Exhaust System

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October 2006 (after a year) --

You know, when I started this page a year ago, I had no idea that the exhaust system
was going to turn into such a time and money pit. I knew it was going to be tricky,
but this turned into the most difficult part of the entire repower.
For your amusement, I present the following.



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Back at the muffler, I added a 45 degree turn
so the exhaust hose will fit on easily
without any sharp bends.

It sat like this for a month while we set the new engine into place and did all the alignment stuff (and the associated rebuilds to actually make
the alignment stuff work. Sigh.)

Gee, I was so proud of all this work.

Oh well.

October 2005 --


I was wondering why my muffler looked so new.

It was replaced in 1992.

I've also wondered why it looked like someone cut a hunk out of the quarterberth lid
and then put it back.

It was to replace the muffler.

He or she didn't do a very good job of
putting the bulkhead back together.
I'm going to move the muffler anyway,
so this will get fixed up while I'm
redoing the engine room.

The muffler hose was clamped down
*way* too tight. Note the crack in the hose
right next to the clamp.
This is a problem waiting to happen.

I've always hated the way the exhaust from the engine to the muffler was positioned.
(See Preparing to Pull the Engine.)
I didn't like the way the hose swung all the way across the compartment and blocked access to the area, and rested on the transmission.

Also, a muffler should be 14 inches below the mixer elbow, and close to the centerline.
That's to keep water from running back into the exhaust manifold when you're heeled over.

Among the owners I've polled, no LF38 has ever had a problem. However, I'm going to move the muffler anyway, as it will free up a nice storage spot, and let me route the exhaust along the left side of the engine.

The wet exhaust hose from the muffler to the transom was worn out. After 25 years,
that's to be expected.

The hose has an inner hose, then wire, then an outer sheath. Over the years, the adhesive layer has started to fail, allowing the layers to separate.
You can see the wire looping around
the hose.


Plan "A"

This little shelf will bolt onto the bulkhead
in front of the fuel tank.

It's made of prefab FRP from McMaster Carr,
with a 3" by 2" angle piece
epoxied onto a 12" by 10" piece
of premium vinylester.

The top and bottom of the joint
is reinforced with two layers of
Knytex tape from Tap Plastics.


Once the new engine's back in, I'll need to turn the exhaust around to head back to the end of the boat.
This elbow was made by taking two 90's and cutting them down , then tacking them together
with five minute epoxy.

Here's the platform with the muffler installed.

Just waiting for the engine.

Ideally, the muffler is low and on the centerline, with the muffler intake 14 inches lower than the point where the raw water enters the mixer elbow.


Here's a picture of my homemade siphon break. Okay, I need to put better brackets on there,
but that's all I had at the time.

When the engine is running, raw water shoots through the ball valve at the top and completely bypasses the exhaust system. I can use the valve to adjust the amount of water that escapes.

This reduces the amount of water
that the exhaust system has to push up hill,
which reduces back pressure on the engine

Over time, water will work up through the layers, rusting out the wire. Eventually the hose will either collapse internally, blocking the exhaust, or the wire will break and cut through the hose,
allowing exhaust (and water) into the boat. The hose will be replaced.

Well, it's not a boat project if it actually works the first time.

The huge challenge was routing the exhaust correctly.
The new engine is much lower than the old Perkins 4-108, and the mixer elbow is a good five inches lower. It's a good thing I moved the muffler, because its old location would have been higher than the exhaust manifold. That would be a disaster because water would then flow back into the engine
when the engine is turned off.

But even in the new location the muffler is too high.
By the time the exhaust does a 180 turn out of the V-Drive,
the hose would be running uphill to the muffler.
That can't be allowed.

One absolutely must have a downhill run
from the mixer elbow to the muffler.

The whole thing was well wrapped with Kyntex Tape
(X Cloth with Mat) from Tap Plastics.

It's painted with some high temperature engine paint from a local auto parts store.

(Actually, I did this twice, because I didn't get the angles right the first time.)


The Death of Plan "A"

The Exhaust hose needs to loop up above the waterline, to prevent water from coming back into the boat and down to the engine.

