MCX engine - exhaust manifold leaks?

My 2007 MCX has 650 hours....no leaks.

Thanks. I would have thought this would have been flagged more if this was a common problem. Hoping others can chime in.

my 2008 MCX no leaks (afraid to type that since my 95 350 has some) .... not a common problem in my book.

My 05 MCX with 800-ish hours has none.

Yes, this has been discussed lots here. They are called Welch plugs and Indmar carries them. They are just aluminm plugs and can be tig welded in. You can use a grinder and scrape off the paint and expose the aluminum and try to scarify it a bit. A high temperature epoxy or high temp JB Weld will do it. It will leak again if you dont get a good bond, but that is acheived by roughening up the aluminum to create a "profile" the epoxy can bond to... Think " tiny peaks and valleys" so the epoxy has something to hold on to.

If you really want to fix it without welding it, look at Belzona materials, but read the instructions.

I have an MCX and two of them started leaking. I applied a Sika high temp epoxy in the spring and then spray painted with gloss black. I will not be welding the welch plugs back in as I put 75 hours on my hoat this season and they didnt start leaking agsin.

@37tr3n5k - thanks, if this something that a MC shop would be able to fix properly as it might be a know issue? While I wish I was able to do this work the fact it that I cannot. Is this just a design flaw or QC issue?

If you are convinced you'd like a welded fix, I would not take it to MC. They will just want you to buy the manidolds at 800 a piece. If you convinced them to weld it, I cant imagine what they'd charge and they would likely outsource it anyways. I'd take the manifolds to a welding shop that can perfrom tig welding on cast aluminum. The Indmar welch plugs are a ripoff. You can buy them elsewhere for a fraction of the cost. Depending on where your leaks are, you will likely have to remove your manifolds and disconnect the muffler, etc. As I mentioned above, a proper epoxy fix is more than suitable as you see only low pressures and relatively low temps. The only issue would be adhesion and this is obtained via proper profiling of the substrate (manfold surface).

2004 MCX, 600 Hrs, No Leaks!

Another thread for reference. Search "welch" and more threads will show up. The manifolds are ETX.

I bought my 04X30 1.5 years ago with an MCX engine. It had 600 hours on the boat and the manifolds were leaking. From my research on here and talking to other members that have the same issue, the areas are actually casting plugs. The metal used to seal the areas are designed to fail first. The problem is that both sides of the manifolds have plugs. If you have some leaking eventually the others most likely will. You will not be able to easily access the ones next to the engine for repair. I brought both of my manifolds and some plugs to a local machine shop and they welded both manifolds for $150. I got a new gasket from SkiDim and changed my plugs and wires while I was at it. I used a gasket to avoid using RTp and making a mess. I’ve put approx 150 hours on them now with no issue.

If you are going to fix only the ones that are leaking and not pull the manifolds, I would strongly recommend carrying a JB weld set on the boat in the event that you have a bad leak and need a temporary fix to make it back to the dock. I carry one on mine.

As was mentioned earlier, new manifolds are $800 apiece. The ones on there are heavy duty and re-welding them has worked for me and save me quite a bit of money. The dealer is going to only do replacement.

Also, one last thing. The manifold drain plugs usually break when you take the manifolds off even if you’re careful(they are plastic). Consider going ahead and ordering a pair now. They are inexpensive.

I had a few leaking this spring (MCX, 825 hours)and a few that looked like they were about to leak. I opted to pull the manifolds, and have a welding shop replace all of them on both. I paid $100 for the plugs and about $400 for the labor. Hoping that all of them being fresh will last another 800 hours!

FWIW.. Ive always told myself instead of replacing the Indmar Manifolds, I would probably go with one of these from Eddie Marine if I was looking at replacement for any reason.

@37tr3n5k Do you think that would be a permeant fix? Better performance?

Could go all out with a set of Ilmor stainless performance headers like on Freddy's ThrowDown 7.4L ProStar.