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Streak 06-09-2012 01:52 PM

mcx exhaust manifold leaking
I have a 2006 MCX (197 prostar) in which the (black) exhaust manifolds have developed leaks in the centre of the (frost) plug/covers located at different positions on the manifold itself. It seems others have had the same problem. Not sure if they are frost plugs or covers for the initial manufacturing, but the seem to be a welded portion 1" in diameter that have developed a hole in the middle and now spurt water when engine is running (pictures of others :

can you give any advice to repair (I've heard of JB weld), or replacement parts if available (indmar seemed to think that I could purchase replacement "caps" from and "press" them into place.

If the manifolds are corroding in these places, does it mean they are corroded inside and will that affect engine operation - can this put water into the block??!

Craig Brown
[email protected]

CantRepeat 06-09-2012 01:58 PM

I'm not sure how you linked the photos but its going to a 404 error.

CantRepeat 06-09-2012 01:59 PM

They are casting plugs. I know some people have pulled the manifolds off and had new plugs TIG welded in.

snork 06-09-2012 02:17 PM

Had the same thing happen to my 04 mcx
had Indmar replace under warranty

[email protected] 06-09-2012 02:36 PM

Casting plugs are your first choice. JB Weld marine is your second. Clean the area real good then
apply the JB Weld...Clean and paint gloss black. Casting plugs are avail from any INDMAR and or MC Dealer

[email protected]

Streak 06-09-2012 03:17 PM

After some in-depth research on this site (thanks to macattack for his input), I found that the exhaust manifolds have casting manufacturing holes that are covered by aluminum caps (welded). These actually act as anodes to the exhaust manifold and corrode over time - even in fresh water.

Tempo fix seems to be JD weld, proper fix: aluminum casting caps from Indmar TIG welded to the manifold after proper removal of the corroded parts.

Once again, I'm impressed with the quality of info and people on this site and will keep using it to help others if I can.

Thanks all

hurricunning 08-15-2012 03:27 PM

1 Attachment(s)
Have the very same problem on 04 MCX in a prostar 209 I am negotiating the purchase of right now! New manifolds look to be $727 each on Anybody have an idea of the cost of a full set of plugs and rewelding ballpark?

Cheers, Chris

sp00ky 05-18-2013 02:10 PM


Originally Posted by CantRepeat (Post 847578)
They are casting plugs. I know some people have pulled the manifolds off and had new plugs TIG welded in.

Ok my 94 205 is leaking from a similar place except there are on the sides. The jb water weld route is what Im about to do.

But replacing these caps requires removal of exhaust manifold/risers? Being that is a 94 and I'm not sure when these have been inspected.

Do I run the risk of damaging anything by removing? Has anyone had this done.

snork 05-18-2013 02:35 PM

get yourself some gaskets when re-installing the headers or risers

Engine Nut 05-18-2013 03:25 PM

You can prevent electrolysis from attacking the plugs in the manifolds by separating the quick drain hose that runs between the manifolds and draining them any time the boat is going to sit unused for more than a couple of days. No electrolyte ... no electrolysis.

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