Clacking Sound

1986 Mercruiser 305 (230 hp) Alpha One has a 'clacking sound' that I believe is shutters in the exhaust system.

Someone once said, long as they are clacking, they are not rusted in place and that is good.

What's the truth here?

Thanks,

Jeff

These would be the "back flow prevention" flappers.
Each pair of flapper plates hinge..... some in equal halves..... some in an "off-set" fashion with un-equal halves of the flapper to either side of the pin.
In any event, exhaust gasses will pass by/through without restriction.
Any back-flow water would come up against the flapper plates (from the oposite direction), causing the plates to close and restrict water from back-flowing.


IMO, if the flappers are in good condition, neither should be making an audible sound with the engine running.


.

Typically when you can hear them clacking it means the chickens have come home to roost.

Actually is because the rubber outer coating has come off and exposed the base material, Stainless steel and thus the clacking when the Stainless steel hit the aluminum exhaust tube.

Either live with the clacking or replace or just feed the dam things and that will shut them up!!

You could put a louder exhaust on her jeff.HA-HA

My daughter actually suggested that, so it would sound like a muscle boat! *She's a motor head and drives a 6 speed Mazda. Mighty proud of her!)

I assume the flappers require removal of the risers?

Jeff

PS: Looking for a drawing or some photos of the damn things. Got a Clymer manual, but you all know ho useless they are!

No elbows do not need removal... loosen all 4 hose clamps on rubber boots between elbow and down tubes and then the one below (both sides) and remove rubber tube and intermidiate aluminum tube. It takes finness and patiance but thats how it is done.
Look at the parts pages here for pictures.

http://www.marineengine.com/parts/m...9881995/0b525982-thru-0f600999/exhaust-system


This is for reference only....it is from an 350 motor 1988-1995. But it shows the basic idea and yoir should be the same if thru prop exhaust.