New Exhaust Manifolds

[martinarcher]

Hey all,

My port side manifold is starting to leak and has been fixed in the past with JB weld or something similar. It is still leaking rusty water and I figured I would just drain the manifold, "V" out the leak spot and re-fill with JB weld. Well I drained the manifolds a couple times while winterizing and the port side mani is really rusty. Big flakes coming out with the water. That tells me that the exhaust/water passage walls are probably beginning to deteriorate. They are 23 years old so no shame there.

I decided I should just replace both sides and the risers while I'm at it. It won't be cheap, but, well she deserves it.

So onto my question for those who might have done this.

1. I found after market manifolds that look just like mine that are cast out of aluminum. The plus would be longer life and lighter weight. Life isn't too big of a concern since the old ones lasted 23 years and are iron. Here's one I'm looking at.

2. Just replace with cast iron from Sierra or similar. Here's one.

3. Stop being a sissy and go stainless and let some ponies out of my motor. I haven't looked into this one yet, but know they are pricey. I also know they are lighter weight and would be much higher performance.

What do you guys think? Any other ideas? I'm leaning toward the aluminum direct replacement, but I wanted other opinions. I know woodski replaced his with after market for power gains and weight savings so I thought I would see what everyone thinks.

Thanks!

[Ozfabs]

I run in salt water 95% of the time & pulled off my manifolds a few months ago for inspection - Not great!! Guessing I'm only going to get 3 years tops out of them.

I looked into these http://www.hitekmarine.com.au/ here on the Gold Coast and they will be my best option when the stock ones fail.

A few more horses would be nice!!

[martinarcher]

I run in salt water 95% of the time & pulled off my manifolds a few months ago for inspection - Not great!! Guessing I'm only going to get 3 years tops out of them.

I looked into these http://www.hitekmarine.com.au/ here on the Gold Coast and they will be my best option when the stock ones fail.

A few more horses would be nice!!

I've actually got an email to them waiting for a price quote. Hopefully they aren't as expensive as they look, but I'm not holding my breathe! They do look sweet!

[Woodski]

Martin: 700+ hours accumulated on my Stainless Marine aluminum units and still going strong. Significant weight savings from the aluminum is a positive particularly for a slalom skier. The power improvement comes from two areas, actual runners in the primary side which evens out the pressure pulses and a much larger cross sectional area at the primary / secondary joint and elbow. If you get the stainless elbow, you add to the bling factor! One thing you will notice on the aluminum manifolds, they tend to use up gaskets pretty quick, about 2-3 years due to expansion and contraction differences from the heat. The aluminum units will also stay much cooler than cast which is a nice thing under the engine hatch. You are right, they are not cheap and if you have a stock Mercruiser I am not sure what the power gain would end up being. I did mine due to a lot more airflow and the weight reduction.

PS: those Hitek units look pretty cool and probably perform great. I think Bassett makes a similar one in the US. I would get dimensions as they look pretty tall from the picture and also see if the outlet can be set at the angle you want. When you do these type of mods, squeezing that 4" tube down through the floor gets a little tight but can be done.

Edited November 1, 2010 by Woodski

[martinarcher]

Thanks for the reply. I talked to the guys at HiTek today and the Aussies said they would be about $2200 for a pair for my Merc. He said I would get 30 hp and 45 ft lbs of torque by swapping to their mani's. That's a bit rich for my blood just for manifolds. I like the 45 ft lbs of torque, but there are cheaper ways to get power. I'm leaning toward the aluminum route now. Bummer about the gaskets, but they are pretty cheap and at least the manifolds are way lighter which makes gasket replacement easier!

I looked quick for the Bassett manifold and just found a trumpet header like what you would see on a go fast boat with a chromed V8. I'll keep looking.

[Levi900RR]

Get some headers and put them on upside down!

[martinarcher]

Get some headers and put them on upside down!

I was looking at some dry exhaust/header options, but I'm worried about the heat melting or damaging my dogbox.

I found a site with a ton of options though....

http://www.boatstoreonline.com/

[eyepeeler]

My RLX is 10 years old and has the Monsoon with the cast risers. I have never touched the gaskets and there are no drips or trails from the gaskets. What is everyone doing? Do you wait until there is a problem or go in and check the gaskets and water jackets?

