Need advice on when to change manafolds

Michael Mirra

Member
Jan 18, 2017
176
Rock Hall, Md
Boat Info
360 Sundancer 2002
Engines
8.1 Horizon X 2
This is my second summer with my new to me 2002 360 Sundancer with 8.1 horizons. When I purchased it I was unable to get any service records. I had the boat and engines surveyed with very good results. My question is how do I know what to look for or when to change my manifolds. I took the risers off the port engine for a repair and from what I could see there was no rust just black carbon. My dilemma is that I have been hearing about aluminum manifolds on these boats. I put a magnet on each and it only stuck to one on the port side. Hard to believe they are original after sixteen years, and why would someone only replace one side of one engine. The boat was bought on the Chesapeake bay but could have been in fresh water. I had it in salt water in New Jersey last summer and in the upper Chesapeake this summer
 
If the boat was fresh water it's possible they're factory. If it was me, I'd replace them both now with OEM risers and manifolds, just to set a baseline since you didn't get any service records with the boat. Especially since you're running in salt water now.

Sometimes people only do what's necessary to either sell the boat, or get a few more months out of it until summer ends. It's possible the PO only replaced the side that was leaking or showing signs of aging.

To answer your question, you're looking for rust stains around the gaskets between the manifold and riser or cracks in the manifold itself. Even though you've inspected them and found no outward signs of defect or leaking, doesn't mean they won't in the future. Better safe than sorry when dealing with risers and manifolds.
 
I agree with just replacing them now to get a baseline. My last boat had the original risers and manifolds from 1986 but it was all freshwater usage.
 
We have cast iron risers. The risers are the only part that sees salt water. I tend to replace them based on white smoke coming out of them. They generally last 3 years with no white smoke then in year 4 it starts and in year 5 there is more. The smoke is the salt water in the riser boiling off when the engines are started. At 5 years the cast iron looks good but it is soft and will chip off 50% of the mating face in areas. I was quoted 8K to replace mine. You can do it yourself for 2K.
 
On the 8.1s you will more than likely only need to replace the manifolds (and risers if you have them) the elbows are stainless steel. I would fill them and make sure they are not leaking back to the manifold. I was told it's an easy test when off.

-Kevin
 
I don't have risers. Elbows are suppose to be stainless and appear to be in perfect condition. The magnet didn't stick to the elbows, should it? Any suggestions on the best place to purchase OEM manifolds/ I'm probably going to put this off until after the boating season.
 
I don't have risers. Elbows are suppose to be stainless and appear to be in perfect condition. The magnet didn't stick to the elbows, should it? Any suggestions on the best place to purchase OEM manifolds/ I'm probably going to put this off until after the boating season.

Magnets generally do not stick well to stainless. You can see if the elbows are cool to the touch when the engine is warmed up. If they are very warm then it is indicative of a water flow problem that could point to rust blockage in the manifolds if water pressure at the raw water pumps looks good.

I am a big fan of doing manifolds in the spring before launch. I don't like them to see water in the fall and then sit over the winter with a potential to begin rusting.

-Kevin
 
If you are in salt water now, replace them. I bought a 2004 3 years ago and still had Aluminum manifolds. The boat was in fresh water it's whole life. I went 1 season in salt before I replaced them. I was surprised how good they looked. Once in salt I was told 3 years they last. Be safe then sorry.

Elbows are stainless steel. Just look at the welds. If they are OK and no cracks you are good to re-install.
 
Your stainless elbows should be fine but I would change the manifolds now, using OEM E coated replacements, and since you’re in salt water I would change them every fifth year.
 
im a firm believer in OEM but i had to budget and just replaced my manifolds, extensions and elbows with Barr Marine I found on Ebay (great seller, pm me I can find their name) i think i paid 1250 shipped. whole package came with all new hardware and flow gaskets/plates. Fit perfect.

I compared to OEM and you just cant tell a difference. except the wallet!
 
im a firm believer in OEM but i had to budget and just replaced my manifolds, extensions and elbows with Barr Marine I found on Ebay (great seller, pm me I can find their name) i think i paid 1250 shipped. whole package came with all new hardware and flow gaskets/plates. Fit perfect.

I compared to OEM and you just cant tell a difference. except the wallet!

Take a good hard look at them in two or three years. That’s the true test.
 
FWIW

I repowered in 2009 with 8.1s. I replaced manifolds in 2014. I did not replace the SS elbows in 2014. This year I had a hunting problem in both motors. I was too busy at work to mess with it, so I had the local Merc dealer look. Two of the SS elbows were leaking water into the exhaust manifolds (one on each engine) and down into the exhaust valves. 4 new manifolds, 4 new elbows, 4 heads to the machine shop, head bolts, gasket sets, labor and whatnot = $20k.

