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Streak
06-09-2012, 01:52 PM
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 :

http://www.mastercraft.com/teamtalk/showthread.phpt=26155&highlight=leaking+exhaust+manifold

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 inboardonline.com 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??!

Thanks
Craig Brown
craigbrown8@hotmail.com

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

Jim@BAWS
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

Jim@BAWS

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
Streak

hurricunning
08-15-2012, 03:27 PM
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 mymastercraft.com. 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
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.

CantRepeat
05-18-2013, 04:22 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.


Thanks Engine Nut!!! I'll have to make this part of my clean up routine now.

sp00ky
05-18-2013, 11:00 PM
get yourself some gaskets when re-installing the headers or risers

Ok good to know

jslo
06-29-2013, 09:55 PM
Is 8 years considered reasonable service life for the factory manifolds? This 2005 mcx 5.7 started leaking at one of the welded plugs and the others look like they could go anytime.
And........the MC trailer is rusting to pieces under the boat.....all this after only 8 years of service. I fear I had too high expectations for the MC having owned other types of boats my whole life (I'm 53) and never had a trailer rust or a manifold go away with me.

snork
06-29-2013, 10:11 PM
depends where or what lake in texas you dunk your boat and trailer in

Gert
04-13-2015, 08:17 AM
*bump*
Old thread, but after wintersleep, when I visited my boat last saturday, I did find my MCX with two holes in the plugs of one exhaust manifold. Bummer, I am pretty sure I did not leave her this way last autumn...

The other plugs seems fine, even with a little stress from a hammer.

The boat is from 2004 and has 636 hours on the clock. Since 2009, the boat is mine where she did not see salt water. Before that? I don't know.

http://www.celica.dds.nl/plaatjes/prostar/exh/exh01.JPG


http://www.celica.dds.nl/plaatjes/prostar/exh/exh02.JPG


http://www.celica.dds.nl/plaatjes/prostar/exh/exh03.JPG

Next saturday she is going to an repairshop where they can weld aluminium. Lets hope I do not have to remove the manifold....

Engine Nut
04-13-2015, 09:22 AM
I suspect the manifold will have to come off. That damage is caused by electrolysis. The plug is more electrically active than the manifold so it acts like an anode. When water is in the manifold that has a high mineral content, the water acts as an electrolyte. If you remember back to 5th grade science, when two dissimilar metals are exposed to an electrolyte, a small amount of electrical current is produced and the anode is consumed.To prevent that from happening in the future, drain the manifolds by disconnecting the manifold crossover hose when the boat is going to sit for more than a couple of days.

Gert
04-13-2015, 09:50 AM
To prevent that from happening in the future, drain the manifolds by disconnecting the manifold crossover hose when the boat is going to sit for more than a couple of days.
I did see that. But, during winterizing I did not see anything. So since November last year, the manifold did not see any water. But eventhough, four of five months later the plugs are gone??

And, is every MCX having this problem or only some "mondaymorning" items?

Engine Nut
04-13-2015, 11:16 AM
I suspect that there was some water that didn't get drained from the manifold.

mikeg205
04-13-2015, 11:28 AM
There is another thread here showing the same issue on these manifolds.

seems like an issue over time - most marine manifolds are spec'd to last 500ish hours before they need to be replaced.

http://www.mastercraft.com/teamtalk/showthread.php?t=58715

Gert
04-22-2015, 10:44 AM
Holes are fixed now. Luckily the manifold could stay in place. A local truckshop took about 30 minutes to weld it. Pretty easy.

Welded:

http://www.celica.dds.nl/plaatjes/prostar/exh/exh04.JPG

Primering:

http://www.celica.dds.nl/plaatjes/prostar/exh/exh05.JPG

Back in color:

http://www.celica.dds.nl/plaatjes/prostar/exh/exh06.JPG

Me happy... :D