Fortunately, I had already added small Beckson ports in the sides of the cockpit for access to wiring and deck fittings, so it was really easy to reach down and grab the hose, and pull it up into place.

A little scrap of old battery wire worked well
to hold it in place. I crimped two 3/8" lugs on either end and reinforced it with heat shrink, then used one of the bolts for this big padeye that's attached to the cockpit coaming.

That holds the hose right at deck level, and I don't think I have to worry about chafing the hose.

Plan "B"

There are two options at this point:
1) Raise the Riser
2) Lower the Muffler.

I talked to four mechanics, and two Universal/Westerbeke distributors, looking for a part that would let me raise the riser.
Because the engine has a proprietary flange on both
the manifold and the riser, it would need to be a proprietary part.
However, none of the experts had any ideas,
though they all asked for a blank check to solve the problem.

I decided to lower the muffler. After measuring, I found that I could lower the Naqualift muffler a couple of inches,
but it didn't seem like it would be enough.

So I searched for mufflers that had input fittings as low as possible. This muffler is made by Vetus. I'm not a big fan of Vetus mufflers, because I like FRP mufflers instead of non-reinforced plastic. However, this one has the fitting down at the bottom of the muffler.

It's not sitting on a shelf,
but is suspended against a bulkhead.
The bottom is about 1/2" off the hull.

Vetus supplies plastic tie straps and little plastic brackets, but I elected to do something stronger. I think I'll add another big hose clamp up at the top, just for fun.

This muffler is much bigger, and can hold over two gallons of water.

Here's a picture of the interior construction
(used without permission) that shows why I feel it will work.

This is different from most waterlift mufflers, in that it has two chambers. When I turn the engine off, water will run back down the 10 foot long final section of exhaust hose, but will stay, for the most part, in the top chamber. The entire top chamber must fill up before water will fall down into the bottom chamber. That should help minimize the amount of water that can flow backwards towards the engine.

The first snag in this plan was the fittings. The new muffler has two inch fittings, but my old one had 1-7/8" fittings.
I probably should just go get a new 10 foot section of 2" hose, but I've already installed the 1-78" hose and that stuff is really expensive. I don't think the difference will hurt anything, so I made an adapter by building up a little 1-7/8" fitting to be 2" on one end.

This stuff is just an experiment,
but I've always wanted to give it a try.

It's a special epoxy impregnated fabric
that cures on contact with air.

You can speed it up by soaking it in water for 30 seconds, then wrapping it around a broken pipe or fitting. It's good to 600 degrees, and cures in 20 minutes.

It would be a good thing to keep on the boat for emergency repairs.

The two support braces for the Vetus muffler
are made from square prefab RFP tubes. Fortunately, I had it sitting in the garage from another project, but they work great for this.

I also had some of these 5-16" stainless stud bolts left over. So I took off the fiberglass beam that reinforces the bulkhead in front of the new fuel tank, and glued the studs into that beam.

I measured wrong the first time, so now I have a couple of extra holes in the beam. Oh well.

Plan "C"

With the engine running,
I stopped to clean up the boat and found this little scrap of paper. It was ripped in half and crumpled, but I took a look at it before tossing it in the trash.
It had all the same basic information from the Installation Manual, about torque specs and gasket requirements. But at the bottom it mentions a part number for an adapter that takes the flanged fitting and outputs an NPT threaded fitting.

I used a hole saw to lightly score the fiberglass, and then my Handy Dremel Tool
to remove a little bit of the fiberglass.
This allows the stud to sit flush.

This is good enough so I could start the engine and start dealing with other details.
But I'm not comfortable with it,
because I need to plan for pitching down off the top of a wave, which will make water rush forward.

There's enough sag in the hose to trap about a half pint of water. I took the hose off after running the engine and saw that the bottom compartment of the muffler was filled with water up to the hose fitting.

That means that enough water could spill back into the hose to gain some significant momentum moving forward, and then splash hard against the fiberglass elbow and work up to the engine.
Frankly, it's a pretty small risk at this point,
and part of me wants to just live with it.

