Rust stains leaking around muffler - Man Engines

How often do you hose down/wash your engine room? I usually do that every month or two.....depending on the boats usage. Also the hull air vent screens on the cabo are supposed to be taken out and washed every 100 hours. It most likely is the hose clamps rusting and leaking down. Try tightening them. There shouldn't be anything in your exhaust water to create rust stains on your Cabo. I also spray all brass and metals with a good corrosion guard monthly......like CRC or the one in the metal and bright dark blue can (forgot the name) it's pricier but works well......

Lightly rinse the engine, making sure to stay away from air intakes, valve cover breathers, electrical stuff......I sometimes use GUNK on the engines if they're dirty first......stay away from battery charger and exposed electrical stuff......but wash (soapy water) and rinse everything down.......the hull air filters are easy enough to pull out.......you could I suppose rinse them from the inside out......but if you think of all of the air the engines are ingesting and how much salt is in that air it gets on everything.......the water evaporates and the salt stays......mist the a/c's......while you're at it work all of the seacocks........when done (I shopvac the bilges dry) then start the engines and gen and let them run for 30 minutes so the engines burn all of the water off of them and the heat helps the moisture dissappate.......then go in and spray all your un-painted metals and brass with corrossion block.......

I would recommend that you check to see if you have anti-crush sleeves in your fiberglass before you overtighten the clamps. This is a stainless sleeve that fits inside the fiberglass so that it protects it from collapsing. I have seen a number of times that in an effort to stop a leak, clamps are tightened to the point that the now they have a fiberglass issue.

I found this photo showing what might happen if you over tighten a clamp. You can see that the fiberglass has collapsed at the lower clamp. Carl, I hope I have the attchment size correct.

So getting back to the subject of the thread for a momemt, I have 10 cylinder MANs one side showing similar rust. Is Daydreamer's explanation the correct one? Is the rust the result of a stainless steel sleeve at the union?

Can you post a photo for us to see?

It's not so much the Trident or any other maker of hose. It could be more that the fiberglass is out of round. As far as using a sealant, this reminds me of the old Fram commercial, "you can pay me now, or you can pay me later." Sooner or later, that hose connection is going to need to come out. A sealant will make this job much harder, not to mention the added cost of replacing the hose. I have also seen where clamps are not staggered to make a good seal.

I usually don't have to wash down the newer electronic engines, and do spot clean them a lot. BUT, I have rinsed them down, but only with a light mist, and have bagged the electrical harness connectors if need be. The problem is the salt air is still getting to them. There are some engine foamy degreasers that leave a nice protective residue like Gunk......I've used those and very lightly rinsed and have not had any ill effects on any yachts I've done it on.

Cold weather can causes silicone rubber hoses to contract slightly, and it looks like the hose clamps are loose. You can use a product called WHINK on the rust stains. Just put it on and let it sit 10 minutes, maybe lightly brush it and rinse it off.

Sorry to be a single issue guy here, but DayDreamer, you seem to be the only one on this thread who has actually looked "inside." Was your rust problem from a stainless steel insert? If so, is this a maintenance item in your opinion. My exhaust hoses have been connected to the mufflers for 12 years - what made you open yours?