Exhaust flaps

[rinkman]

Ran my 4.3 liter Mercruiser on muffs this morning and noticed a rattling sound at idle. I have searched thru this forum and it seems as though maybe the exhaust flappers are rattling. The noise is coming from the rear area by the driveshaft. Is it bad to run with this rattle? From what I have read they are not hard to change. Do these normally go bad over time?

 

[stonyloam]

Re: Exhaust flaps

... seems as though maybe the exhaust flappers are rattling. The noise is coming from the rear area by the driveshaft. Is it bad to run with this rattle? From what I have read they are not hard to change. Do these normally go bad over time?

Could be the hinge on one of the shutters is torn and it is loose. If it is, it means that it is not doing its job and it could allow water to flow up into the exhaust, or they could brake free and partly block the exhaust. It would be wise to check. It was an hour to do one on my 470, if you can get to the clamps on the rubber exhaust tubes. They are rubber coated metal and the heat from the exhaust will cause them to become brittle and fail over time especially if they have ever been overheated. Good luck.