Exhaust Elbow

Hello to all:
I searched all of the exhaust elbow posts and think I know the answer to my question, so I'll ask it anyway. Engine has been running hot so I have replaced all of the raw water parts from the strainer to the exhaust elbow. Ran the boat Saturday and the overheating is still with me.*My guess is the elbow is original equipment (1993) and has never been replaced, so there may be a flow restriction at this point. Thats all I have left to replace, I think. Any help or ideas? Thanks.

Mike

Baton Rouge

Gulf Comanche wrote:I searched all of the exhaust elbow posts and think I know the answer to my question, so I'll ask it anyway. Engine has been running hot ...

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Has the engine itself been running hot or do you base that on the discoloration shown*near the exhaust elbow?

If the coolant and lube oil temperatures have been normal and all you have is the discolored paint I would say you don't have any problem. The discolored area is an uncooled portion of the exhaust system. The brown parts don't have any contact with cooling water so the paint is naturally going to get toasted. You can see it has been cool until just aft of the water outlet from the manifold and is cool again where that water is injected into the exhaust stream. Between those two points is very hot exhaust with no cooling water in or around it.*

If nothing else, that area is supposed to be covered with a heat shield or blanket as a safety measure.

Agree with Rick, but IMHO an 18 year old shower head, even if not causing the overheat, has done its job well and needs retirement.

sunchaser wrote:an 18 year old shower head, even if not causing the overheat, has done its job well and needs retirement.

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*It looks like it still works pretty good but you are right, at $100 to replace it has only cost about $5 a year.

I would take a look at the rubber exhaust hose too. It is easy to tell if it has been overheated - it will look blistery inside*- and if it is burned it will fail when you try to remove it. Replace it with a section of high temp silicone bump tube for longer life. This will also let you look at the inside of that elbow. If you take the elbow off at the attachment plate on the manifold you should be able to see if there are deposits collected in the area below the water outlet. Judging by the paint, there might be. Just scrape them out and flush the water side before using a new gasket to replace the adapter.

Don't forget to factor in the cost of the new flanges, the threaded parts that bolt on to the aft end of the manifold. I couldn't find them for less than $300 a pair. Ended up having them fabricated locally by a friend for materials and the cost of a nice dinner out.

Rick:
I'm not basing this on the color of the elbow but on the temp gauge running higher than before and the overheat alarm bell sounding. I also did not mention that the exhaust manifold has not been replaced and plan to replace this also. With that done, the entire raw water circuit will have been replaced. The engine water pump and anti-freeze have also been replaced. Thanks.
Mike
Baton Rouge

I guess I*misunderstood what you were asking then ... now I'm not sure that*you were asking something.*

Keep throwing parts at it though, something is bound to happen.

Mike, is that a Perkins 4.236? If so, brace yourself for the manifold cost. I had to order mine from Perkins...$1600 is my best recollection.

I heard one should replace ferrous elbows every 2 years and my experience w my previous boat suggests that to be a good rule. But the elbow for the little Yanmar was inexpensive. I got a 100% SS high rise exhaust elbow from National Marine Exhaust in Marysville Wa for $750. Should last almost forever.

Al:
$1600 at Trans Atlantic is correct, thus I am re-thinking the exhaust manifold replacement. I'll take it apart Saturday and see if I can clean it out.

Rick:
I suppose my question is this: Would a clogged up exhaust manifold or elbow cause the water temp to rise? I say it would but wanted another opinion before throwing too many parts at it.
Mike

RickB wrote:
*

Keep throwing parts at it though, something is bound to happen.

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*Don't know why, but that crack me up.

SD

nomadwilly wrote:
I heard one should replace ferrous elbows every 2 years and my experience w my previous boat suggests that to be a good rule. But the elbow for the little Yanmar was inexpensive. I got a 100% SS high rise exhaust elbow from National Marine Exhaust in Marysville Wa for $750. Should last almost forever.

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*I can't say that ferrous elbows should be replaced every 2 years but they are definitely maintenance items.* We had a Northern Lights 5kw gen set that we changed every 500 hours on our schedule after losing 2 at around 600 hours.* I lost*a Perkins 4-108 because of a bad exhaust elbow.* We currently have SS on the generator and engine and I still inspect them every 2 years.* Call me paranoid, but it's easier to do the inspection/repairs when it's convenient.

Also check for bits of impeller and bits of zinc blocking narrow passages.

I finally located the problem in the cooling system; the small port in the exhaust manifold where raw water exits to go to the exhaust elbow was about 90% plugged with rust particles, and the elbow itself was pretty well shot. Cleaned the manifold, replaced the elbow with a new one, and all is well. There was always steam coming out of the side of the boat where the raw water exits, I thought this was normal. Its not, no steam now, just lots of raw water. I got real lucky to not have burned up the engine, just wish I had checked that end first instead of replacing heat exchangers etc.

I'll file that one away for the future. You might have saved someone else a big engine repair bill!!

Thanks for the update.