What is the Advantage and Disadvantage of marine exhaust hose

How are Newer Catalina 27's Designed?

How are the newer Catalina 27's designed? I'd suggest just changing what is needed to match the lastest Catalina 27 design and not more (i.e. if it ain't broke, don't fix it).Catalina has done a marvelous job of improving their boats every year, albeit the 27 is no longer made, how was the last of the 27's designed (excluding 'walk-out' transom if any)?Have you reviewed the International Catalina 27 Association's website's 'technical information' and posed the same questions to their tech writer (http://www.catalina27.org/)?Have other Catalina 27 owners 'fixed' the problem the same way?Would not the 'back pressure' issue also be of concern within the 'water lift' muffler since it will experience the 'under water exhaust exit pressure?What does 'water lift' muffler instructions/requirements indicate about the back pressure of an 'underwater' exit?If diesel engines have no problem with 'back pressure', why do all motor vehicles with diesels have much larger exhaust/tail pipes?Are you sure the problem is a design issue and not just a prop/prop alignment/prop shaft length issue?My Catalina 30 can, with a following sea, when running near full throttle, periodically immerse the exhaust. However, I believe I notice it does it less since I had the prop's blade alignment/pitch checked and re-trued.How bad is your port stern 'walk' in reverse? If it is excessive, the prop pitch could be off, or one or more blades out of 'sync' with each other, causing the 'slapping' effect which caused the port stern-walk, and cavitation.I have also read that if the prop creates lots of 'cavitation', it actually causes the stern to sink down, possibly due to the air bubbles 'hole' created by the cavitation.By the way, on my 30, with a Universal 3 cylinder M25XP, whereas it does have a fiberglass water lift muffler, the rubber exhaust hose does not do a 'loop' on the way to the stern, but it does run high along the port side, just under the rub-rail, on its way to the middle-stern exhaust exit with flap (which is about 5-6 inches above the water when the boat is at rest).I would also echo "JC on Bainbridge's" comment about above the water and visible exhaust exits. I find it very easy on my boat to view the exhaust and verify water is mixing with the exhaust so I then also know my raw water system is working correctly.However, I also installed a neat water flow alarm in my raw water circuit just before the anti-siphon valve, which is just before the mixing elbow and then the water-lift muffler. If my impeller were to fail, of I were to forget to open the thru-hull valve, it sets off my cockpit engine panel alarm (wired it to the 'oil pressure' switch so that either will set-off the panel alarm). It is from Aqua-Alarm and in case your interested, here is the link: http://aqualarm.net/Hope this helps...

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diver dave said:

I would think those options would both be inferior in reliability/maintenance to an insulation wrap and passive venting.

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You would think. In an earlier life, I was a delivery skipper and delivered about 20 Nordhavns to various destinations. They all had massive A/C blowers to evacuate exhaust heat. I personally never experienced a failure but my understanding is sisterships are severely handicapped in the event of a blower failure.

Another example: Seahorse-built Diesel Ducks are wet-exhaust. They didn't start that way. Originally, the owner of the Seahorse yard wanted dry stack as he felt it made the boat more marketable as a long distance trawler (and I'm sure George Buehler, the designer, spec'd it). Hull #1 was brought on it's own bottom to San Francisco where I met the owner and spent a few hours with him where I gave him some docking tips (not a tremendously experienced owner, and not a lot of docking on the passage from Hong Kong). He described that, during sea trials, Seahorse just could not get the exhaust stack and engine room cooled. Eventually they gave up and converted to it to wet exhaust and punched the exhaust out the side of the engine room instead of leading it aft to exit the transom. Granted its been over 15-years since I talked with the owner of Seahorse, but at the time, he'd give up a child before he'd install another dry stack.

I'm not knowledgeable in the design of a dry stack so my experience is observation only. But it's first-hand observation, not dock-chatter. There appears to be more to a dry stack than just busting a hole in the roof and overturning a bucket on the stack to keep the rain out.

Personally, I like the idea of a keel cooler with a wet exhaust, though I was initially leery. The last Willard 40 was built for an exec of Willard Marine, and he had it built exactly that way. I accompanied he and his wife on a Baha Ha Ha from Long Beach to La Paz (~ nms or so) in or so, and I liked the setup a lot.

You would think. In an earlier life, I was a delivery skipper and delivered about 20 Nordhavns to various destinations. They all had massive A/C blowers to evacuate exhaust heat. I personally never experienced a failure but my understanding is sisterships are severely handicapped in the event of a blower failure.Another example: Seahorse-built Diesel Ducks are wet-exhaust. They didn't start that way. Originally, the owner of the Seahorse yard wanted dry stack as he felt it made the boat more marketable as a long distance trawler (and I'm sure George Buehler, the designer, spec'd it). Hull #1 was brought on it's own bottom to San Francisco where I met the owner and spent a few hours with him where I gave him some docking tips (not a tremendously experienced owner, and not a lot of docking on the passage from Hong Kong). He described that, during sea trials, Seahorse just could not get the exhaust stack and engine room cooled. Eventually they gave up and converted to it to wet exhaust and punched the exhaust out the side of the engine room instead of leading it aft to exit the transom. Granted its been over 15-years since I talked with the owner of Seahorse, but at the time, he'd give up a child before he'd install another dry stack.I'm not knowledgeable in the design of a dry stack so my experience is observation only. But it's first-hand observation, not dock-chatter. There appears to be more to a dry stack than just busting a hole in the roof and overturning a bucket on the stack to keep the rain out.Personally, I like the idea of a keel cooler with a wet exhaust, though I was initially leery. The last Willard 40 was built for an exec of Willard Marine, and he had it built exactly that way. I accompanied he and his wife on a Baha Ha Ha from Long Beach to La Paz (~ nms or so) in or so, and I liked the setup a lot.

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