Exhaust Manifold

I (Jon) finished these jobs variously on Mar. 9th.

Forever ago as we were sailing to Tonga, the exhaust manifold sheared two of the four bolt studs that hold the manifold onto the engine. Part 1 of the story is here. Part 2 is here. Much frustration was derived from making a temporary fix. This involved drilling out the stud that had sheered, then drilling out the drill bit that broke while trying to drill out the sheered stud. We then re-tapped the hole with larger threads. Enlarged the hole in the exhaust manifold which bolt passes through to help with alignment. And finally, Matt made up a heavy duty bracket, that while he calls it janky, is probably what kept it from breaking again.

I now set about to making a more permanent fix. We had helio-coils flown in to Fiji, but never got around to installing them. So that became my job. I drained the coolant and pulled the exhaust manifold off. Doing this on my own was much harder than when Matt and I were both able to fit in the engine room and get four ands on it. But it happened.

Another bolt had sheered at some point either sometime in the last few months or now when I was talking off the manifold, so I had to drill that out, though it came out much easier than the ones we drilled out in Tonga.

Then I tapped the holes with the helio-coil tap and inserted the helio-coils. This was easier than I expected. Than I inserted the new studs we ordered. Our temporary fix was using bolts to hold it on, but the factory spec’ed studs should be stronger. There are long studs and short studs you can order. We ordered both because Matt wasn’t sure which were ours. it’s ends up our manifold uses the long studs. There is one old stud still in the engine block, the 2nd one from front of the boat. It was completely seized inside the engine block, which isn’t a terrible thing.

After this, the exhaust manifold, of course, wouldn’t fit back on. I hadn’t perfectly centered the studs when tapping with the helio-coil kit. (and you unfortunately can’t temporarily mount the manifold and drill and tap through the old holes to make sure  you have perfect alignment. The way the manifold is constructed precludes allowing a drill to get close enough) So I had to enlarge the holes in the exhaust manifold that the studs pass through.

We also had bought new gaskets for in between the manifold and the engine block, so those were applied. And the gaskets were also slathered with purple Permatex.

I think that’s about it. Despite that it should be perfectly back to new, I put Matt’s bracket back on, as it seems like there’s no reason why not.