Risers and elbows

[Maynard Rupp]

I am starting to get concerned about the corrosion in our risers and elbows. I am a fresh water guy and corroding risers and elbows is never a concern. In October of 2006 we re-located our 36C to Miami. I know that those parts can corrode through to the inside. I also know what that will do. What I don't know is how long it takes in salt water to corrode through. I have heard numbers from two to six years. I can't imagine anyone owning a boat that needs those heavy and expensive things changed every 2 years. The real problem is that the 12" "dogbones" that we have are no longer available. They do make 8" ones but I don't think they are high enough. Our current "dogbones" outlets are about 17" above the waterline. Our engines are Crusader 454cu.in. 350 hp. I need help from our salty dog members!

 

[MikeP]

Our previous boat, on Long Island, had Crusaders and I replaced the risers/elbows when we bought it, "just to be sure." They were partially obstructed but not horribly so I do not know how long the previous risers/elbows had been on the boat. I had decided, based on general reading, mostly Pascoe, that I would replace them every 5 years. But I didn't keep the boat long enough to do it again.

I bought them from these guys...http://bpi.ebasicpower.com/osco/

 

[MikeP]

Well, looking at the site, I see they do not offer the longer items you need...

I would think that as long as the bottom of the exhaust curve is clearly above the water line, it would not be an issue but I'm certainly no expert on this.
I'm pretty sure that on our former boat - Mainship 36 DC, the risers weren't that much above the water line but I can't be positive. It used the 8" versions.

 

[Beckytek]

I bought my boat in 2004 and replaced my risers in 2008. As far as I know the boat was located in long island NY for the early years and the Hudson river by the George Washington bridge for the 5 years previous to my buying it. I have no idea how old the risers were when I changed them. The shop people think they were original and they were completely shot. I am in salt water now so I think the risers will last at least 5 years and probably longer. My manifolds were perfect with no signs of erosion or ware.
I had the same problem with finding replacement dogbones, but the shop said they could use an 8 inch and 4 inch together to solve the problem. That would have worked if there was enough room in the engine room. All was well except for one leg that wouldn't pass the steps into the stateroom. Because of that I had to replace all the manifolds and risers using the new style center lift type and of course all new hoses etc. That turned into a $6600 job. The new hosing is in the way off many things and it is more difficult to work on the engine, but it's very easy to change the new risers. There is always a solution to the problem, it only costs money to solve it. Ron

 

[REBrueckner]

Maynard....
an old trick to determine level and subsequently the position of your risers with respect to your exhausts: determine level with garden hose.....
with your boat in the water with normal fuel and water load: get a length of garden hose and stick in/tape a short length of clear vinyl each end..maybe 12" or 18"...snake it through from engine riser location aft to an exhaust keep hose lower than the ends; have a person hold each end while filling with plain old water.....when the water is visible in each end...hold steady and measure the distance up or down to an exhaust reference out the stern and a reference location on the riser...those water levels at each end are precisely level and you can then tell how far above your exhaust out the stern your current risers are....and make a judgement call about shortening the risers is required....that will also depend in part on the routing of your exhaust and the type and level of your mufflers...usually mufflers will keep stern seas suppressed from rushing in but obviously there are limits...

 

[SeaEric]

On the brackish water Chesapeake, we generally advise changing manifolds and risers every 10 years. The Mercs with the center risers, maybe sooner as that center riser dumps water right down in the center of the engine when they fail. The Crusaders have the riser on the aft end, so generally the last cylinder is in peril of the raw water intrusion on failure. Many installs have the manifold on the freshwater side and only the riser is raw water. The problem is that the riser/manifold connection point becomes corroded and the new riser won't seat well to the old manifold, suggesting replacement of both components.

A few years ago we ran into the Crusader higher riser issue. We worked it out somehow, but I do not recall the outcome. There may be extensions to make them the correct height? Someone will likely post here with that wisdom.

I replaced all manifolds and risers on my 340 Mercs last season. I second the rec of www.ebasicpower.com I used the "GLM" after market set up. I was impressed that they came already painted, and in a "kit" with all parts, bolts, gaskets, etc. Everything we needed to complete the job was in the box.

Good luck.

