Rotted Exhaust Pipe

[vabiker23518]

On my first run this spring, I noticed much more smoke in the engine compartment; I thought it was from the oil filler tube, so I purchased and installed the Indigo PVC kit and installed it today. Upon starting it ran well, but soon I noticed smoke and the exhaust wrap was wet and dripping. After shutting down, I removed the wrap and saw the pipe was "rotten"...with several holes that were letting exhaust and water out.
My question is, is there a standard exhaust pipe? This starts at the back of the exhaust manifold, and is bolted to it with two bolts. Its square, and about 18" in length, and runs from the engine at a 45 degree angle. A round heavy rubber exhaust line attachs to it and runs to a lift muffler. There are water inlets and outlets at the top and bottom. Realize a picture is worth a thousand words, but I didn't have my camera with me. Any ideas?

Thanks,

[sunnnnseeeker]

I recently built a new exhaust pipe system with 1 1/4 inch galvanized pipe all purchased from Home Depot. Picture attached. It is in my boat and working great.

[Don Moyer]

I'm thankful your system is working to this point, but unfortunately
(depending somewhat on the configuration of the rest of your exhaust system)
you are somewhat vulnerable to engine cooling water backing up into the
engine.

If you check the attached sketch of a typical exhaust system, you'll see that
you have essentially inverted your hot section vertically from the sketch,
which will keep some amount of engine cooling water trapped in the low
section at all times. Any amount of cranking of the starter will have
additional engine cooling water pooling to within several inches of running
back into the exhaust manifold, even if everything else in the system is
downhill to the back of the boat.

To prevent hydrostatic flow through the engine from filling your exhaust
system while the engine is not running (and possibly flowing back into the
engine depending on the rest of your system), you will also have to be sure
to keep the raw water through-hull valve closed at all times and/or depend
on a perfectly functioning anti-siphon valve in the engine cooling water
hose from the manifold to your water entry fitting.

Finally (and sorry to sound so negative) the tendency for engine cooling
water to back up ahead of the water entry fitting will also add a small
amount of additional exhaust back pressure, though probably not enough to
cause an immediate problem.

Don

[tenders]

Is galvanized pipe ok for exhaust systems? I seem to recall something about the heat vaporizing the zinc causing poisonous fumes, but I can't find anything to back this up.

[sunnnnseeeker]

Don,

Thanks for notice about water backing up into the exhaust/engine and the diagram of the exhaust system. The photo I posted is opposite orientation of the way the hot pipe section is installed. I do have the bottom of the U installed so it is the highest point.

tenders: Don's diagram does note "galvanized" pipe. I don't think it gets hot enough to cause any vaporizing of metal.


Nathan

[gary gerber]

Three years ago I replaced my exhaust system on my Morgan 33. I have an article on the installation in the current issue of BoatUS DIY magazine. Maybe it will be of some help.

[vabiker23518]

Appreciate everyone's concerns and advise. Luckily, I was able to get the pipe off the manifold with no broken studs or fingers. I will make a galvanized pipe exhaust tomorrow using the drawing and a couple pics of others that I found on the board. Will take a pic of the old pipe (someone went to a lot of trouble to weld round pipe to square pipe) and the new pipe for demonstration. Thanks again, Wayne Columbia 8.7

[blackdove]

It is highly unlikely that, without melting the alloy used in A4's, that there will be any zinc fumes from galvanized piping. I would anticipate that on the first running of the engine following the installation of the new exhaust system you would experience some "burning" of the oils used during the extrusion process. Just keep everything opened up and run a fan if need be. Thank you.

[vabiker23518]

Heres the picture of the rotted exhaust pipe, and the new gal pipe, with insulation installed in the boat!
Thanks again to all for the help,
Wayne Columbia 8.7

[vabiker23518]

Hope these are easier to see...they have been resized.
Thanks,
Wayne

[bayareadave]

I too fabricated an exhaust out of galvanized pipe (http://www.moyermarine.com/forums/showthread.php?t=1430). FYI, I have read in a couple of places (including a post from Don I think), that black pipe is better. I have since learned that black pipe is iron pipe, and is more resistant to corrosion than galvanized, especially in salt water. I didn't see much of a selection of black pipe at my home centers, but perhaps a good plumbing store would have them.

[sunnnnseeeker]

You did good on your pipe. Both galvanized and black pipe are made from steel. Thier surfaces are different do to the manufacturing process. The zinc coating on galvanized pipe (which the black steel pipe doesn't have) is designed to reduced rust and corrosion. Notice all the handrails, guardrails and poles in our country that are out in the weather made of galvanized steel. Black steel pipe has a natural oxide scale on its surface but this, after a short time, is basically unprotected steel, subject to rust and corrosion. In either case the pipe you installed is going to give you many many years of service. Enjoy your sailing!

[bayareadave]

Good to know my galvanized pipe is going to last!

[gary gerber]

Several years ago I replaced my complete exhaust system, it was featured in a recent article in BOATUS DIY magazine. page 59 of issue #2 2008. I utilized numerous Moyer components however due to space restrictions I used a Vetus water lift muffler instread of the traditional pot muffler.

The article explains all the parameters and solutions. My sailboat is a 1970 Morgan 33 cruising sloop. Good luck!