Kirby, I don't have any pictures to post on the CHB website, nor the old

Ron Jones wrote:
     snip......"On a recent trip the port exhaust hose burned through

Kirby, I don't have any pictures to post on the CHB website, nor the old elbow. However, the "shelf" in the Lehman exhaust elbow is easy to see. If you look up the "hose end" of the elbow, at the top you will see a flat shelf that acts as the diffuser for the incoming cooling water. This is what rusts away after a time. If it perforates, not only could you experience hot spots and potential burn-through of the exhaust hose, there's also a risk that, upon shutdown, some of the residual water in the system could flow backwards (forward in the boat) in the elbow and partially fill #6 cylinder, if the engine happens to stop with the #6 exhaust valve open. I'm sure you know how serious a hydrolock can be, but that's what may happen the next time you try to start the engine. Not trying to scare anyone, but as the old saying goes,"an ounce of prevention.........." Also, I have a temp sensor switch on the inboard side of the elbow which is connected to an alarm on my master warning panel. This will tell me if I lose water flow. Since my shelf never perforated (until I "screwdrivered" it, I don't know if it would alert to this failure. Andy Clark ANTARES CHB 34 Homeport, Everett Washington ----- Original Message ----- From: "Duffy, Kirby (TEM)" <kduffy@guidant.com> To: "'Andy Clark'" <slowboat@mindspring.com> Sent: Wednesday, March 14, 2001 9:58 AM Subject: RE: Lehman Exhaust Question > Andy, > Is there any way to attach some pictures in the CHB site of the old > elbow, what the shelf looks like, where you would try the 'screwdriver > test'. Did you ever try taking any external temp. readings on the elbow. > > Kirby > > 1979 34' CHB Tri-cabin > "Anteak" > Long Beach, Ca. > > -----Original Message----- > From: Andy Clark [mailto:slowboat@mindspring.com] > Sent: Tuesday, March 13, 2001 8:39 PM > To: twl > Subject: TWL: Lehman Exhaust Question > > > Ron Jones wrote: > snip......"On a recent trip the port exhaust hose burned through at > the end of the > > elbow. Engine temperature was normal." snip... > > --------------- snip........................Is the diffuser shelf inside the elbow rusted through? You'll > need to remove the elbow to check this. If it is, even though you are still > getting good water flow, the water is falling directly to the bottom of the > exhaust passage and the hot gasses are passing above it, again, causing the > rubber hose to burn through. Anyone with a '70s or 80's Lehman should check > this shelf yearly because of this age-related deterioration. Even if the > shelf looks good, give it the "screwdriver test". That is, try to drive a > screwdriver through the shelf using sharp raps from a hammer. Sometimes the > shelf looks good, but is rotten with corrosion, just waiting for the right > (wrong?) time to perforate.snip................