InvertaFlow Muffler Repair DIY

Let's hope this goes well, but I am just about ready to attempt a big time repair of my muffler on my '92 Nautique. I did find that I could buy a new one, but the price was $600+. So it is worth it to try my hand at this. So this thread is ongoing. This fall a backfire during winterization blew out my muffler. The PO had repaired one side in the past.







So now I have done my best to clean up the ruff edges. One of the endcaps is usable, the other is not. The triangle shape in the middle is part of the un-usable cap. I am buying a 12 x 12 sheet of fiberglass resign 3/16" thick. Not the cloth, this is a fireproof "board" from : eplastics.com

Here is the clean up:
After scrubbing inside and out with Marine Clean, I used a 4" disk on my angle grinder and cut the loose material off, then ground the edges flat on both ends of the tube and the 1 cap.



The disk on the right is the end cap I am going to use, the disk on the left is the remainder of the PO's repair it is trash. It looks like the disk lays on the edge of the angled cut tube and then the glass mat and resign are applied...

More to come once I get the supplies. Chime in with thoughts.

I'm doing it right now, a little slow getting too it, but hope to have time to finish it up this weekend.

If you don't have any supplies, Soller Composites sells fiberglass sleeves which look pretty handy for round things, but I haven't used them yet so I can't say for sure. Both of my intake tubes were crushed, one was repaired by the PO, I did the other one myself. I got some new tubes and cut the old ones out, put the new ones in last weekend and faired them in with Marine Tex.   Next step is a couple of layers of tape, a 3.5 in sleeve over the top of that and a final 9in sleeve over the whole invertaflow. Hopefully it comes out looking better than new. After sanding down most of the original build looks like they were more concerned with speed of assymbly than they were with the looks of the finished product. Very simple build, looks like they used a similar fairing compound with a 2 or 3 layers of woven cloth then some mat over the top and a coat of paint to dress it up a bit.

Ok, back at it.   Resin plank is on it's way, I bought 3M resin and did some additional cleaning and ruffing up. I have now fiberglassed one of the inlet ports. You have to repair from the inside, cause the 4" flex hose needs to fit on the outside. So I read a tip...Use a balloon. So I wiped the resin inside, added fiber mat, then more resin and additional fiber mat on the weak spot. This inlet is the better of the two.



The resin and mat I used. I got it at Home Depot. 3M has another resin they say is for cars and boats (402). This one is for home interior and exterior projects (20122). I searched and searched to find a difference other than price. could not find one.


I have the muffler sitting on a table, on jack stands. I plan on rotating it until the hardner sets. might make for a even flow of resin, cause I did use JUST resin on the outside of the pipe (not in the picture)

Bad hole inlet with the balloon out. Resin has not completely hardened, but the balloon did not want to stick. I popped it after 2 hours.



balloon left a nice smooth finish. Tomorrow I'll clean up the edges. Hole is plugged! You can kinda see the hole thru the resin, but it is solid.

So far so good.

I did not think about pressure. looking at the design of the baffle, I did assume that the gases would have to go up, then down and out, but it did not register that the pressure would push the water. I figured if it got full of water it would flow up and out too. Cause that little hole was not going to handle all the H2O.

Good to know, cause I used the resin on the seam, ended up glassing over the hole, then re-drilled it.

I'll be attaching one end cap today. Waiting on the new resin plank to arrive...fingers crossed for today's mail. EDIT: they got it to fedex yesterday.... San Diego to Nashville will be next week, oh well.

IMHO I would grind all the black off down the sides where the new glass will attach that cap,you need a good bond there. I think using a dremel with a sanding drum would make quick work of it. Keep up the good work

While I did not completely remove the BLACK, I did ruff it up quite a bit with some heavy grit sandpaper. The picture was taken prior to ruffing up.

Thanks,

Clark

yes, paint it. repair looks great.

This one is ready for the classic DIY folder. It took a while, but it saved me $600. Engine is running again and I am ready for the lake.

1st picture here is the engine without the muffler. Notice the aluminum stands on either side and teh shift lever in the middle. Hard to see, but they are there.


Couple things to show on the install. I had some foam pad, see the BLUE? I cut some pieces and wedged them between the muffler and the stand.

I ended up having to remove the stands to get the muffler and pipes re-assembled.


Another thing to do is move the shift selector to forward. Again, it was touching (blocking really) the muffler during install.

This is a shot after mounting, you can see that it is clear and will shift.


and the last picture DONE. Had to get new 3" marine exhaust, or HARD HOSE the guy called it. They make it super tough to install this. I lubed up the inside of the hose with some dish washing soap so they would slide on and allow for some re-positioning.

Looks great! Anyone in the future should try heat on the hose,on the Mustang I have used my heat gun, seems to help.

HELP

How do u post a picture on here ????

scot skier wrote: Thanks I was trying to find out (I’m in Scotland) if the top lid on the invertaflow is rounded for a reason? I have now repaired with a flat piece of grip and it appears to be working however I’m worried in case I’m causing any damage

It has been too long since i looked inside. If i follow your question, i believe you are fine. You just have hot water and exhaust gases in there. Nothing comes out of that odd shaped protrusion. You could be restricting flow and losing HP. Just a guess.

Thank you for reply, yes the only info I can find does not explain the function of the rounded cap, it doesn’t appear to do anything as there’s no moving parts at all and it maybe just allows the water a smoother flow path, I have searched everywhere for info but came up against a blank so anyone out there knows anything ???