I have commented on this subject before so I hope you all don't mind my
re-post on this subject. My impression is that mufflers need to be replaced
proactively every 10 years along with mixing elbows. This is cheap
insurance because you will float your floorboards and get soot inside your
boat. It is ugly. Just pay the $375 for a new muffler and save yourself the
aggravation.
Here are the details of my mixing elbow / aqua lift muffler replacement
project.
I have about 500 hours on a 2004 C320 with a Yanmar 3GM30F-YEU. The
mechanic recommended I change the mixing elbow in the next 12 months. The
U Mixing Elbow inside was corroded at the point where the raw cool raw
water mixes with exhaust. The riser appeared to be in good shape but the
two parts looked to be bonded together and my mechanic told me to replace
the entire assembly Elbow, riser and join. I read several owners accounts
of failed mixing elbows and mufflers / muffler repairs. The lead time to
get a muffler from Catalina was estimated to be 2 months. The general
consensus was to replace the muffler after about 10 years. Mufflers seem to
fail mostly near the screw holes in the corners. Some owners think this is
due to vibration from the engine exhaust hose. I used Jeff Hares rule and
decided to replace the muffler on my schedule instead of the boats schedule
especially because of the 2 month lead time for the muffler. The cost of
the muffler from Catalina was $374.
I contacted Ken Roy at Catalina and gave him my hull number and some
pictures and dimensions of my existing muffler (it is for sale now). Ken
asked for some more dimensions. Ken sent me back a picture of the muffler
he proposed to make for me and requested payment. It took about 2 months
total to get the muffler.
I ordered the gasket, mixing elbow, SS joint and riser exhaust from
Bayshore Marine(see below). Next, I considered the muffler vibration issue.
Some owners felt that a hump hose would isolate the vibration from the
engine to the muffler. The existing wet exhaust hose connecting mixing
elbow to muffler input was a 22 inch 2 in. id. I decided replace with 2
hose segments of more flexible trident corrugated exhaust hose joined
together with an exhaust hump hose I purchased from Catalina Direct.
Here are the details. The procedure took about 3.5 hours including driving
home once.
1. I turned off the raw water thru hull, disconnected the 3/8 hose
connection at the elbow, the 4 riser exhaust bolts came off with no
problem. Then I disconnected the elbow from the 2 in. exhaust hose. I used
a radiator hose pick to remove the hoses. They came right off with no
problem. Don’t sweat removing the hoses.
2. I took the old elbow assembly home where I used it for reference
to create the new assembly using a vise. I don’t believe you can create the
new assembly without the help of a vise and 2 large adjustable 15 in
wrenches. Don’t try to make the new assembly on your boat! You will need to
twist the 3/8 in input 180 degrees then you will need to create the exact
same angle as the old elbow by threading the joint into the elbow and
exhaust riser. I used high temperature anti seize on the joint threads
before assembly.
3. I used a gasket scraper to easily remove the old gasket. Then I
applied some high temp gasket seating material to both sides of the new
gasket and bolted the elbow assembly to the motor.
4. I removed the 4 stainless screws securing the muffler to the boat
and I removed the output exhaust hose from the old muffler using the
radiator hose pick. The hoses come off the muffler without any problem.
The muffler comes out of the boat without any problem.
5. I put the new muffler in place and connected the output exhaust
hose without any issues. I found the screw holes on the new muffler did not
match the screw holes on the muffler. I could get the 2 screw holes
forward to line up but then the aft screw holes with not align with the
existing holes. Access to the forward inboard screw is somewhat limited so
you will want to match the forward inboard screw with the existing hole
then use a drill motor to self tap new holes with the muffler in place. The
existing self tapping screws were in good shape and I did not need to drill
pilot holes, I just drove the screws into the glass with the muffler in
place after I screwed down the forward screws. Apply a good amount of
silicon grease to the muffler drain.
6. I used a sawzall to cut an 8 in and 13 in segment of corrugated
exhaust hose then I joined them with a hump hose using double hose clamps
on each side of the hump hose. Then I connected the hose to the mixing
elbow and the input side of the muffler.
7. I turned on the thru hull and ran the engine. White fiberglass
chips from the new muffler were spitting out the exhaust for a while. No
leaks. The hump hose appeared to do the job limiting vibration. I left the
rear engine cover off and took the boat out in open water and ran the motor
up 3000 RPM. I went below and to my surprise I saw smoke coming from the
exhaust riser side of the stainless steel joint nut! No water. It appeared
that the joint was oozing and burning anti-seize. After about 10 minutes
this smoking stopped. I’m assuming this is normal but it spooked me. I’m
going to put a co2 monitor in the aft cabin to make sure I don’t have gas
leaks.
Parts:
bayshore marine:
128370-13201 gasket $4.92
124070-13520 U mixing elbow $169.33
128370-13610 riser exhaust $130.39
104214-13580 joint $28.79
Note:
27233-250000 plug comes with 124070-13610
124070-13300 elbow 3/8 comes with 124070-13610
Parts from Catalina Yachts (
K...@catalinayachts.com)
1 Muffler $374 plus Shipping
Parts from Catalina direct:
High Temp Anti-Seize Compound (#Z2858): 1
Item Total: $15.95
Exhaust Hump Hose 1-5/8"I.D X 6" (#Z2152): 1
Item Total: $31.49
Tools Harbor Freight
8" Radiator Hose Pick $3.99
Carbon/Gasket Scraper $2.99
High Temp Gasket seating compound
MMI Marine
TRI252-2004
TRIDENT CORRUGATED FLEX SAE J2006 MARINE WET EXHAUST HOSE (HARD WALL WITH
WIRE) - 2 Feet $15.00
BUA70HSS36C
BUCK HOSE CLAMPS S/S FROM 1 13/16" TO 2 3/4" 4 $8.00
Danny Jensen
A BOA VIDA
Hull 972