My advice is to replace the manifolds and elbows so that you have a baseline. Furthermore, stainless steel elbows can and will eventually leak.

I could have saved $10k - $12k if I had changed all this stuff last year myself.

Elbows = $800 x 4
Manifolds = $800 x 4
Gaskets minor

You can find the parts cheaper if you shop around the Internet. I would also suggest that you change the transmission coolers, the oil coolers and at least have the heat exchangers sent out to a decent radiator shop for testing. The last thing you need is sea water in your transmission or engine oil after spending that kind of coin on exhaust parts.

Your mileage may vary.

That said, we just ran the boat from Virginia to Atlantic City, NJ and back last week and didn't miss a beat.
 
FWIW

I repowered in 2009 with 8.1s. I replaced manifolds in 2014. I did not replace the SS elbows in 2014. This year I had a hunting problem in both motors. I was too busy at work to mess with it, so I had the local Merc dealer look. Two of the SS elbows were leaking water into the exhaust manifolds (one on each engine) and down into the exhaust valves. 4 new manifolds, 4 new elbows, 4 heads to the machine shop, head bolts, gasket sets, labor and whatnot = $20k.

My advice is to replace the manifolds and elbows so that you have a baseline. Furthermore, stainless steel elbows can and will eventually leak.

I could have saved $10k - $12k if I had changed all this stuff last year myself.

Elbows = $800 x 4
Manifolds = $800 x 4
Gaskets minor

You can find the parts cheaper if you shop around the Internet. I would also suggest that you change the transmission coolers, the oil coolers and at least have the heat exchangers sent out to a decent radiator shop for testing. The last thing you need is sea water in your transmission or engine oil after spending that kind of coin on exhaust parts.

Your mileage may vary.

That said, we just ran the boat from Virginia to Atlantic City, NJ and back last week and didn't miss a beat.

I used these. I flush my engines EVERY time I come back to port. Not planning on replacing them in 5 years. The aluminum ones used in fresh water for 14 years looked new.
Manifolds = $580.69 x 4. This is for the kit. It's used to convert the water rail type, but Includes everything you need. https://nuwavemarine.com/oem-mercru...manifold-866178a02-water-rail-conversion-kit/

Elbows = $563.69 x 4. I don't think these would need replacing. Since he was in fresh water it's whole life. https://nuwavemarine.com/oem-quicksilver-mercury-exhaust-elbow-865332a02/
Gaskets minor
 
FWIW

I repowered in 2009 with 8.1s. I replaced manifolds in 2014. I did not replace the SS elbows in 2014. This year I had a hunting problem in both motors. I was too busy at work to mess with it, so I had the local Merc dealer look. Two of the SS elbows were leaking water into the exhaust manifolds (one on each engine) and down into the exhaust valves. 4 new manifolds, 4 new elbows, 4 heads to the machine shop, head bolts, gasket sets, labor and whatnot = $20k.

My advice is to replace the manifolds and elbows so that you have a baseline. Furthermore, stainless steel elbows can and will eventually leak.

I could have saved $10k - $12k if I had changed all this stuff last year myself.

Elbows = $800 x 4
Manifolds = $800 x 4
Gaskets minor

You can find the parts cheaper if you shop around the Internet. I would also suggest that you change the transmission coolers, the oil coolers and at least have the heat exchangers sent out to a decent radiator shop for testing. The last thing you need is sea water in your transmission or engine oil after spending that kind of coin on exhaust parts.

Your mileage may vary.

That said, we just ran the boat from Virginia to Atlantic City, NJ and back last week and didn't miss a beat.

I'll second this concerning the stainless elbows. I was told by a local marine mechanic that even though they are stainless, they will tend to corrode / pit and begin to dribble down into the exhaust.
 
If the boat was fresh water it's possible they're factory. If it was me, I'd replace them both now with OEM risers and manifolds, just to set a baseline since you didn't get any service records with the boat. Especially since you're running in salt water now.

Sometimes people only do what's necessary to either sell the boat, or get a few more months out of it until summer ends. It's possible the PO only replaced the side that was leaking or showing signs of aging.

To answer your question, you're looking for rust stains around the gaskets between the manifold and riser or cracks in the manifold itself. Even though you've inspected them and found no outward signs of defect or leaking, doesn't mean they won't in the future. Better safe than sorry when dealing with risers and manifolds.

Solid advice.
 

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