Mercruiser 4.3 Ratteling noise

[ian ash]

Hi there i own a boat with a 1990 4.3 mercruiser inboard engine and alpha one stern drive.When running her with mufs on today i noticed a ticking,knocking noise that seems to be coming from the bellhousing at the rear of the engine(whare the shaft goes through the hull).The noise is eratic at tickover as in a tick/knock noise every now and the but increases as the revs die down after reving engine.Its sort of like a metalic ratchity noise as the revs drop.I wouldnt say its realy loud but its quite loud.Its there wether in gear or out.
Any sugestions Thanks Ian Ash

 

[Aviator5]

Re: Mercruiser 4.3 Ratteling noise

Sounds like exhaust flaps.

 

[achris]

Re: Mercruiser 4.3 Ratteling noise

Sounds like it could be exhaust shutters clattering... Nothing to worry about...

C........

 

[ian ash]

Re: Mercruiser 4.3 Ratteling noise

Hi there Thanks for the advise. Iv just replaced manifolds and risers would this have any impact on the exhust shutters,as mor flow or something. The noise realy sounds quite nasty does the shutters ratteling sound so bad??
Cheers guys ian ash

 

[achris]

Re: Mercruiser 4.3 Ratteling noise

Shutter rattle can sound quite bad. Particularly when you've just gunned the engine and it's running down.

Chris.....

 

[ian ash]

Re: Mercruiser 4.3 Ratteling noise

Hi I take it the shutters are in the exhaust .But it sounds like the noise is coming from the bell housing on the engine is it possible the noise is tracking ?? Im just woried about expensive repair bills.iv just read a post now sugesting it may be a engine out job to replace shutters if the engine is older model.its a 1990 4.3 v6 carb model does any one know if this is true.
Cheers ian

 

[achris]

Re: Mercruiser 4.3 Ratteling noise

Exhaust shutters in that engine are in the top of the exhaust tube, just below the elbows. Access is by removing the elbows. The shutter rattle can sound like it's coming from the bell housing, because they are right next to each other.

Here's a picture of the shutters in the exhaust pipe. These particular shutters have been superseded by the later design (in the second picture) and they retrofit into the earlier pipe (yours)...

 

[Bondo]

Re: Mercruiser 4.3 Ratteling noise

Iv just replaced manifolds and risers would this have any impact on the exhust shutters,as mor flow or something. The noise realy sounds quite nasty does the shutters ratteling sound so bad??

Ayuh,... The shutters should have been Checked when the manifolds were done...

The motor has been run Dry,+ the exhaust has burnt the rubber off the shutters...
That's why they're Loud...

Eventually,... They'll fall off, into the transon, possibly blocking the flow...
But,... It'll be quieter...

 

[achris]

Re: Mercruiser 4.3 Ratteling noise

Ayuh,... The shutters should have been Checked when the manifolds were done...

The motor has been run Dry,+ the exhaust has burnt the rubber off the shutters...
That's why they're Loud...

Eventually,... They'll fall off, into the transon, possibly blocking the flow...
But,... It'll be quieter...

I thought (I could be wrong, again) that the original single plate shutter was not rubber covered...

 

[ian ash]

Re: Mercruiser 4.3 Ratteling noise

Hi there thanks for all your advise.Im having trouble finding a set of exhaust flappers in the uk. Does any one know the oem no. for exhaust flappers to fit 1990 v6 4.3 mercruiser carb version its 4 inch. Also is it possible to remove the elbow without removing the risers or y piece as iv just torqued down the risers and dont realy want to disturb them again!!
cheers guys ian

 

[N0 Luck]

Re: Mercruiser 4.3 Ratteling noise

shutters 807166A3 replaces 14348.... Trust me i was chasing that noise last week and it drove me crazy. thought I had a bad rocker, rod, lifter, gimble bearing... I chased each one until I realised there was shutters in there

Im actually replacing mine tomorrow

 

[ian ash]

Re: Mercruiser 4.3 Ratteling noise

Hi there!!

Bit of an update on the shutters!Took them out today and inspected them and found the rubber coating peeling away around the edges.Also the holes that the pin goes through is slightly elongated through ware.Run the engine without shutters in sounds sweet as a nut!No clanging noise.So ordering new shutters later,Not sure which ones to get yet, thinking about the pinless type(the ones with plastic stubs instead of pin and gromit)Anyone know if they are any good??.
Thanks for all your advise you were all spot on! all the best Ian

 

[Bondo]

Re: Mercruiser 4.3 Ratteling noise

I thought (I could be wrong, again) that the original single plate shutter was not rubber covered...

Ayuh,... So,... to use Bubba's line,... I guess I was Right, by accident...

 

[achris]

Re: Mercruiser 4.3 Ratteling noise

You can't get the old single plate type shutter any more... If you order the old style it supersedes to the retrofit new style. If you order the new style they will not fit... Look at these pictures to see why....