I have an Indmar MCX in my boat. I noted the other day that my exhaust manifold has some corrosion on it. It is occurring in these small little "caps" that have been welded into it. I think they are referred to as a sacrificial anode, but am unsure. In talking to Indmar, I'm told that this occurs because of electrolysis - the water interacting with the aluminum. He more or less implied that i should be draining the block after every time I ski. No one I know does this except at the end of the year to winterize their boat so the comment struck me as....odd. One of the caps corroded through the other day. I temporarily repaired it by slopping some JB Weld onto it.
The guy from Indmar further states that I should remove the manifolds, have them drilled out, and then have new caps welded in. Or, I can spend approximately $1,100 and get a new cast iron exhaust manifold set. I have no idea what kind of costs I'm going to run into having the manifolds, drilled, welded, and repainted only to have this happen again in approximately 6 or 7 years (my boat is an 05). Has anyone else experienced this? What did you do to correct the problem? With all the aluminum blocks out there now, will this be an issue for them as well?
Additionally, I'm concerned that because Indmar changed the exhaust in 06, that I'm going to have ECM issues with the cast iron exhaust (should I go that route). Is this concern unfounded?
thanks in advance for any insight or direction you can provide!
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There are others that have experienced it too, going the route of having them drilled and patched is the easiest and cheapest option. There were a couple of guys over on TT that used JB weld, but I wouldnt recomend doing that. IIRC there was also a guy selling a set of cast iron manifolds on there.
You can drill and tap the hole then install an anode that is threaded as opposed to welding one back in. Easy to replace once used up. They are available from Stainless Marine in Florida. You want the anode as it is the sacrificial element in the system, and hopefully not the manifold itself.
My old Nautique had a similar failure. I drilled out the hole and tapped in threads and screwed a bolt in with some silicone seal. This lasted quite well also.
I had to buy new manifolds for the American skier. That wasn't too hard either as I had used anti sieze on the manifold bolts during an earlier replacement.
Eric
A neighbors '06 MCX had same issue, I cut an aluminum disk the size of a quarter and used JB weld putty to hold it in place. It has held for almost a year now without issue.
The site that I've found cast iron manifolds the least expensive is SKIDIM.com yet it's still a good chunk of change that I'd rather put to something like a new ski. I believe i can find a place to weld in the new caps and feel that this would ultimately be a lot less expensive.
My follow up question is this: does it make sense to have the newly welded manifolds to be painted or powder coated? That should then prevent any kind of corrosion. Or would this be a bad thing for some reason?
http://www.mastercraft.com/teamtalk/showthread.php?t=21728&highlight=casting+plugs&page=4
The best protection you can do is flush the boat every time you finish up for the day. Ensure the boat has been run long enough for the thermostats to open, then put a dose of "Macs" through the engine.
The local river I ski at is semi salt, with a large ski/caravan park on it. Over the last summer we had 4 Malibu's go pop due to corrosion.
Obviously your engine will last a lot longer if it's used in only fresh water. But if it's in salt and you're not flushing it properly, you'll be lucky to get more than two seasons out of a set of manifolds (let alone the damage it's doing to the rest of the engine).