[martinarcher]

Typically it seems to be pretty normal to get 20 years out of cast manifolds if they are used strictly in fresh water.

I always watch the water I drain from the manifold in the fall when the night time temps are getting cold. If the water looks rusty or has rust scale in it I think it tells a story about the interior health of the manifold itself.

If you read online about manifold health they tell you to pull them (or at least the risers) every fall and inspect them. I can see doing that if you run in salt water a lot, but not for strictly fresh water use. They also say to change them every 5 year, but they are the ones selling them.

[martinarcher]

Well here's what I've come up with after a few evenings of reading and researching what's out there for the Merc small block.

CHOICE # 1 GLM aluminum performance manifolds and risers....

1. Separate cambers for each cylinder that collect just before dumping into the riser. The riser does not keep each cylinder's exhaust gases separated.

2. Claim 10% performance increase. Found a few forum posts with guys claiming dyno tests between these and the high dollar stainless manifolds to be the same on hp numbers and 2 ft lbs less on torque. Sounds like I would be looking at about a 22-26 hp gain.

3. Also found a couple posts claiming to find water in cylinders a year or two after installation. They claim the when the manifolds are new, the mating surfaces are not machined perfectly flat causing the gaskets to fail early and leak between the riser and manifold. I think if I went this route I'd swing by the machine shop and have the check them and deck them if needed.

4. These are sand cast manifolds - made in China and sold at many US retailers.

5. 3 year warranty and up to 5 year through retailer.

6. Total weight is 50lbs. Over a 90lb weight savings.

7. Total cost with hardware and gaskets right around $800. Hard to pass up.

CHOICE #2 Perf Pro Tech Aluminum Manifolds

1. From what I understand these guys were somehow associated with Merc's R&D program and worked with Mercury on exhaust back in the day.

2. I can't find any data on these, but my guess would be they are a stock Merc copy cast in aluminum instead of iron.

3. Weight would be very similar to the GLM set ~50lbs

4. 5 year warranty if you buy anodes every year. ($14 per year for 5 years)

5. Total cost with their hardware and aluminum risers would be around $1050.

6. Looks like based on the pic they are also cast in China.

CHOICE #3 GLM Aluminum Manifolds with Stainless Risers

1. Same advantages as choice #1 with a possibility of 1 or 2 extra ponies with free flowing stainless riser.

2. Probably a bit more torque as well.

3. Bling factor is cool.

4. Wallet factor is not. $1480.99 a pair.

5. As cool as this set-up looks and I think would perform, I think I'd be further off to go with choice #1 and buy stainless slash cut tips. I dunno, not sure how a stainless tube riser versus aluminum cast riser stacks up. I might call the vendor as they sell both and see what they have to say.

CHOICE #4 HiTek Marine's One Piece Stainless Performance Manifolds.

1. Made in Australia

2. Once piece of stainless bling that would arguably outlast the other 3 choices.

3. True high performance log style marine header that is still a "wet" exhaust system.

4. Dyno claimed 26 hp and 40 ft/lbs of torque increase. Most power increase of all.

5. Highest price of all - $2200 shipped to me with gaskets from Australia.

6. Can't remember what Andy claimed for weight, but I think they are right around the same as the aluminum counterparts.

Choice #5 Stainless Marine Aluminum manifolds with stainless risers.

1. Probably the best power/weight combination of all. There are some pretty big claims out there about these manifolds. Could be some hype, but I think Stainless Marine stuff is made well and does perform based on user reviews I have read.

2. Bling for the riser. Same look as choice #2, but not made in China.

3. High price. Manifolds and Risers and no hardware or gaskets will run me $1527.

4. Not too keen on how the riser/manifold mate together. It just does not seem near as fool proof and robust as the four bolt/gasket design.

Any other ideas? I'm leaning toward choice #1 because it gives me almost the same gains as the heavy hitters like Stainless Marine and HiTek at half the cost. Anyone heard much about them or used them? The only reason I can think not to go that route is they are made in China and the quality control might not be what the other vendors can provide. The biggest complaint I could find about their quality was the machined surfaces weren't perfect, but like I said above, the machine shop could fix that for me quickly, easily, and very cheap (if it's even an issue on the set I would buy).

What's your vote?

