hole in exhaust bellows


Old 06-18-04, 07:05 PM
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hole in exhaust bellows

I have a 1977 mercruiser I/O with a inline 4 cylinder 120 hp motor. I noticed a rip in the exhaust bellows. What problems will this cause? Is it hard to replace?
would it cause overheating?
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Old 06-19-04, 07:11 AM
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Hello: Tom

A condition that should be corrected as soon as possible. Heat will expand any existing cracks and exhaust fumes are escaping into the engine compartment.

The escaping heat will prematurely cause excessive drying in the engine compartment and fumes to fill the same area. The exhaust manifold should be replaced asap.

Exhaust deterioration is a normal condition. Elbows likely to be the first effected as the hot fumes and exhaust gases hit the elbow directly than have to turn inside the elbow. Thus the concentration of hot gases and fumes heat the elbows more so than the straight pipe runs.

Not sure about overheating. Overheating the engine not likely but possible maybe. Overheating the engine compartment is a definite yes, expecially when the boat is not in motion. During that period of time, no incoming air is entering the engine compartment through the intake air vents.

Which is why the engine compartment has a ventilation system fan that should be run prior to starting the engine. To purge the engine compartment of any fumes which may accumulate during non usage periods, etc.

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Old 06-20-04, 07:04 AM
Join Date: Sep 2003
Location: cny
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are u talking about the bellows in the lower unit? are u sure it's not the u joint bellows? if it is, it must be replaced as soon as possible. need more info.
Old 06-20-04, 11:38 AM
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It is the bellows in the outdrive, I thought it directed the exhaust gasses out and down through the propeller hub. This was a guess, the bellows is (approx: 10in. long and 3in. in dia. with a ss.radiator type clamp on the distal end, and the end toward the transome appears to go into the transom).

In a shop manual(that reads like a cell phone with a weak signal) it shows a drawing of the drive bell-housing, and the label calls this tube, the exhaust bellows. It also shows a larger tube which is labled, bellows assembly. In the drawing it shows two clamps one on each end. Looking at my out drive I
can only see one clamp as noted.
Old 06-22-04, 02:53 PM
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BIG PROBLEM, That's pretty serious. Not only will the salt water wash out your u-joints and bearings and destroy them, but it will let water into the bilge and sink you.
Old 06-23-04, 06:26 PM
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Big problem, thats what I thought. Can an average mechanical type person fix this? How muchdo you think it would cost at a boat repair place? Thanks for the inputTom
Old 07-09-04, 12:56 PM
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What bellows is torn?The one missing the clamp or the other?
Old 08-05-04, 10:32 PM
Rane Havuk
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If it is the exhaust bellows outside of the boat then I don't believe there is a huge problem and it can be replaced if you're patient or at least more knowledgeable than me. If I remember correctly the exhaust bellows is the smaller hose and is below the larger drive shaft bellows. I think the the drive shaft bellows is about 4-5 inches in diameter(or at least larger than the exhaust bellows) and is above the exhaust bellows. If the drive bellows is torn then all the other posts are correct and it should be replaced immediatley and you would do well to service the bearings inside it(since the water may have washed them out). If it is the exhaust then I'm pretty sure there isn't much of a problem since exhaust just goes out a little farther along the line.

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