Invertaflow Repair

Looks good Ron, I remember this job when you first posted it a few months back. Do fiberglass work enough and you'll soak up tricks to working with it like the glass does resin.

It looks good from this end! Now that you've got some glassing experience, you can tackle a stringer job.

My first how to post - be gentle :)

Last project before getting the boat out of the garage was to repair the Fiberglass Invertaflo muffler. For those who don't remember, this is what it looked like at the end of last season:




Basically one of the 3" tubes that connects to the driver side exhaust manifold had cracked/delaminated. Reading the archives, seems like this side typically runs hotter for some reason, so no big concerns on engine overheat since no other indications on engine.

After researching and contemplating over a few cold ones, decided to just cut the tube off and rebuild to minimize out of roundness/thickness errors (more on that later). Cut tube off and sanded flange areas. Here's what that looked like:



Now for the fun part - rebuilding! In full disclosure, this was my first time working with epoxy/fiberglass (more on the later :)), so I was a bit intimidated. Found a can of spray paint that fit the ID perfectly with just a few wraps of tape to snug it up in the flange and hold the cap on. I put in cap first since that end of the can did not have a flange and would therefore be easy to pull out after the epoxy set. Wrapped it with a few wraps of wax paper to prevent making it a permanent part of the muffler, and off I went:


Used West 105/206 epoxy, 6oz cloth, and 1.5 oz mat. If I had to do it again, would just stick to the cloth since it's easier to work with, or maybe some .75 oz mat since the heavier stuff was tough to get saturated and to lay flat (more on that later :)). Anyways, used a brush and spreader to wet out the glass, then wrapped it as best I could around the paint can mandrel. After it was all dry, marked and cut the tube:


Upon inspection, realized I sucked at fiberglassing! Went way to thick, and a bunch of voids/delaminations (this is the later part):


The beauty of fiberglass is that when you screw up, you can just grind it down and start again, so that's what I did. A few minutes with the grinder and a few more with some 80 grit paper (and a fairly large dusty mess), and the piece of 3" rubber exhaust hose would fit most of the way on without too much force.


All those observant eyes out there will notice that now some of the walls were pretty thin. So what I did was mix up a pretty thick slurry of epoxy and filler, and filled in the voids as best I could and wrapped a final layer of cloth over it for reinforcement:


Also applied extra epoxy to areas of the muffler that showed some wear just for extra insurance. Then a final light sanding and spray paint with black engine enamel rated for 500F to finish it off:


Overall it was a great learning experience and now I'm not intimidated by fiberglass any more! Time will tell if the repair will hold up, but I'm pretty confident it will based on my "2 hand squeeze test" to assess strength. It kind of reminded me of my first drywall repair experiences many houses ago where you put on 5 lbs of mud, then sand off 4.9 of it. Next time will be much quicker and less sanding for sure.

Hope this helps someone out there - it's the least I can do for all I've learned here.

Thanks
Ron