Then I got lazy. Rather than epoxy them in and lay glass over it, I just set them in a big glop of
Marine-Tex. This is the fast setting stuff, and I wanted to get the muffler installed today.

The Death of Plan "B"

Well, the hose now has a three degree angle downhill.

When you add in the vertical drop from the fiberglass elbow that turns the exhaust around,
I almost get my 14" drop from the top of the mixer elbow to the intake of the muffler.

Eureka! This is what I was looking for two months ago.

I can take the NPT fittings and use pipe to raise the exhaust riser. I sure wish one of the mechanics or Westerbeke/Universal distributors that I spoke with had known about this. I also sure wish I'd kept this little piece of paper with the rest of the engine documentation.

Here's what the part looks like. I got two "female" parts.

Gosh, If I had this thing in hand a few months ago I would have saved a bunch of money.



I didn't want to have any custom fabricated parts, so tried to put the hardware together with off the shelf parts of stainless steel.

But it's too heavy, and all the joints and stuff will really create turbulence for the exhaust gasses, and that creates back pressure.

Universal placed the same warning in four places:

The warning says that the mixer elbow assembly cannot weigh more than eight pounds, or it will stress the bolts holding the exhaust manifold onto the block. I thought it was too heavy,
so I pulled the mixer elbow off and put it all in a box
and took it to the grocery store.

Even counting on the box, I'm far too heavy.

Three weeks and $170 later, I have
my very own custom exhaust pipe.

It's lighter, and also smoother inside, which is probably a good thing.

After installation, I was wishing I'd made one of the legs an inch longer.
Oh well, too late now.

This is the actual mixer.

When I bought the engine, I had specifically said not to order the mixer elbow, because I knew the exhaust system was going to be tricky and
didn't know which mixer would fit.
But this one showed up anyway.
It's a good design, just heavy.

I like it because the raw water passes over the top, and keeps the entire thing cool.
The water doesn't actually mix with the exhaust until just above the hose fitting.
With the engine at running temperature,
you can leave your hand on it.
It stays about 120 F, though of course the raw water temp on the SF Bay
is always less than 60.

The remote oil filter definitely needs to be kept away from the exhaust system. I don't want any oil drips to hit the exhaust pipe.

After looking at it for a day, I just moved it up four inches.
I may need to find longer hoses for it.
The hose length limits my options right now.

The oil hoses get pretty hot, so some wiring needed to be adjusted. This is a standard Ancor wire strap, with the stock rubber replaced with hose. The rubber chafe protection that comes with the bracket isn't very sturdy, and
likes to slip off.

The raw water hose from the heat exchanger to the siphon break needed to be moved away from the new exhaust pipe, so I just took a hole saw to my nice new bulkhead.

I slipped a piece of sanitation hose over the raw water hose as it passes through the bulkhead, so that it won't chafe. it's an important hose, and it's below the waterline.

Whew. There goes another weekend.

Everything is out of the way,
and it's time to test it.

Note that I wrapped some sanitation hose around the hoses to the oil filter, as well. Nothing was touching, but I didn't like having wires in such close proximity.

Here's the full side view. In addition to picking up another couple of inches of height at the mixer elbow side, there's a nice downward slope from the mixer to the muffler. I feel much more comfortable with this.

I think the engine likes it better, too.
It seemed to run a bit easier when I fired it up, as if there was less back pressure.

Great. It looks like I can finally start finishing the removable bulkhead that will hide this entire side of the engine. It'll be nice to have my cockpit locker back!

Naturally, to make it fit I have to move a bunch of stuff.

The new remote Oil Filter bracket is in the way, as are a bunch of hoses and wires.

I really wish I hadn't
added that cockpit drain
right there above the exhaust system.

That was stupid.
I'm seriously considering filling it in and moving it to the other side.

That pipe probably should get some insulation. I need to find something that can handle the heat
but won't get saturated with crap
and become an ugly fire hazard.


Update October 2007 -

I moved the cockpit drain over to port, so that the drain and hose are away from the exhaust elbow.

I don't think it was too hot, but I didn't like them that close. If something happens to that hose, the boat will take on water.