 

[fissioneng]

I had Crusader 350's on my old boat and had to change the risers/elbows at 10 years. We are in the lower Chesapeake (more salty than upper). The tell tale sign that something was up was a slow temperature climb at higher rpm. Since the elbows were rusting and expanding on the inside, they don't pass enough water to keep the engine cool at higher flow rates. Our manifolds are on the FW side.

I have bought lots of things from ebasicpower. Everything is usually in stock and they have a great shipping policy.

Be careful with the riser height above the waterline change. We had a repowered boat in our marina go through several engines due to improper riser height and salt water was ingested back up the exhaust ruining several engines.

 

[mobilemn1]

Maynard,

don't know if this will help but they have a good selection of crusader parts. And don't know if these are like yours or not, but they match the ones on my boat, installed in 1999 http://www.marineparts.com/osco/osco20.aspx

 

[Genesis]

Crusader has a MUCH better design than Merc on these parts BUT in salt water my "rule of thumb" is ~5 years.

You may get more (and might get less) but the price of a failure is a trashed engine.

 

[fissioneng]

Crusader has a MUCH better design than Merc on these parts BUT in salt water my "rule of thumb" is ~5 years.

You may get more (and might get less) but the price of a failure is a trashed engine.

If I was still worrying about this, I agree. 10 years was really pushing it. The parts aren't THAT expensive and they tend to be VERY difficult to disassemble. The risers tend to weld themselves onto the manifold and its studs. A shorter change out should make them easier to remove.

These things are like raw water impellers, better to change more often than you need to.

 

[Passages]

I would agree to 5 years in Florida saltwater where you have a 12 month boating season.

Cold weather folks or those in fresh/brackish water can probably stretch it a bit.

FWIW, my Wellcraft had Mercs sitting in seasonal brackish water and lasted 12 years before failure. YMMV

 

[guyerst]

Is ther much difference with the exhaust ports from the block between engine suppliers? I have a couple old Chris Craft 327s that had reman 350 blocks put in by the PO. The original 327 manifolds are still being used. Not sure about the risers... they are leaking a bit at the connections so they could very well be original also (1970).

Original or not... they need to go. I'm thinking I'd like to use the Crusader set-up. Assuming some extra plumbing work needed after the risers, are there any other roadblocks with this? Block to manifold should line up correctly, correct?

 

[UNIQUE_NAME]

my 427 fords have custom copper 1 piece riser/elbows. engine/manifold are closed system. any ideas on how long they may last?


i'm in salt water...


jim

 

[Jackman]

Maynard,

Try George at Boatfix.com. He has a lot of connections with this kind of stuff. Maybe he can help you out.

 

[Beckytek]

I called George when I was looking for the dogbones. He suggested having them custom made from stainless. Ron

 

[smoothmove]

Some pretty tough lookig risers

I called George when I was looking for the dogbones. He suggested having them custom made from stainless. Ron

Something like this? These are some serous looking solid stainless steel replacements for some old Chris Craft risers.
Eric

 

[Maynard Rupp]

Wow, I bet those cost a bit. I have been looking at osco products. They make an 8" and a 4" riser. In the photo it looks like I could bolt the 8" to the engine, then bolt the 4" to the 8", then bolt the elbow to the 4". i sent them an E-mail about doing that with their stuff. No reply yet.

 

[Beckytek]

Maynard, That is what the yard mechanics did with my engines. They work fine as long as you have enough room to fit. 3 of the 4 fit fine for my boat but the 4th one wouldn't pass the steps to my stateroom. You will have to get new hoses too due to the new exhaust path. Ron

 

[REBrueckner]

Wow...That exhaust riser in post # 16 looks incredibly sturdy....I'm afraid overkill.... I'd sure be concerned about the WEIGHT of that thing hanging off my exhaust manifolds...I note that on my old DD diesels there are supports for everything indicating to me that vibration stress is a real issue over time...

 

[REBrueckner]

Wow...That exhaust riser in post # 16 looks incredibly sturdy....I'm afraid overkill.... I'd sure be concerned about the WEIGHT of that thing hanging off my exhaust manifolds...I note that on my old DD diesels there are supports for everything indicating to me that vibration stress is a real issue over time...
Also, are those protrusions for hose connections in the upper end long enough to get a good grip....or two hose clamps on each???