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  #1   IP: 64.222.59.173
Old 11-25-2005, 09:56 PM
jsedivy jsedivy is offline
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New exhaust system

Dear Don,

I just purchased a rebuild engine from Moyer Marine, and it's about to be installed in my 1972 Pearson 30. Upon further reflection, this may be a good time to rebuild the exhaust system, although the current one seems to be operating fine. It looks like the original installation, which makes it over 30 years old. The manifold is connected to a double-wall jacketed exhaust pipe, which in turn is connected to a vertical copper riser, then to a rubber exhaust hose. I've read that the inner wall of the exhaust pipe can develop cracks, which in turn can allow raw water to back up into the engine. This sure would be a dreadful thing to do to a newly rebult engine!

Any recommendations you can give me would be much appreciated. I was going to put together the hot section from brass, starting with your (OVCM_04_127) exhaust flange, then your (CSOT_01.2_334) T-type cooling water exhaust entry fitting, configured as shown in the catalog, although I will have to use a 45° elbow on the tail pipe to take the exhaust to the starbord side, where the current riser is located. Not much room.

Then a new lifter, probably stainless steel - any recommendations? The connection between the exhaust pipe and lifter will probably have to be a short section of rubber hose.

Are you familiar with the original installations on the Pearson 30's? Any recommendations?

Would it be possible by any chance to get somewhere a new double-wall jacketed exhaust pipe, i.e., just like the original installation?

Right now the raw water exits at the rear or the double-wall jacketed exhaust pipe and is connected via 1/2" rubber hose to the top of the riser. I'm guessing the raw water is injected into the exhaust proper on the downslope after the riser - thus the riser itself is dry?

Or should I just forget about the original system and replace it with a completely new one put together from modern components?

Best regards

John
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  #2   IP: 38.118.52.41
Old 11-26-2005, 08:55 AM
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John,

I'm not completely sure that I understand your system. On first reading, I thought you had a typical Pearson double-walled system more commonly used on the Triton and Vanguard. However, these systems did not have a riser like you're describing, hence my confusion. Perhaps some other Pearson 30 owners can clarify things.

In the meantime, my recollection of the double-walled systems of the Tritons and Vanguards, as well as the copper water lift muffler systems of the early Pearson 30 fleet, is that they were extremely well made, and my guess is that you could pressure test yours and keep it in service. Here is a technical note we prepared on the double-walled system some time ago that may help:

"Double-walled exhaust systems are constructed by installing a pipe within a pipe, so that the engine exhaust passes through the inner pipe and engine cooling water is routed to the back of the boat through the annular space between the inner and outer pipe. The cooling water is routed through a short tube from the back of the exhaust manifold to the front of the annular space of the double-walled assembly, and another tube routes the water from the aft end of the annular space back into the exhaust pipe just before it leaves through the transom.

Double-walled exhaust systems were used primarily on Pearson Triton and Vanguard boats in the mid to late sixties. Being constructed of copper and rather difficult to manufacture, double-walled systems were quite expensive, and boat builders abandoned them during the decade of the seventies in favor of "wet" exhaust systems using water-lift mufflers.

A principal advantage of the double-walled systems is that engine cooling water had no real opportunity of backing up into the exhaust manifold unless, of course, the inner pipe failed.

Double-walled exhaust systems can still be a viable approach, as long as they are pressure checked each year. To pressure check a double-walled system, simply cap off either the water inlet or outlet and pressurize the opposite fitting. A bicycle pump with a built in gauge works well. The annular space should hold 15 to 20 psi for an hour or so.

Don
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  #3   IP: 128.148.123.5
Old 11-26-2005, 09:10 AM
jsedivy jsedivy is offline
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Don,

thanks for the quick reply. I think the confusion is on my part, since I was not quite sure what to call the verical copper piece - what you refer to as the "copper water lift muffler systems of the early Pearson 30 fleet". I'll take a picture and attach it later today. Sorry for the fuss, but I'd really hate to ruin the engine you just spent good time rebuilding. I'll do a pressure test as you suggest. You think doing this each spring is safe enough? Is there anything that can fail in the "copper water lift muffler" - I'm still not sure how that thing works inside.

Best - John
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  #4   IP: 38.118.52.41
Old 11-27-2005, 07:51 AM
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John,

The size and shape of water lift mufflers varies considerably, but the principle seems to remain somewhat the same. Exhaust and cooling water from the engine enter at or near the top of an enclosed container. An outlet is provided which usually extends from the top of the container, but the inside of which extends down inside the container, very close to the bottom (within an inch or so).

In operation, the water level builds up inside the container until the exhaust pressure builds up sufficiently to lift the water out of the outlet pipe (hence the name) and out through the transom via reinforced rubber exhaust hose. There is always a level of water maintained inside the container to a level just above the bottom of the outlet pipe which muffles the sound of the engine which accounts for the second part of the name.

