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Old 03-30-2013, 11:08 PM   #21
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Rocks,

My 36 has no muffler that I can see. I have 3" all the way aft.
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Old 03-31-2013, 01:58 AM   #22
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[QUOTE=Brooksie;

"If the exhaust hose can be rearanged (or elbows raised) so it slopes continuously down to the transom, and the mufflers do not hold water, you are fine with 9-10" drop. If not, a waterlift muffler in the engine space, as shown in a previous post, may be the answer but waterlifts have their own criteria for installation. They must be able to hold all of the accumulated water in the system aft of them for one. [B]They also can fill with water and overflow into the engine under certain conditions."[/B]

I, unfortunately, can confirm that. In our previous boat we had a waterlift muffler, and unbeknown to us, when the boat was having some work done, the yard slipped the boat stern first on a steep travel way. The muffler elbow was higher than the head and filled two of the cylinders with raw water. we only discovered that when six weeks later the boat refused to start. In all, that resulted in a $26,000 insurance claim, and the boat being out of action for the whole summer.
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Old 03-31-2013, 02:57 AM   #23
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A while back I had a sailboat with an anti water-lock device in the exhaust line, after a long tack with the exhaust underwater it "hydraulic-ed"; water in the exhaust stopped up the exhaust system, the little Volvo broke its crankshaft on starting. Inconvenient, expensive, cheapest way out was a new engine. It`s an area fraught with danger.
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Old 03-31-2013, 07:39 AM   #24
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It`s an area fraught with danger. __________________

Maybe the advantages of keel cooled , dry stack will finally make it into the Yachty market?
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Old 03-31-2013, 11:06 AM   #25
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Quote:
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Rocks,

I had National Marine Exhaust in Marysville Washington State build one for me w SS and I'm very happy w it. $750.

I'd probably go for lift mufflers.
Second that recommendation for Scott Conahan at National Marine Exhaust. Among other accomplishments, his company was an OEM supplier for Bayliner motor yachts. They can custom design and manufacture anything you need.
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Old 03-31-2013, 05:17 PM   #26
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Waterlift ... fine if you decide you need it but those engines are pretty quiet so I' don't think you'll notice much of a noise difference.

I strongly advise against plastic waterlift mufflers in any marine application as I have seen a few melted units. I have also seen high quality 6", heavy walled exhuast hose melt in an overheat situation. Imagine how fast that plastic muffler will melt if you blow an impeller.
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Old 03-31-2013, 08:35 PM   #27
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Originally Posted by On The Rocks View Post
Looking at the exhaust on my Gulf Star 36 Trawler with twin 4-154 Perkins (60 hp). The exhaust manifold/water injection elbow is 2" diameter and about 9-10" above water line. Attached to the elbow is 4" diameter hose running along the chine of the hull aft to the mufflers and out through the transom. The mufflers are not water lift units and they are mounted about 4-6" above the lowest point of the exhaust hose. My concern is that when I disconnected the hose from the manifold the standing water level in the hose was only about 12" from the exhaust manifold. Although I haven't had a problem it seems a little close for comfort. I've been thinking of raising the height of the injection point. My questions are:

Ideas for sourcing injection elbows?

Is the 4" hose & muffler overkill for this engine? My Perkins guy says the exhaust should be 2" all the way to the transom. The 2" would be easier to route but I don't want to create a backpressure problem.

Does anyone know the size and configuration Gulf Star used?


Starboard
Attachment 16578

Port
Attachment 16579


Its hard to tell for sure from your pic but it looks like you go from 4" to 3" to me. It appears to reduce just under the shelf in the engine room?
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Old 03-31-2013, 08:48 PM   #28
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Wet exhaust here (for better or worse).

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Old 03-31-2013, 08:59 PM   #29
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Originally Posted by boatpoker View Post
Waterlift ... fine if you decide you need it but those engines are pretty quiet so I' don't think you'll notice much of a noise difference.

I strongly advise against plastic waterlift mufflers in any marine application as I have seen a few melted units. I have also seen high quality 6", heavy walled exhuast hose melt in an overheat situation. Imagine how fast that plastic muffler will melt if you blow an impeller.
You're going to have bigger problems if you blow an impeller and let the engine run that long. If the mufflers are glassed with the proper resin, they will hold up OK until the engine seizes.
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Old 03-31-2013, 11:30 PM   #30
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Rocks, I had a friend with a Gulf Star in the LA Harbor. Did you buy your boat used in LA?

I read and re read your original post and I don't understand your need to change the wet elbow.
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Old 04-01-2013, 01:28 PM   #31
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The hose barb on the injection elbow is 2.5". It has two layers of hose on it expanding to 3" which runs along the bilge through lockers in the aft cabin to FRP mufflers and then uphill (about a 3 or 4 inch rise) to the transom (I took the hose off the elbow last weekend so was able to accurately measure). The problem is that there is a low spot in the hose runs at the base of the engines that collects water. When I look down into the hose, the pooled water is only about 10 inches below the exhaust manifold, too close for comfort IMHO. I don't really have room for waterlifts unless I put them in the keel which would require lengthy hose runs. I've been trying to figure out a way to get the injection elbow higher so I can have a proper slope to the transom. I looked at making something using stainless plumbing elbows but haven't found any in 2.5". Probably will need to have something fabricated.

Dry stack and keel coolers would be great but I don't have that kind of cash 😄

I noticed someone had routed the exhaust through the side of the boat. That would make the run really short but is it really advisable?
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Old 04-01-2013, 01:30 PM   #32
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BTW I bought the boat in 2005 in San Diego. As far as I know it hasn't ever spent time in L.A.
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Old 04-01-2013, 02:11 PM   #33
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Rocks,

Here is what my 4.236 looks like on the port engine and the exhaust hose in the aft stateroom. You can see I have a slight dip as well. I need to look at the date stamp on the hose but I but it is every bit of 15 years old. The PO had her for 11 years as well. I figure for here in the bay it will stay as installed.
One other note the Surveyor did not like that the water injection on this engine was at the 3 o'clock position not the 12 o'clock like the stbd engine had.

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BTW I bought the boat in 2005 in San Diego. As far as I know it hasn't ever spent time in L.A.
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Old 04-01-2013, 02:22 PM   #34
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Now I understand. Can you use a solid pipe? I've seen that in a few boats and they seem to be quieter too. I think they were FRP. Not sure but were made for exhaust and heat.
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Old 04-01-2013, 03:01 PM   #35
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Now I understand. Can you use a solid pipe? I've seen that in a few boats and they seem to be quieter too. I think they were FRP. Not sure but were made for exhaust and heat.
My boat has new steel exhaust pipe with about ten inches of exhaust hose where it connects to stainless steel through hulls. About twenty inches of hose where it connects to the manifolds.
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Old 04-01-2013, 03:13 PM   #36
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The Coot's exhaust system, showing insulated exhaust pipe from engine to a black "can" (muffler) and then pipe to outside.

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