Rough Elbows

Maintenance Q & A — June 2004
By Capt. Ken Kreisler

Rough Elbows
Why paying attention to an exhaust elbow is important, a teak cleaning tip, and more.
 More of this Feature
• Exhaust elbows, and more
• Teak cleaning tip, and more
• PMY Tries... Sea Hawk Paint Stripper

 Related Resources
• Maintenance Q&A Index

This is my first diesel-powered boat, and I understand I should pay special attention to the engine’s exhaust elbows when doing routine engine checks and maintenance. Why? R.R., via e-mail
After exhaust leaves the combustion chamber and passes into the exhaust manifold, which is usually water-cooled, it passes to the elbow. It’s elevated and shaped like a reverse sink trap to ensure that water cannot make its way back into the engine and cylinders. If this happens, the result is hydro-lock: Because water does not compress, the pistons will be unable to move, possibly resulting in bent connecting rods or worse.

There are two basic reasons to keep a close eye on this part of your engine. The first is that because it is located so close to the exhaust manifold and not water-cooled, the exhaust elbow is one of the hottest places in the exhaust system. The other is that although salt water is injected here, there is no sacrificial zinc to protect it. Hence this is the spot with the highest potential for corrosion and usually the first part that needs to be replaced.

I am thinking of installing a 1,200-watt power inverter on my 35-foot boat. I have an old shore-power cord I’d like to cut down and plug the male end directly into the inverter and the other end into a shore-power outlet. Will this damage anything? C.E., via e-mail
This is not a good idea. Doing so violates numerous electrical safety codes, both for onboard and on shore, and might place you in danger of electrocution.

Second, it may not provide proper neutral-ground bonding. Neutral-to-ground bonding must be at only one point—the shore-power source when plugged into shore power or the onboard electrical system when operating independently. This is a safety feature that should be built into all craft using shore power.

Then, of course, the day will come when you plug into shore power without unplugging the inverter. If you’re lucky, a fuse or breaker will blow before the shore power supply does; if you’re not, the inverter will go up in smoke.

The long and short of this is, get a certified electrical installation technician or engineer to correctly hardwire your inverter to the shipboard supply. If you want more information on this or related inverter matters, check out the Xantrex Web site at

Next page > Teak teak cleaning tip, and more > Page 1, 2, 3

This article originally appeared in the May 2004 issue of Power & Motoryacht magazine.

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