Insulating dry stack exhaust

I wrapped the pipes with a heavy fiberglass blanket, taped it with 4" fiberglass tape and then smeared a mastic on it. My question is did I do it right? The wall next to the muffler got r-13 insulation and the a 1/4" piece of concrete board. The temperature before the wrap was about 165 degrees. The engine temp was about 165 and I put my hand on the muffler and I could leave it there. Not very hot at all.

You done good if it wont set the boat on fire and a hand touch doesn't hurt.

And is as quiet as a gas car outside.

Did you set it up to USE the heat , like running it thru a hanging locker to dry wet gear?

No but there is going to be a washer/dryer right next too it.

Custom made insulation blankets are the norm, with lace-up hooks to cinch then around the pipes and fittings. Because the blankets are removable, they facilitate inspection and repair of the exhaust system.

My only concern with your approach is whether it will disintegrate over time due to vibration. Will it all remain accessible for inspection?

While maybe the norm on yachts and some commercial boats, fiberglass lagging is still,pretty common for operators with limited budgets.

Several of the commercial boats I run still have the fiberglass taped lagging, one or two have a combo so the parts most likely needing work or inspection have the blankets for convenience.

I have never priced the big ones but the only small ones I have dealt with just wrapping an injection elbow were pretty pricey.

Swampu...hard to say if you did it right after all slathere'd up...a test run will tell you that. Remember the stuff stinks and smokes for awhile depending on what you used. The first 10 or so hours on my assistance towboat and I thought I was on fire every run.....sitting on the engine boxto drive that boat made it really interesting

With all due respect to what you said about watching budget, have you thought about making the investment in a hospital-grade muffler, perhaps even a used one can be procured?

I've lived with 6-71s, love them to pieces, but the noise becomes fatiguing if not managed properly, and your muffler passes right through your deckhouse. Could be one of the best investments you make.

However you plan to "box in" that exhaust trunk, you might want to insulate it with some mass loaded vinyl and mineral wool.

And yes, under load and up to operating temp, you should be able to put your hand on it and leave it there.

A temp gun at harbor freight is about $20

Where is your expansion joint?

Swampu...hard to say if you did it right after all slathere'd up...a test run will tell you that. Remember the stuff stinks and smokes for awhile depending on what you used. The first 10 or so hours on my assistance towboat and I thought I was on fire every run.....sitting on the engine boxto drive that boat made it really interesting [/QUOTE]

In the "old days" I did an exhaust with asbestos rope and waterglas to coat
it. It did STINK when the exhaust heated up.
Years later I did another one with insulating "rope", but I coated it with a
mixture of flour and water (paste), it smelled like fresh bread baking.
Never got to the burned smell.

Ted

Wrapping with aluminum flashing does a lot to reduce radiative heat transfer.

You need to do a test run at high power setting to make sure temps are ok. Exh gas temp probably around 800F for those motors and so you need to be sure the insulation job is good enough to keep temps moderate on nearby wood.

This needs to be done carefully. For reasons obvious, especially on the Rose!!

ulysses said:

Where is your expansion joint?

Click to expand...

The joint in the pipe runs from the manifold to the elbow going up to the muffler. I didn't put a joint in the tape. I was planning on down the road installing blankets on the lower pipes. Unless it works. I was going to box in the muffler using the concrete board on wood 2x4's and lots of wool insulation. As it sits how hot is too hot for the muffler. I'll be taking a 5 hour trip to the yard in 4 weeks so that will be a good time to test the wrap before I cover it up.

Ski in NC said:

Wrapping with aluminum flashing does a lot to reduce radiative heat transfer.

You need to do a test run at high power setting to make sure temps are ok. Exh gas temp probably around 800F for those motors and so you need to be sure the insulation job is good enough to keep temps moderate on nearby wood.

This needs to be done carefully. For reasons obvious, especially on the Rose!!

Click to expand...

Thanks, I was going to pm you and pick your brain about this but it had to get done Saturday and the cloth was my only option for now, if it doesn't work Great then I'll not close in the mufflers till I get blankets. Can I install some louvre on the pipe ends to keep water from soaking the mat? I have outer stacks that bolt to the roof and the exhaust pipe runs through it. Thanks

Ted; said:

Years later I did another one with insulating "rope", but I coated it with a mixture of flour and water (paste), it smelled like fresh bread baking.

Click to expand...

First thing came to mind...
Yep, poor ol' Ted swall'd his exhaust pipe.