Edited November 7, 2010 by martinarcher

[ILLSMOQ]

#1 lost me on made in china (poor fit) and sand cast (stripping bolts)

#2 eeh. probably a nice lighter stock replacement

#3 looks cool but not very beefy on the riser...thin stainless like to crack after a while.

#4 those Hytek manifolds look sweet...anyone out there with real world experiance? Tough to tell how they are built from the pics...stainless cracks.

#5 looks like some pretty beefy stainless and I'd take a quality v-band clamp setup over bolts and gaskets any day!

[termite]

Gleenwood Marine Equipment make some nice stuff. They have a new cast aluminum exhaust that looks well made. A must see catalog.

[martinarcher]

Well I pulled the trigger on a pair of these bad boys today. I think Stainless Marine was the way to fly. US made and I have yet to read a bad review on them. Power gains should be pretty nice too! Is spring here yet?!?

[eyepeeler]

Martin since these manifolds are so nice and your birthday is coming up, all of the crew have decided to chip in and contribute to your new manifold fund.

[martinarcher]

Martin since these manifolds are so nice and your birthday is coming up, all of the crew have decided to chip in and contribute to your new manifold fund.

Whoo hoo! Thanks guys!

[99response]

Ouch, $1500, where was the option for 1 new cast manifold and riser

[ILLSMOQ]

Ouch, $1500, where was the option for 1 new cast manifold and riser

???? ok so this is a boat. there is no practicality when you own a boat! one does not simply replace when it comes to boats...it's alway upgrade...that is unless we're talking about a raw water pump impeller.

[ILLSMOQ]

Well I pulled the trigger on a pair of these bad boys today. I think Stainless Marine was the way to fly. US made and I have yet to read a bad review on them. Power gains should be pretty nice too! Is spring here yet?!?

sweet, looks like good stuff.

got torque specs on the manifold bolts?

fiber on steel gaskets or something else? what does indmar use?

[Woodski]

The joint between the manifold and riser on the Stainless Marine units is not an issue since there is not water actually flowing through the joint. It is a simple fiber gasket between the parts that are held by a band clamp. A good small block header gasket works fine for the head / manifold joint.

Don't forget, you probably have to purchase some 4" diameter hose to go to the mufflers. You might want to do some cross section area calculations to see where the smallest diameter section now becomes, I ended up going with 4" diameter exhaust all the way back.

[Levi900RR]

Martin, those things are going to be sweet!

[footnlongline]

I have manifold envy

[Levi900RR]

I have manifold envy

[martinarcher]

Thanks guys.

I ordered all new gaskets from Stainless Marine. The gasket between the head and the manifold is made by Mr. Gasket and goes on dry. Woodski is right, the riser/manifold gasket is simply a fiber ring gasket. Jerry from Stainless Marine told me to use a high temp silicone on both sides of the basket between the riser and the manifold.

The manifold will be here tomorrow, but I doubt the gaskets will arrive that soon from FL. I was debating if I should put them on before the boat goes into storage for the winter. I think it will make a good spring project. I'd kind of like to get some 0-30 and 0-40 time on the water with the stock cast manifolds and then put these on and compare, but I'm not sure I can wait.

Not sure on torque specs. I'll have to talk to Jerry again and see what they recommend. He's a really helpful guy. I can tell buying a US made product from them was the right way to go. Hard to beat a company that stands behind their product and will gladly help you out.

[martinarcher]

The joint between the manifold and riser on the Stainless Marine units is not an issue since there is not water actually flowing through the joint. It is a simple fiber gasket between the parts that are held by a band clamp. A good small block header gasket works fine for the head / manifold joint.

Don't forget, you probably have to purchase some 4" diameter hose to go to the mufflers. You might want to do some cross section area calculations to see where the smallest diameter section now becomes, I ended up going with 4" diameter exhaust all the way back.

My boat already has 4" rubber exhaust hose going from the riser to the under floor mufflers. Did your have something smaller?

[Woodski]

My boat already has 4" rubber exhaust hose going from the riser to the under floor mufflers. Did your have something smaller?

Yes, original was 3.0" on the Mercruiser in my boat. You will want to make sure no diameter drops below 3.5" in the entire system in order to take full advantage of the manifolds, and I made sure I was at 4" diameter all the way to the tail since water is injected at the end of the riser which takes away some of the effective area. I also set up an H pipe to add some torque.