Diesel Engine Help!

[Jack]

Yesterday I went to the boat to check on things. As it has been about a month or so since I ran the engine, I cranked it up, only to sense that the engine was spinning rather than firing as it normally does. Typically, 3 seconds on the starter and it fires right up. This time I had to run the starter several additional seconds and I could tell it was sort of starting…strange, but it did start and ran for a good hour. I searched to boards for similar symptoms last night but did not find anything.

Today, I started it up, and it started as normal. However, after about 30 minutes, I noticed my bilge pump come and it was really shooting a stream of water, not at all normal, I pulled the bilge hatch and it was flooded, I shut the engine off and bailed it dry. The engine compartment looked as it someone have hit it with a hose. I tried to restart and the engine acted as the previous day, but I got it going only to quickly fine water gushing from the mixing elbow. On examination the pipe (covered in asbestos) has completely rusted away.

I have two questions. 1) Obviously the pipe has been slowing rusting over the past 7 years (300+hours) when we had it last replaced (in reading the boards, I now know I should have been checking this every few years). If this area was leaking, exhaust gas, would it have caused the engine to start/act as described above?

2) I have not pulled the elbow (which appears fine from the exterior, how long should it last (it was replaced 7 years ago (300+hrs.), nor the pipe from the exhaust manifold to the elbow. There is much debate as to the use of straight black iron or s.s. for replacement. What is the latest thinking?

My thanks to all of your for you advice and counsel.

[Paul D.]

Jack,

I just replaced my exhaust elbow and used galvanized steel as that was what was on there. I am in fresh water though so I cannot tell you what is best. Zeida just did hers with SS then I think redid it with steel for some reason, do a search on her posts and you will find some good info on this. She is on a CD 33 and in Florida waters too.

I had mine welded up at an auto shop for $100 and installed it myself. One tip I had from several sailors who seemed to have learned the hard way was to use the ultra copper gasket sealer to join the manifold piece to the motor. I did and it worked well. I get just a small drop of antifreeze out of the joint. But others said they got poor sealing and short durability with any other gasket sealant.

Best of luck,
Paul

[Jack]

Paul,

Thanks, I did find a good deal on the board about the use of galv. steel vs. black iron vs. S.S.. I could not find the post you noted.

I'll probably just rebuild in heavy wall black steel pipe and fittings.

However, my main question still remains, would an exhaust pressure leak cause the engine sysmptoms I experienced. It seems to me that it was probably leaking pressure prior to it finally breaking from the water injector.

Thanks again for your advice.

[Oswego John]

I'll probably just rebuild in heavy wall black steel pipe and fittings.

However, my main question still remains, would an exhaust pressure leak cause the engine sysmptoms I experienced.

Hi Jack,

By any chance, do you have a compression release on your engine?

Most exhaust systems have been engineered for maximum efficiency. As I understand it, a leak in a dry exhaust system will produce extra noise with little or no loss of engine efficiency. It is a restriction or clogging in the normal flow of exhaust gasses that will produce back pressure and have a negative effect on the engine's performance.

Normally, you could consider a marine diesel's exhaust a dry system from the exhaust manifold to the mixing elbow. Cooling water is introduced into the exhaust system at the mixing elbow. The hot engine exhaust, when combined with cooling water, transforms the system into a wet exhaust system. The coolant tempers the heat of the exhaust for both bodily safety reasons as well as fire prevention reasons.

If the sealed area of the wet exhaust is compromised, instead of all the water being expelled out of the transom pipe, the coolant will enter the hull through the compromised area of the defective pipe system. In some instances, coolant water can backflow into the dry exhaust section as well as into the exhaust manifold and block.

In selecting the material to be used for constructing an exhaust system, I'm not going to dwell on the merits of one metal over the other. Black iron, galvanized, stainless steel or bronze, they all will do the job. Threaded, mig welded or brazed, when done properly, they all perform well.

Several factors affect the choice of material. The main factors that I consider are availability, ease of assembly and cost, not necessarily in that order.

