Need to Replace Exhaust Riser on Universal

[capngeo]

Originally Posted by ShipShape

crashkahuna, as a surveyor I am obligated to tell you that the reinforced PVC water hose on your wet exhaust is a danger to you and your boat. If the vessel is afloat and the seacock is not closed, IMMEDIATELY CLOSE YOUR ENGINE'S RAW WATER INTAKE SEACOCK, AND REPLACE THE PVC HOSE WITH APPROVED MARINE WET EXHAUST HOSE BEFORE STARTING YOUR ENGINE AGAIN. I also see other reinforced PVC water hoses in the picture, if they are part of the engine system then also renew those with approved hoses at the same time.

Surveyor hat off.

Replacing my engine's exhaust elbow is so close to the top of THE LIST that I'm already looking into it. Given that this part is doomed to corrode, and that a failure has the potential to sink a boat and kill people with CO poisoning, I do not understand why replacements are not readily available. Nigel Calder usually has good advice and in his Marine Diesel Engines book he says that, "The elbow is frequently custom-made and hard to replace, so you should inspect it annually and carry a spare on board." Given that it looks like I'll have to fabricate my own exhaust elbow I intend to make two. If it is really fun I'll make three.

The main reason I have not considered stainless is the issue of drilling and tapping a hole for the water injection nipple - George how did you handle that part of it? What grade stainless did you choose?

Just threading the nipple in is a recipe for disaster! The water injection nipple either needs to only go into a water jacket OR continue downstream past (below) the level of the inlet. Failure to do this will either allow water or spray to possibly follow the manifold back to the engine, corrosion or hydrolocking being the result.

To answer your question... I weld it in

To the OP (or anyone else on the forum): If you need help with a mixing elbow and can't find a local shop to fab it... let me know. Attached are pix of one I just finished for a genny

[Chief Engineer]

Nice work!!!!

[crashkahuna]

Good eye. I bought this boat recently and surveyor also noticed that incorrect hoses were used. Replacements are in the works.

[marc2012]

There was a thread either here or sailnet re.risers.The opinion was ss was not as good as black or galv in salt water.Don't know but worth ckng.marc

[crashkahuna]

Yeah looks real nice. Can you explain more about the inlet nipple going into a water jacket? (ie what is a water jacket in this application-trying to visualize.)

Does going downstream past level of inlet mean the water exits the nipple below the level where the nipple first enters the riser? Does it matter if inlet nipple enters vertical or horizontal? Thanks.

[nknowland]

I am also replacing my exhaust elbow (cast aluminum from Westerbeke) and plan to replace the riser as well. I have the replacement from Westerbeke but at $300+ can I just as well use a black pipe elbow with a T fitting that could be fabricated by a plumber or marine shop?

It sounds like black pipe is better than galvanized. I am concerned about the gassing of the zinc with galvanized pipe. My existing riser is covered with a woven material and don't want to risk removing on the chance that it could be asbestos. I plan to wrap the new riser with fiberglass manifold wrap Fiberglass Tape Manifold Exhaust Wrap .

There was a recommendation to use bronze nipples but is that for direct exhaust elbow to manifold arrangement vs. manifold to riser pipe then exhaust elbow? What about sealing the threads with a high temp furnace cement vs. teflon past or tape?

I may also replace the hose to the waterlift muffler and the muffler while I am at it.

Any other suggestions?

[capngeo]

Originally Posted by crashkahuna

Yeah looks real nice. Can you explain more about the inlet nipple going into a water jacket? (ie what is a water jacket in this application-trying to visualize.)

Does going downstream past level of inlet mean the water exits the nipple below the level where the nipple first enters the riser? Does it matter if inlet nipple enters vertical or horizontal? Thanks.

This is one of those picture is worth a thousand word situations!

If you use a simple "T" to inject cooling water, there is nothing to stop water from entering the exhaust port of the head (or turbo) when the engine is shut down or overcranked (as when purging air).

A proper mixing elbow is essentially a pipe within a pipe; the water is injected into the space between the pipes. The inner pipe which carries the exhaust gasses is shorter than the outer pipe which is connected to the exhaust hose. The exhaust becomes "wet" only where the inner pipe ends. This point is ALWAYS well down "hill" from the engine manifold.

I'm on my phone, but if it still doesn't make sense, I'll draw a diagram when I'm next on a computer.

[perchance]

Originally Posted by Chief Engineer

You can make the entire thing out of black iron pipe....for the water injection you will need a TEE that is 1 1/4 x 1 1/4 x 3/4 or 1/2......any plumbing supply store will have that.

No need to buy an overpriced water injection elbow.

PM me if you want more info

I knew I had seen a elbow in black iron similar to a water injection elbow but couldn't remember where till I looked up at the ceiling at my grandsons hockey arena and there it was on the sprinkler system.

[GordMay]

Originally Posted by perchance

I knew I had seen a elbow in black iron similar to a water injection elbow but couldn't remember where till I looked up at the ceiling at my grandsons hockey arena and there it was on the sprinkler system.

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