As to how water lift mufflers fail, they could of course develop a leak. Or, the outlet pipe can eventually corrode/erode away which would leave (in worst cases) the muffler container to fill with water and greatly raise exhaust back pressure. And they can fill with sediment and crud, which would again create excess exhaust back pressure.

My understanding is that the Pearson 30 copper water lift muffler assemblies are very resistant to corrosion and have an excellent survival rate, in spite of their age.

Don
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  #5   IP: 128.148.123.7
Old 11-27-2005, 10:04 AM
jsedivy jsedivy is offline
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Don,

here are the pictures I promised.

Picture 1 shows the double-wall exhaust pipe. It's connected to the muffler in the lower left. Raw water enters on the right (close to the engine) and exits on the left, just before the muffler.

Picture 2 shows a closeup of the connection between the exhaust pipe and muffler, taken from inside the engine compartment.

Picture 3 shows the same, taken from behind (looking towards the bow). The orange rubber hose takes the water from the rear of the exhaust pipe and to the very top of the muffler.

Picture 4 shows the same view from further back, so that you can see the 2" rubber exhaust hose exiting the muffler.

Picture 5 shows the same view, but higher up, so that you can see the top of the muffler and the hose that injects the raw water.

What was confusing me is that in this setup the exhaust gas enters the muffler on the bottom, but the water enters at the top.

On your recommendation I will keep all components, but I think I will take them out of the boat, give them a good cleaning, and re-paint them.

Thanks for your help,

John
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  #6   IP: 38.118.52.41
Old 11-27-2005, 07:30 PM
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John,

Thanks for the photos. I was never aware of the double-walled connection between the manifold and the inlet to the muffler. Not that it matters, but yours is a rather early Pearson 30. I wonder if this was perhaps an earlier design that was discontinued on later models.

I still think you'll be OK if you clean everything up and pressure check the double-walled section and the muffler itself for leaks.

Don
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Old 08-01-2011, 01:19 PM
burnell burnell is offline
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Wrapping my new exhaust

My new exhaust system is galvanized 2" diameter pipe treaded into t90 degree '"Ls".

I have wrapped it with 2" by1/8 inch fiberglass from West Marine (wish I'd noticed your new kit first).

The "L's" are hard to get a nice smooth wrap on. I'd like to wrap the wrap with that modern duct tape so I can splice small pieces of fiberglass together around the "L's" and still have a smooth, durable job.

However, the highest temperature spec I can find is Nashua''s Premium Foil Tape rated for 325 degrees F.
Is foil tape acceptable?
What do you suggest?
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  #8   IP: 64.134.224.145
Old 08-01-2011, 01:36 PM
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roadnsky roadnsky is offline
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Quote:
Originally Posted by burnell View Post
However, the highest temperature spec I can find is Nashua''s Premium Foil Tape rated for 325 degrees F.
Is foil tape acceptable?
What do you suggest?
Use the wrap that MMI sells on this site in the CATALOG section.
It works great and supports a good cause too!

Just do a twist at the "L" sections.
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Last edited by roadnsky; 08-01-2011 at 01:38 PM.
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  #9   IP: 74.108.39.167
Old 08-01-2011, 02:08 PM
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Another data point on P30 mufflers: Here's a photo from my 1976 P30, I don't know if it is original, but it looks it.




A question for John:

How did you get the motor out of your P30? I'm thinking about a motor swap for my boat, but I'm not sure how to get it out of there. I guess I'll have to disassemble part of the galley?
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  #10   IP: 64.12.116.80
Old 08-01-2011, 03:38 PM
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gary gerber gary gerber is offline
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I can tell you from my experience concerning the double walled exhaust pipe, on my 1970 Morgan the original pipe ran UPHILL toward the stern so when the inner pipe failed water ran downhill into the combustion chambers. Fortunately i was able to address the failure promptly and install a new system using Moyer parts and Vetus parts. If your boat is 30+ years old and there is a risk of the exhaust water getting back into the engine I think now is the time to change the configuration. Good luck.
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  #11   IP: 173.116.136.120
Old 08-01-2011, 06:43 PM
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Quote:
Originally Posted by Loki9 View Post
A question for John:

How did you get the motor out of your P30? I'm thinking about a motor swap for my boat, but I'm not sure how to get it out of there. I guess I'll have to disassemble part of the galley?
Loki-
Note that John's post of this thread was in 2005...
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  #12   IP: 74.108.39.167
Old 08-01-2011, 07:50 PM
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Quote:
Originally Posted by roadnsky View Post
Loki-
Note that John's post of this thread was in 2005...
Wow, didn't see that. Crazy bump.
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