For me, the choice narrows down to black steam pipe. Black pipe fittings are readily available in well stocked hardware stores, plumbing and heating supplys and home supply stores. Nipples and close nipples are available in usually 1/2" increments. Also ells and unions, too. Mistakes aren't costly as unused parts can be returned or exchanged.

Fitting up is relatively easy, piece by piece. Especially on the dry section of the exhaust, I like to use black, high temp, pipe fitters dope on the threads. It's okay to use teflon-base dope on the wet section.

Most exhaust systems break down from the inside. Most manufacturers and repair shops won't go to the extra bother to do what I learned to do when following government specs. Before pipe assembly, thoroughly clean any dirt or cutting oil from all surfaces of the pipe and fittings. Then swab the interior of all components with one or more coatings of two part epoxy paint. After final assembly, it wouldn't hurt to do this to the exterior of the system, also.

Another reason that I favor threaded black steam pipe is because if I should need an oddball length of pipe nipple, if it isn't readily available off the shelf, Ace Hardware will fabricate what i need and only charge $1.00 per cut or per thread.

I don't use galvanized, first of all because it costs more, but more importantly, when you cut and rethread it, the new threads aren't protected. The galvanizing on the outer surface is destroyed and you now have the same metal as black pipe.

It's the same idea when you go to weld Galvanized pipe. For a proper weld, the galvanizing should first be ground off. When welding galvanized metal a toxic gas is produced. The finished weldment loses it's galvanized protection.

I know that this is getting long so I'll just say one more thing.

Ultra Copper is an excellent gasket compound. I'm a Permatex kind of guy. No matter what you use, if the flange faces aren't perfect, if there is any warpage, it will be very difficult to produce a perfect seal. One of the things I have done is to paint the surface(s) of the flange with Prussian Blue engineers ink. Then lightly, very lightly, draw file the surface with a smooth cut metal file. Any minute imperfections will readily appear where the blue is removed.

Good luck with whatever method you go to.

O J

[Al Levesque]

OJ,

How do you introduce the cooling water? I assume it has to enter the outbound side of the elbow, or does it matter? Do you drill and tap for the connection or are there tees that can be used? How much drop does there need to be after the elbow?

I've looked for sites that might answer these questions but there seems to be little information on them.

Thanks for any answers.

[Jack]

John,

A couple of points of clarification and a few questions for you. First, I have a 13 hp Westerbeke, which if I'm reading the mannual correctly allows the exhaust elbow to screw directly into the exhaust box. It appears that the elbow (the threaded pipe), prior to the water injected exhaust part). It seems that the pipe finally gave way completely (rusted through) at the water injector exhaust.

My thinking was that if this was leaking exhaust pressure, that may have creaated the action of easily cycling when I went to start. This enjine always start on the 3-4 compression stroke (3 seconds tops, even in colder weater - I'm in Florida).

First day when I layed on the starter I could tell it was firing, but not like normally. Let off the switch and it ran fine. Humm

Second day, started right up as normal. Only later (after aboutt 30 min running) did I notice the bilge pump shooting a heavy stream. Looked below and noticed the bilge flooded. Shut the enjhine off before I could see where the water was coming from. Once bailed, resarted (acted as it did the previous day, but started rightt up. I ran below and saw the extreme strap coming from the gap between the exhuast injector and the exhaue elbow. The asbestos wrapping might have been the only thin keeping it togehter.

Would this lack of exhaust back pressure have caused the strating as I described?

I've been speaking with several marine exhaust dealers in Florida (all of whom would like to weld me a new part). All of them claim SS 316 is the only thing to use. Yes, costs more but will last many many years....so they claim. I can get SS 316 pipe and fitting (schedule 80) for a reasonable price.

Finally, is black steam pipe the same as black iron? I can find black iron, but not black steam pipe.

Your thoughts and suggestions are greatly appreciated. Thanks

[Oswego John]

OJ,

How do you introduce the cooling water? I assume it has to enter the outbound side of the elbow, or does it matter? Do you drill and tap for the connection or are there tees that can be used? How much drop does there need to be after the elbow?

