Remote Exhaust mixing elbow

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4 years 6 months ago #2383 by David Irwin
Remote Exhaust mixing elbow was created by David Irwin
Hello All,
I have a 78 Whitby with a Ford Lehmann Engine and the "mixing elbow structure" is 5 ft from the engine in the port side cockpit locker on the end of some HOT 2" pipe.
All spring I have been working on a project to cool my super heated engine compartment after adding 2/4" exhaust fans (one cumming in, one exhaust) did little to remedy the situation. I wrapped 20' of 3/8"OD tin lined copper tubing around the 5 feet of dry exhaust pipe and put a dedicated pump that takes raw water tee'd after the sea strainer and pushes it thru then goes overboard amidships. I will wrap all the piping the in 1" mineral wool pipe insulation (rated for 1000 deg) wrapped in aluminum sheeting (all the above from McMaster and Carr)
Murphy's 2nd law of ever exspanding work scope came the other over the weekend when afor mentioned exhaust mixing structure started leaking out of the blue. By crude estimates of previous owners tenure I would say its at least 10 years old at this point and I remember the surveyor telling me at purchase time that it was only a mater of time for all water injectors especially in salt water.
So my question is, has anyone had exsperience with these particular water mixing structures, where did you get it and about how old was the one you took out?. I know that I have seen pictures of water lift mufflers place on the generator shelf but I am a little weary of the amount of verticle lift needed and the back preasure generated. The piece looks like it was fabricated in a shop rather than manufactured so I was going to take it out and cross cut it a few times with a Portaband saw to see how the inside of it is constructed. Any guidence for this would be appreciated.

Regards
Dave Irwin
S/V Comfort
Boston MA

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4 years 6 months ago #2384 by Mark Popiel
Replied by Mark Popiel on topic Remote Exhaust mixing elbow
Here are two pics of part of the exhaust system for the Ford engine on my 1980 Whitby 42. The water comes down from the siphon break in a black hose and enters the exhaust just before the end of the insulated portion. The water and exhaust go to a Verna lift muffler which is obscured by hoses and the smaller generator muffler. The hose runs back to the transom. The previous owners had this custom built and it has lasted six years for me with no issues.


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4 years 6 months ago #2385 by Dennis & Lynn Pelletier
Replied by Dennis & Lynn Pelletier on topic Remote Exhaust mixing elbow
I have owned a 1975 Whitby since 2002 and it has a 101 HP Detroit Diesel 353 engine (the only one in a Whitby as far as I know). The boat and engine came with a remote mixing elbow in the port lazarette. I hated it for many reasons including the heat generated. The engine size dictated a 4" hot exhaust pipe and it made access to the port/aft part of the engine compartment nearly impossible. Another problem it created was that the pipe was attached to the engine with a flexible stainless steel section of exhaust pipe. This was done to prevent the engine vibrations from cracking the exhaust pipe. I don't know if the former owner had any problems with the flexible piece, but mine started leaking exhaust after about 2 years of ownership. I had it replaced and that one lasted about two years.
Before the replacement flexible pipe started leaking exhaust I experienced a reduction in power and RPMs which was finally traced to the mixer. This happened on December 31, 2005 as we were leaving Ft. Lauderdale for the Bahamas. It took a month to diagnose the problem, find a shop willing to fabricate a new mixer and get it installed at a cost of around $5000. It was during that Bahamas trip that the replaced flexible pipe started leaking exhaust.
Needless to say, I’d had it with my mixer and set about finding a mechanic who could and would replace it with something else, preferably a water lift muffler. After contacting several highly recommended marine diesel mechanics in St. Petersburg I found JR Hawk who was fascinated by the uniqueness of my engine and its history (the original owner was the CEO of Detroit Diesel). He agreed to take on the project and did an excellent job. The overall cost was about $8000, and was well worth it.
Here is a list of what was done:
• Design a new muffler and exhaust system capable of handling the 101 HP engine (this was the part most other mechanics were unwilling to attempt).
• Replace and relocate the generator water lift muffler to make room for the new engine muffler.
• Remove the existing exhaust pipes and mixer from the engine through to the exhaust hose that runs along the port hull from the port lazarette to the transom. (These pipes weighed 90 lbs. and their removal reduced my slight port list.)
• Fabricate a new stainless steel mixing elbow to be attached to the engine manifold. He actually made two, one as a spare. The other parts are available off the shelf.
• Run new plastic and rubber exhaust system to the port lazarette and connect to the existing port exhaust hose.
• Created a diverter to direct some of the engines raw water to the aft head sink thru-hull since there was more water than was needed by the water lift muffler to cool the exhaust.
• Install all of the above and hope it worked as designed.
• The system included drain hoses for both water lift mufflers (engine and generator) which are designed to be closed during engine operation and opened when the engine is shut down. This was to eliminate the possibility of water siphoning back into the engines.

That was in 2007 and the result has been zero problems since including on our Caribbean cruise from 2008 through 2011. The engine actually produces 2500 more RPMs than before which I believe indicates the exhaust is operating more efficiently. In addition the engine now runs in the rated temperature range versus running at 25° F under the rated minimum temperature. The net result of the exhaust replacement is a better performing and more reliable engine, less heat in the engine compartment, more room in the lazarette and better access to all parts of the engine compartment. The only negative is the engine exhaust noise is higher than before. This could be eliminated with the addition of a sound baffle which JR recommended adding, but I declined.

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4 years 5 months ago #2386 by David Irwin
Replied by David Irwin on topic Remote Exhaust mixing elbow
Thanks again for the input guys,
Tough to beat the advice of first hand experience.

Regards

Dave Irwin
S/V Comfort
Boston MA.

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