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Exhaust manifold replacement interval

S

scott_duerring

Regular Contributor
What is the generally recommen

What is the generally recommended replacement interval for exhaust manifolds on FWC engines that are operated in fresh water? My Crusader 8.2s are going on ten years with the same manifolds. Replace or not?
 
I've had them last 20 year

I've had them last 20 years on FWC in salt water usage. Flaking rust on and near the exhaust ports will be the limiting factor. I haven't found any paint to stay on with the heat.
 
"Mine were ten years old when

"Mine were ten years old when I took them off (last week) and they looked pretty good. Mechanic said I should re-use them but, I'm replacing anyway. My boat is kept up river in brackish water, but used in salt. Also, my engine is freshwater cooled but, my manifolds are raw water cooled. Rule of thumb on raw water cooled (salt warter) is 3 - 5. I would think fresh water would be at or about the life of the engine..."
 
"I'm sorry, I was thinking

"I'm sorry, I was thinking risers when I said "rule of thumb is 3-5". Manifolds should be a long time, like diver dave said."
 
"risers: I tried to push rise

"risers: I tried to push riser life to 5 years. Some 20 miles offshore, my wife announces "what's that smoke?". My OEM Crusader elbow had completely and suddenly rust plugged, causing a length of 3" exhaust hose to go dry at cruise power. It put out a pretty healthy amount of smoke, that's for sure, and reduced the wall thickness on that piece of hose. Now, they get replaced at the 4 year mark. Luckily, my fiberglass muffler was cooled by the other side of the engine, or things may have gotten real exciting below deck..."
 
"Scott:

As indicated above,

"Scott:

As indicated above, you shouldn't have to replace them; the risers and elbows are different. The time will vary based on your environment and use. I was lucky a few years back and obtained some stainless steel elbows which have been very good.

Diver is right about the paint - best thing I've found so far is ceramacoat (sp?). The color changes in the high heat areas but it slows the rusting process a lot. Unsure of the cost-effectiveness in today's market."
 
"Thanks for the information, s

"Thanks for the information, so as I understand it, manifolds may last forever, but risers and elbows need to be replaced every 3-5 years in salt, quite a bit longer in fresh. Right? Was curious as to where you found the stainless steel elbows."
 
"Funny but my manifolds and el

"Funny but my manifolds and elbows do have paint on them that looks new. My water adapters had a hot spot where the Crusader Blue spray can paint had yellowed but after getting a bit more coolant there, a new shot of spray seems to be holding up quite well.

One place to check on stainless exhaust parts might be Stainless Marine in Florida... NOT cheap!

Watch out for that " forever ". It may catch up to you quicker than you think. Separating these parts just after a few years may prove difficult at best, despite stainless studs and anti-seize."
 
"My manifolds were about to be

"My manifolds were about to be reused for another season since all looked fine. It was when the riser stud snapped in the manifold that it became to time to call Osco. I drilled the stainless stud in the original Crusader enough to get a bolt extractor on it, but when the bolt extractor snapped off, it is now replacement time. I'm doing the one manifold now to get the rest of the season in, but over winter will be replacing the other three."
 
Scott:

The S/S risers came

Scott:

The S/S risers came from mercrusier. I was working for a guy overhauling outdrives & engines at the time so most anything was cost+5.

Rich: we used to remove 'crusty' fasteners with a "rosebud" end on the torch and a liquid called kano kroil. Had close to 90% success rate. The worst parts were the exhaust cover bolts on the inline 6 cyl outboards.
 
"Sounds real familiar Dave! Ha

"Sounds real familiar Dave! Had the same thing happen to me. Riser and elbow clogged up, pumped out dry exhaust, melted hose and muffler. Nasty smell from that melting exhaust hose! Took manifolds, risers, and elbows off and finally got them apart. I had a post on this problem before. Still would like to find a semi-easy way to seperate the riser from the manifold without cutting and breaking. The manifolds looked good but the rest was a block of salt and rust. Found Osco risers on-line at www.ebasicpower.com for a great price. Was told by some old timers that the Osco was a better part than the original Crusaders. Anyone had experience with them? Went ahead and replaced all the risers and elbows. Rather do it at the dock than 20 miles out. When in doubt, replace new!!!!"
 
"Mark,

I would have loved t

"Mark,

I would have loved to go stainless when I did these parts in November and this May but when I totaled the costs...well over 2000 PER engine. For that and a few dollars more, I could have had my hands on 2 used but VERY decent diesels. Of course the drives and a few other changes still made the change prohibitive for the residual value of my boat but the thought was there. For a few more scraped knuckles, I don't mind doing the work"
 
"Osco & Barr had a pretty

"Osco & Barr had a pretty good name in the aftermarket business when I worked at the shop. There were even discussions about them supplying certain OEMs with their 'excess capacity'.

I had the burn thru syndrome one morning. 42 miles into a 50 mile run to catch 100+ lb. bluefins. Never did find anything wrong with the cooling system. the concensus was an ice bag or something similar covered the raw water inlet. Besides that awful smell, the white and grey in the exhaust was a scary thing. Whole event was less than 30 seconds but took out both exhaust hoses right behind the risers. Temp warning horn never went off as I had shut both down.

I dug thru my papers - in 1997, i paid $735 for the four risers and the gaskets...I'd say Al's numbers, for today's market, are pretty reasonable"
 
"breaking apart the riser from

"breaking apart the riser from manifold: I'm no expert on this, but I am trying different methods. Last time, I used studs into the manifold, with stainless, fine thread nuts. I put the gaskets on dry. 4 years later, pretty much a rusty mess, but they did seperate fairly easily with a mallet tap. This time, i'm using very thin ultra-copper rtv on the gaskets, and grade 5 12 point bolts and copper washers. Jury is still out.."
 
"Aero Kroil ([url=""]www.k

"Aero Kroil (www.kanolabs.com I think) is some excellent stuff anthough expensive.

Barr 8" risers and elbows for one engine just cost me about $390 with the elbow mounting kit."
 
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