I've looked for sites that might answer these questions but there seems to be little information on them.

Thanks for any answers.

Hi Al,

When I used to build or repair these systems I didn't always go according to any book. Some might have called my methods unorthodox but they were individually designed according to the available room to work in.

The main thing was that I included a vacuum breaker or anti-siphon at the apex of the system. As you mentioned, the cooling water enters on the outboard side .

You can drill and tap black pipe but it might prove to be a hassle drilling and tapping SS. I often used street ells for water entry. Tees are available and can be bushed down to accept smaller bore nipples. You don't want water to enter the engine exhaust manifold by either gravity or siphoning.

When the engine is running, exhaust pressure prevents water from possibly backing into the manifold and block. If the engine isn't running, water isn't being pumped into the system.

I would suggest that you use all available drop as possible. This would include from the top of the anti-siphon loop down to the point of exit of the exhaust. In my mind, this drop would help prevent any possibility of, when sailing, a crashing, following sea from washing into the exhaust pipe and entering the dry exhaust section.

Good luck,
O J

[Zeida]

Hi, Jack... I replaced the old, corroded riser (metal unknown to me at that time) and a professional exhaust company built me one to the same exact proportions, but in Stainless Steel. They also said that it is the industry's standard in the latest years. The SS riser is not as heavy as the iron one, much cleaner, it also came with a fiberglass/canvas cover, very practical and easy to remove when you have to inspect things in there. I have also used a bronze riser made by me using different fittings, but it was too cumbersome and super heavy! So I have reverted to my SS. It does NOT last forever though, and mine developed some tiny holes in the mixing elbow (the nipple where raw water comes into the muffler from the heat exchanger). But I have since had it fixed, and is back on the boat. I do make it a habit of every 6 or 7 months remove the hose and check it out to make sure it is not clogged, etc. I do prefer SS over anything else. If you still have the original, best thing to do is have an exhaust company build you a new one. Make sure the welds are far and few, and as good as they can be.
Good luck.

[Oswego John]

John,

It seems that the pipe finally gave way completely (rusted through) at the water injector exhaust.

My thinking was that if this was leaking exhaust pressure, that may have creaated the action of easily cycling when I went to start. This enjine always start on the 3-4 compression stroke (3 seconds tops, even in colder weater - I'm in Florida).

First day when I layed on the starter I could tell it was firing, but not like normally. Let off the switch and it ran fine. Humm

Would this lack of exhaust back pressure have caused the starting as I described?

[O J] For the engine to kick over, it needs three major things, air, fuel and compression. The other day, I asked you if your engine had a compression release. When there is a reduction in compression, the engine will spin much faster when turned by the starter. Although the engine is spinning faster, low compression keeps the air/fuel mix from detonating. When compression rises to operationalpressure, the air/fuel will fire. I could be wrong, but I don't see how a water or exhaust leak would cause the engine to spin a lot faster than normal. My first guess would be a temporary drop in compression.

I've been speaking with several marine exhaust dealers in Florida (all of whom would like to weld me a new part). All of them claim SS 316 is the only thing to use. Yes, costs more but will last many many years....so they claim. I can get SS 316 pipe and fitting (schedule 80) for a reasonable price.

[O J] Stainless steel is as good as any metal to use on an exhaust system, better than others. SS 316 and 316 L (low carbon) are the alloys best for marine use. I'm glad that you are choosing pipe. Sometimes they fabricate a system using tubing which has a much thinner wall than hardwall pipe. The use of schedule 80 pipe will last a lifetime. It's what they use in nuclear power plants.

Finally, is black steam pipe the same as black iron? I can find black iron, but not black steam pipe.

Your thoughts and suggestions are greatly appreciated. Thanks

[O J] I'm guilty, got egg on my face again. It's a matter of semantics. Black pipe, black steam pipe, black steel pipe, all the same animal.

Just be careful of one thing. Some cheaper imported, junk, black pipe is rolled. It has a thin welded seam along its length. Stay away from that garbage. I've seen it pull open when trying to cut threads on it.

Good luck with your project.
O J