belts.    Heck you have been lucky enough to know what could be coming hours from a return in bad weather...…….. Do it. We will both sleep better.  Good luck on the repairs.  Post back for others to check their boats.   Save some others from a ugly break down.

The best to you.

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In my 14 years old childhood ??  :haha-7383:    I worked in a AUTO RADIATOR repair shop. WE did rads, heads, marine water everything.  Gaskets can get squished very thin & look like those pictures.

We would clean holes in the moving flow acid tank. Deep rusts went to a machinist & welding place for a perfect  resurfacing job.  Back then NEW was a unused word. Pull the parts apart Clean the rust off & have a crack check done IF the parts look that good. ANY GREAT auto machine shop will do ALL your needs . Marina is going to send your stuff there anyway...Save a couple of thousand.

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On 11/6/2018 at 5:18 AM, Hatem said:

I'm curious if anyone has ever just changed the gaskets only?

Yes. A handful of suggestions follow. Check mating surfaces. They need to be clean of debris, corrosion, etc. This is usually accomplished with a wire brush and emery cloth. If real bad but internal passages are good, they can be re-decked (surface milled; just a skim cut if you will) (about any auto machine shop can do it; small $). Use new bolts and a two or three stage torque regimen in the prescribed alternating pattern. Apply a brush width patch of anti-seize about an quarter inch above max. insertion depth. This keeps water from penetrating deep and freezing the bolt in place. Chase all threads with a tap, then clean all debris out with compressed air or shop vac and snout.

A reminder... I don't know how much leakage you have and only have the static photo to go from. Setting that, the stainless debate and whether I'd reuse as-is aside, Cyclops and you are both on point with disassembly and inspection. It's easy, and if you don't like what you see, you can then move to replacement. No real wasted time or effort, and your mind will be at ease whether used another season or replaced. Best wishes.

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  • 1 year later...
On 10/26/2018 at 2:22 PM, Hatem said:

Currently at the VP distributer getting all my goodies for winterizing and the manager is such an awesome dude really helps me out all the time I'm in here, spends a ton of time looking for the right parts and numbers etc. and I was looking to get the stock risers and manifolds quoted and the original parts numbers  from 2010 were discontinued, but for the replacements I need to find out if it's the 3" or the 6".  Either way, worst case scenario for the pair of risers, manifolds AND Y-pipe came out to $2,360.  Anyone with experience in these 8.1 VPs know if that's basically the average price for all that?

That way we can compare if the difference in upgrading to stainless steel would be worth it.

I changed the risers and manifolds on my Merc 8.1 and the total cost for all parts was about $1900. I did not need a Y-pipe, so perhaps my costs are similar to yours. 

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