Replacing your dry stack muffler
By Scott Flanders on M/V Egret
OK, here's the deal if you own a smaller N or similar dry stack boat and your muffler needs replacing. We replaced Egret's muffler after 8 1/2 years of ownership. We should have replaced the muffler perhaps 2 or more years earlier after looking at it when it came out. I have a theory how the muffler came to be a rust bucket. Over the years we have taken considerable salt spray over the boat deck onto the exhaust pipe. After a long run in heavy spray the stack turns white from salt. When it rains the salt melts and in time it runs down the stack thru the poor seal on the funnel shaped rain guard over the fiberglass stack. When we get a chance we will clean the stack to bright metal then will wrap the joint with a tape we bought locally that will withstand 500 degrees F. While running I used an infrared heat gun and the stack temp at the seal was less than 275 degrees F. Hopefully this will keep salt from running down on top of the muffler and saturating the heat blanket.
Replacing the muffler is a job you can do yourself if you have a helper. You will need a couple tools you may not have but it is no big expense. We used metric sizes even though the muffler is U.S. built. The tools we used are pictured below.
There are three tools that are key. The most important, we had to modify a 26mm open end - closed end wrench (spanner). We cut off the open end leaving the closed end. The overall length of this cut down wrench is 8 3/4" (220mm) from outside the ring at the ring end to the cut off end. This length is key. If its longer it won't get into some of the places it needs to go. This wrench fits the nuts on the flange bolts. The second tool is a 24 - 28mm open end wrench*. You use the 28mm end to hold the head of the bolt for the flange nut. The third tool is a short handle 3lb hammer. You use this to beat the **** out of the cut down wrench to break the nut free. A long pipe slid over the cut down wrench will not break the nuts loose (we tried). Additionally you will need a pair of channel lock pliers, 2 - 14mm/9/16" wrenches, a 1/2" drive breaker bar, a 6" extension and a 28mm socket. Thrown into the mix is a quality Liquid Wrench type product (we used Corrosion Block that works on everything) and a secret product called Anti Bond (available from lewismarine.com). Anti Bond will save you tons of time as well as the gel coat on your stack removing the stainless trim ring (held in place by 4 - 3/8" bolts and adhesive bedding. Anti Bond turns the bedding loose. We also bought a 50 meter (160') roll of 2" shiny aluminum heat resistant tape to cover everything when we were done. (Don't even think of using duct tape.) And 3 meters (9 1/2') of 2" fiberglass heat shield tape.
Egret's muffler was manufactured by Harco Manufacturing Company in the U.S. The closest muffler number is 824VRS3. This muffler is not an exact replacement but it is close. DO NOT ORDER THIS MUFFLER BY THIS NUMBER!!! This number is to get you close, that is all. Egret's muffler is 32" (810mm) tall, measured from flange outside to flange outside. The flanges are 7 1/2" in diameter with 3/4" holes on 6" centers. This is a U.S. standard flange size and your new muffler must EXACTLY meet this standard as well as the flange diameter, bolt pattern, diameter and overall length. The reason is the heat blankets are custom made to fit your particular muffler.
If your muffler is a different dimension than Egret's it is no biggie. These mufflers are made to order. The manufacturing time is one week. The cost for the U.S. made muffler bought from Harco is $375 in mild steel (what came from PAE) and stainless steel is a little over $1000 (minus taxes and freight). In Egret's case we ordered stainless steel that gives 2-3 times the life. Be sure and order 2 flange gaskets with the muffler.
We ordered Egret's muffler in Launceston, Tasmania from Northern Mufflers. They bought the muffler from Chromend Supply in Melbourne (Daniel). Chromend's phone number is 02 45 88 5089 (in Australia or 0612 45 885089 outside Australia) We paid a little over $1500*** AU for everything including GST (tax) silver tape, 2" fiberglass fire blanket tape, and so on. A mild steel muffler and the rest of the parts plus GST would have cost about $750.
Both mufflers, the original and Chromend's have spark arresters inside. If you order one from Chromend specify a spark arrester. It costs $150 AU more**** but we didn't want sparks and I don't think you do. And one last thing. If the muffler whistles loudly on startup it is installed upside down. Muffler flow is directional so be sure and install the muffler with the flow arrow pointing upward. Egret's muffler's weld on label was mis-marked. Soooo, we got to do it ALL again and WHY I can remember all the details.
So there you have it. Another BU+ (boat unit) gone but it is the price we pay for freedom. It's OK.
*This is also the size for your Lugger motor mounts.
**The stainless steel tail piece is welded on a slight angle. Be sure and mark its fore and aft direction so you don't make a mistake on reassembly.
***Chromend's normal stainless steel muffler is 1.6mm wall thickness. We wanted 2mm (like the tail piece) and negotiated to get 2mm at the same price.
****This is included in the figures we quoted.